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Groups > linux.kernel > #1259147 > unrolled thread

[PATCH v4 0/6] virtio core DMA API conversion

Started byAndy Lutomirski <luto@kernel.org>
First post2015-10-30 02:20 +0100
Last post2015-10-30 11:00 +0100
Articles 11 — 4 participants

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Contents

  [PATCH v4 0/6] virtio core DMA API conversion Andy Lutomirski <luto@kernel.org> - 2015-10-30 02:20 +0100
    [PATCH v4 6/6] virtio_pci: Use the DMA API Andy Lutomirski <luto@kernel.org> - 2015-10-30 02:20 +0100
    Re: [PATCH v4 0/6] virtio core DMA API conversion Andy Lutomirski <luto@amacapital.net> - 2015-10-30 02:20 +0100
    [PATCH v4 5/6] virtio_mmio: Use the DMA API Andy Lutomirski <luto@kernel.org> - 2015-10-30 02:20 +0100
    [PATCH v4 3/6] virtio_pci: Use the DMA API Andy Lutomirski <luto@kernel.org> - 2015-10-30 02:20 +0100
    [PATCH v4 4/6] virtio: Add improved queue allocation API Andy Lutomirski <luto@kernel.org> - 2015-10-30 02:20 +0100
    [PATCH v4 2/6] virtio_ring: Support DMA APIs Andy Lutomirski <luto@kernel.org> - 2015-10-30 02:20 +0100
      Re: [PATCH v4 2/6] virtio_ring: Support DMA APIs Cornelia Huck <cornelia.huck@de.ibm.com> - 2015-10-30 13:10 +0100
        Re: [PATCH v4 2/6] virtio_ring: Support DMA APIs Christian Borntraeger <borntraeger@de.ibm.com> - 2015-10-30 13:10 +0100
          Re: [PATCH v4 2/6] virtio_ring: Support DMA APIs Andy Lutomirski <luto@amacapital.net> - 2015-10-30 20:00 +0100
    Re: [PATCH v4 0/6] virtio core DMA API conversion Christian Borntraeger <borntraeger@de.ibm.com> - 2015-10-30 11:00 +0100

#1259147 — [PATCH v4 0/6] virtio core DMA API conversion

FromAndy Lutomirski <luto@kernel.org>
Date2015-10-30 02:20 +0100
Subject[PATCH v4 0/6] virtio core DMA API conversion
Message-ID<qp6wh-7Kj-3@gated-at.bofh.it>
This switches virtio to use the DMA API unconditionally.  I'm sure
it breaks things, but it seems to work on x86 using virtio-pci, with
and without Xen, and using both the modern 1.0 variant and the
legacy variant.

This appears to work on native and Xen x86_64 using both modern and
legacy virtio-pci.  It also appears to work on arm and arm64.

It definitely won't work as-is on s390x, and I haven't been able to
test Christian's patches because I can't get virtio-ccw to work in
QEMU at all.  I don't know what I'm doing wrong.

It doesn't work on ppc64.  Ben, consider yourself pinged to send me
a patch :)

It doesn't work on sparc64.  I didn't realize at Kernel Summit that
sparc64 has the same problem as ppc64.

DaveM, for background, we're trying to fix virtio to use the DMA
API.  That will require that every platform that uses virtio
supplies valid DMA operations on devices that use virtio_ring.
Unfortunately, QEMU historically ignores the IOMMU on virtio
devices.

On x86, this isn't really a problem.  x86 has a nice way for the
platform to describe which devices are behind an IOMMU, and QEMU
will be adjusted accordingly.  The only thing that will break is a
recently-added experimental mode.

Ben's plan for powerpc is to add a quirk for existing virtio-pci
devices and to eventually update the devicetree stuff to allow QEMU
to tell the guest which devices use the IOMMU.

AFAICT sparc has a similar problem to powerpc.  DaveM, can you come
up with a straightforward way to get sparc's DMA API to work
correctly for virtio-pci devices?

NB: Sadly, the platforms I've successfully tested on don't include any
big-endian platforms, so there could still be lurking endian problems.

Changes from v3:
 - More big-endian fixes.
 - Added better virtio-ring APIs that handle allocation and use them in
   virtio-mmio and virtio-pci.
 - Switch to Michael's virtio-net patch.

Changes from v2:
 - Fix vring_mapping_error incorrect argument

Changes from v1:
 - Fix an endian conversion error causing a BUG to hit.
 - Fix a DMA ordering issue (swiotlb=force works now).
 - Minor cleanups.

Andy Lutomirski (5):
  virtio_ring: Support DMA APIs
  virtio_pci: Use the DMA API
  virtio: Add improved queue allocation API
  virtio_mmio: Use the DMA API
  virtio_pci: Use the DMA API

Michael S. Tsirkin (1):
  virtio-net: Stop doing DMA from the stack

 drivers/net/virtio_net.c           |  34 ++--
 drivers/virtio/Kconfig             |   2 +-
 drivers/virtio/virtio_mmio.c       |  67 ++-----
 drivers/virtio/virtio_pci_common.h |   6 -
 drivers/virtio/virtio_pci_legacy.c |  42 ++---
 drivers/virtio/virtio_pci_modern.c |  61 ++-----
 drivers/virtio/virtio_ring.c       | 348 ++++++++++++++++++++++++++++++-------
 include/linux/virtio.h             |  23 ++-
 include/linux/virtio_ring.h        |  35 ++++
 tools/virtio/linux/dma-mapping.h   |  17 ++
 10 files changed, 426 insertions(+), 209 deletions(-)
 create mode 100644 tools/virtio/linux/dma-mapping.h

-- 
2.4.3

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#1259148 — [PATCH v4 6/6] virtio_pci: Use the DMA API

FromAndy Lutomirski <luto@kernel.org>
Date2015-10-30 02:20 +0100
Subject[PATCH v4 6/6] virtio_pci: Use the DMA API
Message-ID<qp6wh-7Kj-5@gated-at.bofh.it>
In reply to#1259147
This switches to vring_create_virtqueue, simplifying the driver and
adding DMA API support.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
 drivers/virtio/virtio_pci_common.h |  7 -----
 drivers/virtio/virtio_pci_legacy.c | 39 +++++++-----------------
 drivers/virtio/virtio_pci_modern.c | 61 ++++++--------------------------------
 3 files changed, 19 insertions(+), 88 deletions(-)

diff --git a/drivers/virtio/virtio_pci_common.h b/drivers/virtio/virtio_pci_common.h
index cd6196b513ad..1a3c689d1b9e 100644
--- a/drivers/virtio/virtio_pci_common.h
+++ b/drivers/virtio/virtio_pci_common.h
@@ -35,13 +35,6 @@ struct virtio_pci_vq_info {
 	/* the actual virtqueue */
 	struct virtqueue *vq;
 
-	/* the number of entries in the queue */
-	int num;
-
-	/* the ring queue */
-	void *queue;
-	dma_addr_t queue_dma_addr;      /* bus address */
-
 	/* the list node for the virtqueues list */
 	struct list_head node;
 
diff --git a/drivers/virtio/virtio_pci_legacy.c b/drivers/virtio/virtio_pci_legacy.c
index b5293e5f2af4..8c4e61783441 100644
--- a/drivers/virtio/virtio_pci_legacy.c
+++ b/drivers/virtio/virtio_pci_legacy.c
@@ -119,7 +119,6 @@ static struct virtqueue *setup_vq(struct virtio_pci_device *vp_dev,
 				  u16 msix_vec)
 {
 	struct virtqueue *vq;
-	unsigned long size;
 	u16 num;
 	int err;
 
@@ -131,29 +130,19 @@ static struct virtqueue *setup_vq(struct virtio_pci_device *vp_dev,
 	if (!num || ioread32(vp_dev->ioaddr + VIRTIO_PCI_QUEUE_PFN))
 		return ERR_PTR(-ENOENT);
 
-	info->num = num;
 	info->msix_vector = msix_vec;
 
-	size = PAGE_ALIGN(vring_size(num, VIRTIO_PCI_VRING_ALIGN));
-	info->queue = dma_zalloc_coherent(&vp_dev->pci_dev->dev, size,
-					  &info->queue_dma_addr,
-					  GFP_KERNEL);
-	if (info->queue == NULL)
+	/* create the vring */
+	vq = vring_create_virtqueue(index, num,
+				    VIRTIO_PCI_VRING_ALIGN, &vp_dev->vdev,
+				    true, false, vp_notify, callback, name);
+	if (!vq)
 		return ERR_PTR(-ENOMEM);
 
 	/* activate the queue */
-	iowrite32(info->queue_dma_addr >> VIRTIO_PCI_QUEUE_ADDR_SHIFT,
+	iowrite32(virtqueue_get_desc_addr(vq) >> VIRTIO_PCI_QUEUE_ADDR_SHIFT,
 		  vp_dev->ioaddr + VIRTIO_PCI_QUEUE_PFN);
 
-	/* create the vring */
-	vq = vring_new_virtqueue(index, info->num,
-				 VIRTIO_PCI_VRING_ALIGN, &vp_dev->vdev,
-				 true, info->queue, vp_notify, callback, name);
-	if (!vq) {
-		err = -ENOMEM;
-		goto out_activate_queue;
-	}
-
 	vq->priv = (void __force *)vp_dev->ioaddr + VIRTIO_PCI_QUEUE_NOTIFY;
 
 	if (msix_vec != VIRTIO_MSI_NO_VECTOR) {
@@ -161,18 +150,15 @@ static struct virtqueue *setup_vq(struct virtio_pci_device *vp_dev,
 		msix_vec = ioread16(vp_dev->ioaddr + VIRTIO_MSI_QUEUE_VECTOR);
 		if (msix_vec == VIRTIO_MSI_NO_VECTOR) {
 			err = -EBUSY;
-			goto out_assign;
+			goto out_deactivate;
 		}
 	}
 
 	return vq;
 
-out_assign:
-	vring_del_virtqueue(vq);
-out_activate_queue:
+out_deactivate:
 	iowrite32(0, vp_dev->ioaddr + VIRTIO_PCI_QUEUE_PFN);
-	dma_free_coherent(&vp_dev->pci_dev->dev, size,
-			  info->queue, info->queue_dma_addr);
+	vring_del_virtqueue(vq);
 	return ERR_PTR(err);
 }
 
@@ -180,7 +166,6 @@ static void del_vq(struct virtio_pci_vq_info *info)
 {
 	struct virtqueue *vq = info->vq;
 	struct virtio_pci_device *vp_dev = to_vp_device(vq->vdev);
-	unsigned long size;
 
 	iowrite16(vq->index, vp_dev->ioaddr + VIRTIO_PCI_QUEUE_SEL);
 
@@ -191,14 +176,10 @@ static void del_vq(struct virtio_pci_vq_info *info)
 		ioread8(vp_dev->ioaddr + VIRTIO_PCI_ISR);
 	}
 
-	vring_del_virtqueue(vq);
-
 	/* Select and deactivate the queue */
 	iowrite32(0, vp_dev->ioaddr + VIRTIO_PCI_QUEUE_PFN);
 
-	size = PAGE_ALIGN(vring_size(info->num, VIRTIO_PCI_VRING_ALIGN));
-	dma_free_coherent(&vp_dev->pci_dev->dev, size,
-			  info->queue, info->queue_dma_addr);
+	vring_del_virtqueue(vq);
 }
 
 static const struct virtio_config_ops virtio_pci_config_ops = {
diff --git a/drivers/virtio/virtio_pci_modern.c b/drivers/virtio/virtio_pci_modern.c
index fbe0bd1c4881..50b0cd5a501e 100644
--- a/drivers/virtio/virtio_pci_modern.c
+++ b/drivers/virtio/virtio_pci_modern.c
@@ -287,35 +287,6 @@ static u16 vp_config_vector(struct virtio_pci_device *vp_dev, u16 vector)
 	return vp_ioread16(&vp_dev->common->msix_config);
 }
 
-static size_t vring_pci_size(u16 num)
-{
-	/* We only need a cacheline separation. */
-	return PAGE_ALIGN(vring_size(num, SMP_CACHE_BYTES));
-}
-
-static void *alloc_virtqueue_pages(struct virtio_pci_device *vp_dev,
-				   int *num, dma_addr_t *dma_addr)
-{
-	void *pages;
-
-	/* TODO: allocate each queue chunk individually */
-	for (; *num && vring_pci_size(*num) > PAGE_SIZE; *num /= 2) {
-		pages = dma_zalloc_coherent(
-			&vp_dev->pci_dev->dev, vring_pci_size(*num),
-			dma_addr, GFP_KERNEL|__GFP_NOWARN);
-		if (pages)
-			return pages;
-	}
-
-	if (!*num)
-		return NULL;
-
-	/* Try to get a single page. You are my only hope! */
-	return dma_zalloc_coherent(
-		&vp_dev->pci_dev->dev, vring_pci_size(*num),
-		dma_addr, GFP_KERNEL);
-}
-
 static struct virtqueue *setup_vq(struct virtio_pci_device *vp_dev,
 				  struct virtio_pci_vq_info *info,
 				  unsigned index,
@@ -347,30 +318,22 @@ static struct virtqueue *setup_vq(struct virtio_pci_device *vp_dev,
 	/* get offset of notification word for this vq */
 	off = vp_ioread16(&cfg->queue_notify_off);
 
-	info->num = num;
 	info->msix_vector = msix_vec;
 
-	info->queue = alloc_virtqueue_pages(vp_dev, &info->num,
-					    &info->queue_dma_addr);
-	if (info->queue == NULL)
-		return ERR_PTR(-ENOMEM);
-
 	/* create the vring */
-	vq = vring_new_virtqueue(index, info->num,
-				 SMP_CACHE_BYTES, &vp_dev->vdev,
-				 true, info->queue, vp_notify, callback, name);
-	if (!vq) {
-		err = -ENOMEM;
-		goto err_new_queue;
-	}
+	vq = vring_create_virtqueue(index, num,
+				    SMP_CACHE_BYTES, &vp_dev->vdev,
+				    true, true, vp_notify, callback, name);
+	if (!vq)
+		return ERR_PTR(-ENOMEM);
 
 	/* activate the queue */
-	vp_iowrite16(num, &cfg->queue_size);
-	vp_iowrite64_twopart(info->queue_dma_addr,
+	vp_iowrite16(virtqueue_get_vring_size(vq), &cfg->queue_size);
+	vp_iowrite64_twopart(virtqueue_get_desc_addr(vq),
 			     &cfg->queue_desc_lo, &cfg->queue_desc_hi);
-	vp_iowrite64_twopart(info->queue_dma_addr + ((char *)virtqueue_get_avail(vq) - (char *)info->queue),
+	vp_iowrite64_twopart(virtqueue_get_avail_addr(vq),
 			     &cfg->queue_avail_lo, &cfg->queue_avail_hi);
-	vp_iowrite64_twopart(info->queue_dma_addr + ((char *)virtqueue_get_used(vq) - (char *)info->queue),
+	vp_iowrite64_twopart(virtqueue_get_used_addr(vq),
 			     &cfg->queue_used_lo, &cfg->queue_used_hi);
 
 	if (vp_dev->notify_base) {
@@ -415,9 +378,6 @@ err_assign_vector:
 		pci_iounmap(vp_dev->pci_dev, (void __iomem __force *)vq->priv);
 err_map_notify:
 	vring_del_virtqueue(vq);
-err_new_queue:
-	dma_free_coherent(&vp_dev->pci_dev->dev, vring_pci_size(info->num),
-			  info->queue, info->queue_dma_addr);
 	return ERR_PTR(err);
 }
 
@@ -462,9 +422,6 @@ static void del_vq(struct virtio_pci_vq_info *info)
 		pci_iounmap(vp_dev->pci_dev, (void __force __iomem *)vq->priv);
 
 	vring_del_virtqueue(vq);
-
-	dma_free_coherent(&vp_dev->pci_dev->dev, vring_pci_size(info->num),
-			  info->queue, info->queue_dma_addr);
 }
 
 static const struct virtio_config_ops virtio_pci_config_nodev_ops = {
-- 
2.4.3

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#1259149

FromAndy Lutomirski <luto@amacapital.net>
Date2015-10-30 02:20 +0100
Message-ID<qp6wh-7Kj-7@gated-at.bofh.it>
In reply to#1259147
On Thu, Oct 29, 2015 at 6:09 PM, Andy Lutomirski <luto@kernel.org> wrote:
> This switches virtio to use the DMA API unconditionally.  I'm sure
> it breaks things, but it seems to work on x86 using virtio-pci, with
> and without Xen, and using both the modern 1.0 variant and the
> legacy variant.

...

> Andy Lutomirski (5):
>   virtio_ring: Support DMA APIs
>   virtio_pci: Use the DMA API
>   virtio: Add improved queue allocation API
>   virtio_mmio: Use the DMA API
>   virtio_pci: Use the DMA API

Ugh.  The two virtio_pci patches should be squashed together.  I'll do
that for v5, but I'm not going to send it until there's more feedback.

FWIW, I'm collecting this stuff here:

https://git.kernel.org/cgit/linux/kernel/git/luto/linux.git/log/?h=virtio_dma

That branch includes this series (with the squash) and the s390
patches.  I'll keep it up to date, since it seems silly to declare it
stable enough to stop rebasing yet.

--Andy
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#1259150 — [PATCH v4 5/6] virtio_mmio: Use the DMA API

FromAndy Lutomirski <luto@kernel.org>
Date2015-10-30 02:20 +0100
Subject[PATCH v4 5/6] virtio_mmio: Use the DMA API
Message-ID<qp6wh-7Kj-9@gated-at.bofh.it>
In reply to#1259147
This switches to vring_create_virtqueue, simplifying the driver and
adding DMA API support.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
 drivers/virtio/virtio_mmio.c | 67 ++++++++++----------------------------------
 1 file changed, 15 insertions(+), 52 deletions(-)

diff --git a/drivers/virtio/virtio_mmio.c b/drivers/virtio/virtio_mmio.c
index f499d9da7237..2b9fab52a3cb 100644
--- a/drivers/virtio/virtio_mmio.c
+++ b/drivers/virtio/virtio_mmio.c
@@ -99,12 +99,6 @@ struct virtio_mmio_vq_info {
 	/* the actual virtqueue */
 	struct virtqueue *vq;
 
-	/* the number of entries in the queue */
-	unsigned int num;
-
-	/* the virtual address of the ring queue */
-	void *queue;
-
 	/* the list node for the virtqueues list */
 	struct list_head node;
 };
@@ -322,15 +316,13 @@ static void vm_del_vq(struct virtqueue *vq)
 {
 	struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vq->vdev);
 	struct virtio_mmio_vq_info *info = vq->priv;
-	unsigned long flags, size;
+	unsigned long flags;
 	unsigned int index = vq->index;
 
 	spin_lock_irqsave(&vm_dev->lock, flags);
 	list_del(&info->node);
 	spin_unlock_irqrestore(&vm_dev->lock, flags);
 
-	vring_del_virtqueue(vq);
-
 	/* Select and deactivate the queue */
 	writel(index, vm_dev->base + VIRTIO_MMIO_QUEUE_SEL);
 	if (vm_dev->version == 1) {
@@ -340,8 +332,8 @@ static void vm_del_vq(struct virtqueue *vq)
 		WARN_ON(readl(vm_dev->base + VIRTIO_MMIO_QUEUE_READY));
 	}
 
-	size = PAGE_ALIGN(vring_size(info->num, VIRTIO_MMIO_VRING_ALIGN));
-	free_pages_exact(info->queue, size);
+	vring_del_virtqueue(vq);
+
 	kfree(info);
 }
 
@@ -356,8 +348,6 @@ static void vm_del_vqs(struct virtio_device *vdev)
 	free_irq(platform_get_irq(vm_dev->pdev, 0), vm_dev);
 }
 
-
-
 static struct virtqueue *vm_setup_vq(struct virtio_device *vdev, unsigned index,
 				  void (*callback)(struct virtqueue *vq),
 				  const char *name)
@@ -365,7 +355,8 @@ static struct virtqueue *vm_setup_vq(struct virtio_device *vdev, unsigned index,
 	struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
 	struct virtio_mmio_vq_info *info;
 	struct virtqueue *vq;
-	unsigned long flags, size;
+	unsigned long flags;
+	unsigned int num;
 	int err;
 
 	if (!name)
@@ -388,66 +379,40 @@ static struct virtqueue *vm_setup_vq(struct virtio_device *vdev, unsigned index,
 		goto error_kmalloc;
 	}
 
-	/* Allocate pages for the queue - start with a queue as big as
-	 * possible (limited by maximum size allowed by device), drop down
-	 * to a minimal size, just big enough to fit descriptor table
-	 * and two rings (which makes it "alignment_size * 2")
-	 */
-	info->num = readl(vm_dev->base + VIRTIO_MMIO_QUEUE_NUM_MAX);
-
-	/* If the device reports a 0 entry queue, we won't be able to
-	 * use it to perform I/O, and vring_new_virtqueue() can't create
-	 * empty queues anyway, so don't bother to set up the device.
-	 */
-	if (info->num == 0) {
+	num = readl(vm_dev->base + VIRTIO_MMIO_QUEUE_NUM_MAX);
+	if (num == 0) {
 		err = -ENOENT;
-		goto error_alloc_pages;
-	}
-
-	while (1) {
-		size = PAGE_ALIGN(vring_size(info->num,
-				VIRTIO_MMIO_VRING_ALIGN));
-		/* Did the last iter shrink the queue below minimum size? */
-		if (size < VIRTIO_MMIO_VRING_ALIGN * 2) {
-			err = -ENOMEM;
-			goto error_alloc_pages;
-		}
-
-		info->queue = alloc_pages_exact(size, GFP_KERNEL | __GFP_ZERO);
-		if (info->queue)
-			break;
-
-		info->num /= 2;
+		goto error_new_virtqueue;
 	}
 
 	/* Create the vring */
-	vq = vring_new_virtqueue(index, info->num, VIRTIO_MMIO_VRING_ALIGN, vdev,
-				 true, info->queue, vm_notify, callback, name);
+	vq = vring_create_virtqueue(index, num, VIRTIO_MMIO_VRING_ALIGN, vdev,
+				 true, true, vm_notify, callback, name);
 	if (!vq) {
 		err = -ENOMEM;
 		goto error_new_virtqueue;
 	}
 
 	/* Activate the queue */
-	writel(info->num, vm_dev->base + VIRTIO_MMIO_QUEUE_NUM);
+	writel(virtqueue_get_vring_size(vq), vm_dev->base + VIRTIO_MMIO_QUEUE_NUM);
 	if (vm_dev->version == 1) {
 		writel(PAGE_SIZE, vm_dev->base + VIRTIO_MMIO_QUEUE_ALIGN);
-		writel(virt_to_phys(info->queue) >> PAGE_SHIFT,
+		writel(virtqueue_get_desc_addr(vq) >> PAGE_SHIFT,
 				vm_dev->base + VIRTIO_MMIO_QUEUE_PFN);
 	} else {
 		u64 addr;
 
-		addr = virt_to_phys(info->queue);
+		addr = virtqueue_get_desc_addr(vq);
 		writel((u32)addr, vm_dev->base + VIRTIO_MMIO_QUEUE_DESC_LOW);
 		writel((u32)(addr >> 32),
 				vm_dev->base + VIRTIO_MMIO_QUEUE_DESC_HIGH);
 
-		addr = virt_to_phys(virtqueue_get_avail(vq));
+		addr = virtqueue_get_avail_addr(vq);
 		writel((u32)addr, vm_dev->base + VIRTIO_MMIO_QUEUE_AVAIL_LOW);
 		writel((u32)(addr >> 32),
 				vm_dev->base + VIRTIO_MMIO_QUEUE_AVAIL_HIGH);
 
-		addr = virt_to_phys(virtqueue_get_used(vq));
+		addr = virtqueue_get_used_addr(vq);
 		writel((u32)addr, vm_dev->base + VIRTIO_MMIO_QUEUE_USED_LOW);
 		writel((u32)(addr >> 32),
 				vm_dev->base + VIRTIO_MMIO_QUEUE_USED_HIGH);
@@ -471,8 +436,6 @@ error_new_virtqueue:
 		writel(0, vm_dev->base + VIRTIO_MMIO_QUEUE_READY);
 		WARN_ON(readl(vm_dev->base + VIRTIO_MMIO_QUEUE_READY));
 	}
-	free_pages_exact(info->queue, size);
-error_alloc_pages:
 	kfree(info);
 error_kmalloc:
 error_available:
-- 
2.4.3

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#1259152 — [PATCH v4 3/6] virtio_pci: Use the DMA API

FromAndy Lutomirski <luto@kernel.org>
Date2015-10-30 02:20 +0100
Subject[PATCH v4 3/6] virtio_pci: Use the DMA API
Message-ID<qp6wi-7Kj-15@gated-at.bofh.it>
In reply to#1259147
This fixes virtio-pci on platforms and busses that have IOMMUs.  This
will break the experimental QEMU Q35 IOMMU support until QEMU is
fixed.  In exchange, it fixes physical virtio hardware as well as
virtio-pci running under Xen.

We should clean up the virtqueue API to do its own allocation and
teach virtqueue_get_avail and virtqueue_get_used to return DMA
addresses directly.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
 drivers/virtio/virtio_pci_common.h |  3 ++-
 drivers/virtio/virtio_pci_legacy.c | 19 +++++++++++++++----
 drivers/virtio/virtio_pci_modern.c | 34 ++++++++++++++++++++++++----------
 3 files changed, 41 insertions(+), 15 deletions(-)

diff --git a/drivers/virtio/virtio_pci_common.h b/drivers/virtio/virtio_pci_common.h
index b976d968e793..cd6196b513ad 100644
--- a/drivers/virtio/virtio_pci_common.h
+++ b/drivers/virtio/virtio_pci_common.h
@@ -38,8 +38,9 @@ struct virtio_pci_vq_info {
 	/* the number of entries in the queue */
 	int num;
 
-	/* the virtual address of the ring queue */
+	/* the ring queue */
 	void *queue;
+	dma_addr_t queue_dma_addr;      /* bus address */
 
 	/* the list node for the virtqueues list */
 	struct list_head node;
diff --git a/drivers/virtio/virtio_pci_legacy.c b/drivers/virtio/virtio_pci_legacy.c
index 48bc9797e530..b5293e5f2af4 100644
--- a/drivers/virtio/virtio_pci_legacy.c
+++ b/drivers/virtio/virtio_pci_legacy.c
@@ -135,12 +135,14 @@ static struct virtqueue *setup_vq(struct virtio_pci_device *vp_dev,
 	info->msix_vector = msix_vec;
 
 	size = PAGE_ALIGN(vring_size(num, VIRTIO_PCI_VRING_ALIGN));
-	info->queue = alloc_pages_exact(size, GFP_KERNEL|__GFP_ZERO);
+	info->queue = dma_zalloc_coherent(&vp_dev->pci_dev->dev, size,
+					  &info->queue_dma_addr,
+					  GFP_KERNEL);
 	if (info->queue == NULL)
 		return ERR_PTR(-ENOMEM);
 
 	/* activate the queue */
-	iowrite32(virt_to_phys(info->queue) >> VIRTIO_PCI_QUEUE_ADDR_SHIFT,
+	iowrite32(info->queue_dma_addr >> VIRTIO_PCI_QUEUE_ADDR_SHIFT,
 		  vp_dev->ioaddr + VIRTIO_PCI_QUEUE_PFN);
 
 	/* create the vring */
@@ -169,7 +171,8 @@ out_assign:
 	vring_del_virtqueue(vq);
 out_activate_queue:
 	iowrite32(0, vp_dev->ioaddr + VIRTIO_PCI_QUEUE_PFN);
-	free_pages_exact(info->queue, size);
+	dma_free_coherent(&vp_dev->pci_dev->dev, size,
+			  info->queue, info->queue_dma_addr);
 	return ERR_PTR(err);
 }
 
@@ -194,7 +197,8 @@ static void del_vq(struct virtio_pci_vq_info *info)
 	iowrite32(0, vp_dev->ioaddr + VIRTIO_PCI_QUEUE_PFN);
 
 	size = PAGE_ALIGN(vring_size(info->num, VIRTIO_PCI_VRING_ALIGN));
-	free_pages_exact(info->queue, size);
+	dma_free_coherent(&vp_dev->pci_dev->dev, size,
+			  info->queue, info->queue_dma_addr);
 }
 
 static const struct virtio_config_ops virtio_pci_config_ops = {
@@ -227,6 +231,13 @@ int virtio_pci_legacy_probe(struct virtio_pci_device *vp_dev)
 		return -ENODEV;
 	}
 
+	rc = dma_set_mask_and_coherent(&pci_dev->dev, DMA_BIT_MASK(64));
+	if (rc)
+		rc = dma_set_mask_and_coherent(&pci_dev->dev,
+						DMA_BIT_MASK(32));
+	if (rc)
+		dev_warn(&pci_dev->dev, "Failed to enable 64-bit or 32-bit DMA.  Trying to continue, but this might not work.\n");
+
 	rc = pci_request_region(pci_dev, 0, "virtio-pci-legacy");
 	if (rc)
 		return rc;
diff --git a/drivers/virtio/virtio_pci_modern.c b/drivers/virtio/virtio_pci_modern.c
index 8e5cf194cc0b..fbe0bd1c4881 100644
--- a/drivers/virtio/virtio_pci_modern.c
+++ b/drivers/virtio/virtio_pci_modern.c
@@ -293,14 +293,16 @@ static size_t vring_pci_size(u16 num)
 	return PAGE_ALIGN(vring_size(num, SMP_CACHE_BYTES));
 }
 
-static void *alloc_virtqueue_pages(int *num)
+static void *alloc_virtqueue_pages(struct virtio_pci_device *vp_dev,
+				   int *num, dma_addr_t *dma_addr)
 {
 	void *pages;
 
 	/* TODO: allocate each queue chunk individually */
 	for (; *num && vring_pci_size(*num) > PAGE_SIZE; *num /= 2) {
-		pages = alloc_pages_exact(vring_pci_size(*num),
-					  GFP_KERNEL|__GFP_ZERO|__GFP_NOWARN);
+		pages = dma_zalloc_coherent(
+			&vp_dev->pci_dev->dev, vring_pci_size(*num),
+			dma_addr, GFP_KERNEL|__GFP_NOWARN);
 		if (pages)
 			return pages;
 	}
@@ -309,7 +311,9 @@ static void *alloc_virtqueue_pages(int *num)
 		return NULL;
 
 	/* Try to get a single page. You are my only hope! */
-	return alloc_pages_exact(vring_pci_size(*num), GFP_KERNEL|__GFP_ZERO);
+	return dma_zalloc_coherent(
+		&vp_dev->pci_dev->dev, vring_pci_size(*num),
+		dma_addr, GFP_KERNEL);
 }
 
 static struct virtqueue *setup_vq(struct virtio_pci_device *vp_dev,
@@ -346,7 +350,8 @@ static struct virtqueue *setup_vq(struct virtio_pci_device *vp_dev,
 	info->num = num;
 	info->msix_vector = msix_vec;
 
-	info->queue = alloc_virtqueue_pages(&info->num);
+	info->queue = alloc_virtqueue_pages(vp_dev, &info->num,
+					    &info->queue_dma_addr);
 	if (info->queue == NULL)
 		return ERR_PTR(-ENOMEM);
 
@@ -361,11 +366,11 @@ static struct virtqueue *setup_vq(struct virtio_pci_device *vp_dev,
 
 	/* activate the queue */
 	vp_iowrite16(num, &cfg->queue_size);
-	vp_iowrite64_twopart(virt_to_phys(info->queue),
+	vp_iowrite64_twopart(info->queue_dma_addr,
 			     &cfg->queue_desc_lo, &cfg->queue_desc_hi);
-	vp_iowrite64_twopart(virt_to_phys(virtqueue_get_avail(vq)),
+	vp_iowrite64_twopart(info->queue_dma_addr + ((char *)virtqueue_get_avail(vq) - (char *)info->queue),
 			     &cfg->queue_avail_lo, &cfg->queue_avail_hi);
-	vp_iowrite64_twopart(virt_to_phys(virtqueue_get_used(vq)),
+	vp_iowrite64_twopart(info->queue_dma_addr + ((char *)virtqueue_get_used(vq) - (char *)info->queue),
 			     &cfg->queue_used_lo, &cfg->queue_used_hi);
 
 	if (vp_dev->notify_base) {
@@ -411,7 +416,8 @@ err_assign_vector:
 err_map_notify:
 	vring_del_virtqueue(vq);
 err_new_queue:
-	free_pages_exact(info->queue, vring_pci_size(info->num));
+	dma_free_coherent(&vp_dev->pci_dev->dev, vring_pci_size(info->num),
+			  info->queue, info->queue_dma_addr);
 	return ERR_PTR(err);
 }
 
@@ -457,7 +463,8 @@ static void del_vq(struct virtio_pci_vq_info *info)
 
 	vring_del_virtqueue(vq);
 
-	free_pages_exact(info->queue, vring_pci_size(info->num));
+	dma_free_coherent(&vp_dev->pci_dev->dev, vring_pci_size(info->num),
+			  info->queue, info->queue_dma_addr);
 }
 
 static const struct virtio_config_ops virtio_pci_config_nodev_ops = {
@@ -641,6 +648,13 @@ int virtio_pci_modern_probe(struct virtio_pci_device *vp_dev)
 		return -EINVAL;
 	}
 
+	err = dma_set_mask_and_coherent(&pci_dev->dev, DMA_BIT_MASK(64));
+	if (err)
+		err = dma_set_mask_and_coherent(&pci_dev->dev,
+						DMA_BIT_MASK(32));
+	if (err)
+		dev_warn(&pci_dev->dev, "Failed to enable 64-bit or 32-bit DMA.  Trying to continue, but this might not work.\n");
+
 	/* Device capability is only mandatory for devices that have
 	 * device-specific configuration.
 	 */
-- 
2.4.3

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#1259153 — [PATCH v4 4/6] virtio: Add improved queue allocation API

FromAndy Lutomirski <luto@kernel.org>
Date2015-10-30 02:20 +0100
Subject[PATCH v4 4/6] virtio: Add improved queue allocation API
Message-ID<qp6wi-7Kj-17@gated-at.bofh.it>
In reply to#1259147
This leaves vring_new_virtqueue alone for compatbility, but it
adds two new improved APIs:

vring_create_virtqueue: Creates a virtqueue backed by automatically
allocated coherent memory.  (Some day it this could be extended to
support non-coherent memory, too, if there ends up being a platform
on which it's worthwhile.)

__vring_new_virtqueue: Creates a virtqueue with a manually-specified
layout.  This should allow mic_virtio to work much more cleanly.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
 drivers/virtio/virtio_ring.c | 164 +++++++++++++++++++++++++++++++++++--------
 include/linux/virtio.h       |  23 +++++-
 include/linux/virtio_ring.h  |  35 +++++++++
 3 files changed, 190 insertions(+), 32 deletions(-)

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index a872eb89587f..f269e1cba00c 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -91,6 +91,11 @@ struct vring_virtqueue
 	/* How to notify other side. FIXME: commonalize hcalls! */
 	bool (*notify)(struct virtqueue *vq);
 
+	/* DMA, allocation, and size information */
+	bool we_own_ring;
+	size_t queue_size_in_bytes;
+	dma_addr_t queue_dma_addr;
+
 #ifdef DEBUG
 	/* They're supposed to lock for us. */
 	unsigned int in_use;
@@ -821,36 +826,31 @@ irqreturn_t vring_interrupt(int irq, void *_vq)
 }
 EXPORT_SYMBOL_GPL(vring_interrupt);
 
-struct virtqueue *vring_new_virtqueue(unsigned int index,
-				      unsigned int num,
-				      unsigned int vring_align,
-				      struct virtio_device *vdev,
-				      bool weak_barriers,
-				      void *pages,
-				      bool (*notify)(struct virtqueue *),
-				      void (*callback)(struct virtqueue *),
-				      const char *name)
+struct virtqueue *__vring_new_virtqueue(unsigned int index,
+					struct vring vring,
+					struct virtio_device *vdev,
+					bool weak_barriers,
+					bool (*notify)(struct virtqueue *),
+					void (*callback)(struct virtqueue *),
+					const char *name)
 {
-	struct vring_virtqueue *vq;
 	unsigned int i;
+	struct vring_virtqueue *vq;
 
-	/* We assume num is a power of 2. */
-	if (num & (num - 1)) {
-		dev_warn(&vdev->dev, "Bad virtqueue length %u\n", num);
-		return NULL;
-	}
-
-	vq = kmalloc(sizeof(*vq) + num * sizeof(struct vring_desc_state),
+	vq = kmalloc(sizeof(*vq) + vring.num * sizeof(struct vring_desc_state),
 		     GFP_KERNEL);
 	if (!vq)
 		return NULL;
 
-	vring_init(&vq->vring, num, pages, vring_align);
+	vq->vring = vring;
 	vq->vq.callback = callback;
 	vq->vq.vdev = vdev;
 	vq->vq.name = name;
-	vq->vq.num_free = num;
+	vq->vq.num_free = vring.num;
 	vq->vq.index = index;
+	vq->we_own_ring = false;
+	vq->queue_dma_addr = 0;
+	vq->queue_size_in_bytes = 0;
 	vq->notify = notify;
 	vq->weak_barriers = weak_barriers;
 	vq->broken = false;
@@ -871,18 +871,105 @@ struct virtqueue *vring_new_virtqueue(unsigned int index,
 
 	/* Put everything in free lists. */
 	vq->free_head = 0;
-	for (i = 0; i < num-1; i++)
+	for (i = 0; i < vring.num-1; i++)
 		vq->vring.desc[i].next = cpu_to_virtio16(vdev, i + 1);
-	memset(vq->desc_state, 0, num * sizeof(struct vring_desc_state));
+	memset(vq->desc_state, 0, vring.num * sizeof(struct vring_desc_state));
 
 	return &vq->vq;
 }
+EXPORT_SYMBOL_GPL(__vring_new_virtqueue);
+
+struct virtqueue *vring_create_virtqueue(
+	unsigned int index,
+	unsigned int num,
+	unsigned int vring_align,
+	struct virtio_device *vdev,
+	bool weak_barriers,
+	bool may_reduce_num,
+	bool (*notify)(struct virtqueue *),
+	void (*callback)(struct virtqueue *),
+	const char *name)
+{
+	struct virtqueue *vq;
+	void *queue;
+	dma_addr_t dma_addr;
+	size_t queue_size_in_bytes;
+	struct vring vring;
+
+	/* We assume num is a power of 2. */
+	if (num & (num - 1)) {
+		dev_warn(&vdev->dev, "Bad virtqueue length %u\n", num);
+		return NULL;
+	}
+
+	/* TODO: allocate each queue chunk individually */
+	for (; num && vring_size(num, vring_align) > PAGE_SIZE; num /= 2) {
+		queue = dma_zalloc_coherent(
+			vdev->dev.parent, vring_size(num, vring_align),
+			&dma_addr, GFP_KERNEL|__GFP_NOWARN);
+		if (queue)
+			break;
+	}
+
+	if (!num)
+		return NULL;
+
+	if (!queue) {
+		/* Try to get a single page. You are my only hope! */
+		queue = dma_zalloc_coherent(
+			vdev->dev.parent, vring_size(num, vring_align),
+			&dma_addr, GFP_KERNEL);
+	}
+	if (!queue)
+		return NULL;
+
+	queue_size_in_bytes = vring_size(num, vring_align);
+	vring_init(&vring, num, queue, vring_align);
+
+	vq = __vring_new_virtqueue(index, vring, vdev, weak_barriers,
+				   notify, callback, name);
+	if (!vq) {
+		dma_free_coherent(vdev->dev.parent,
+				  queue_size_in_bytes, queue,
+				  dma_addr);
+		return NULL;
+	}
+
+	to_vvq(vq)->queue_dma_addr = dma_addr;
+	to_vvq(vq)->queue_size_in_bytes = queue_size_in_bytes;
+	to_vvq(vq)->we_own_ring = true;
+
+	return vq;
+}
+EXPORT_SYMBOL_GPL(vring_create_virtqueue);
+
+struct virtqueue *vring_new_virtqueue(unsigned int index,
+				      unsigned int num,
+				      unsigned int vring_align,
+				      struct virtio_device *vdev,
+				      bool weak_barriers,
+				      void *pages,
+				      bool (*notify)(struct virtqueue *vq),
+				      void (*callback)(struct virtqueue *vq),
+				      const char *name)
+{
+	struct vring vring;
+	vring_init(&vring, num, pages, vring_align);
+	return __vring_new_virtqueue(index, vring, vdev, weak_barriers,
+				     notify, callback, name);
+}
 EXPORT_SYMBOL_GPL(vring_new_virtqueue);
 
-void vring_del_virtqueue(struct virtqueue *vq)
+void vring_del_virtqueue(struct virtqueue *_vq)
 {
-	list_del(&vq->list);
-	kfree(to_vvq(vq));
+	struct vring_virtqueue *vq = to_vvq(_vq);
+
+	if (vq->we_own_ring) {
+		dma_free_coherent(vring_dma_dev(vq), vq->queue_size_in_bytes,
+				  vq->vring.desc, vq->queue_dma_addr);
+	}
+	list_del(&_vq->list);
+	kfree(vq);
 }
 EXPORT_SYMBOL_GPL(vring_del_virtqueue);
 
@@ -946,20 +1033,37 @@ void virtio_break_device(struct virtio_device *dev)
 }
 EXPORT_SYMBOL_GPL(virtio_break_device);
 
-void *virtqueue_get_avail(struct virtqueue *_vq)
+dma_addr_t virtqueue_get_desc_addr(struct virtqueue *_vq)
 {
 	struct vring_virtqueue *vq = to_vvq(_vq);
 
-	return vq->vring.avail;
+	BUG_ON(!vq->we_own_ring);
+	return vq->queue_dma_addr;
 }
-EXPORT_SYMBOL_GPL(virtqueue_get_avail);
+EXPORT_SYMBOL_GPL(virtqueue_get_desc_addr);
 
-void *virtqueue_get_used(struct virtqueue *_vq)
+dma_addr_t virtqueue_get_avail_addr(struct virtqueue *_vq)
 {
 	struct vring_virtqueue *vq = to_vvq(_vq);
 
-	return vq->vring.used;
+	BUG_ON(!vq->we_own_ring);
+	return vq->queue_dma_addr + ((char *)vq->vring.avail - (char *)vq->vring.desc);
+}
+EXPORT_SYMBOL_GPL(virtqueue_get_avail_addr);
+
+dma_addr_t virtqueue_get_used_addr(struct virtqueue *_vq)
+{
+	struct vring_virtqueue *vq = to_vvq(_vq);
+
+	BUG_ON(!vq->we_own_ring);
+	return vq->queue_dma_addr + ((char *)vq->vring.used - (char *)vq->vring.desc);
+}
+EXPORT_SYMBOL_GPL(virtqueue_get_used_addr);
+
+const struct vring *virtqueue_get_vring(struct virtqueue *vq)
+{
+	return &to_vvq(vq)->vring;
 }
-EXPORT_SYMBOL_GPL(virtqueue_get_used);
+EXPORT_SYMBOL_GPL(virtqueue_get_vring);
 
 MODULE_LICENSE("GPL");
diff --git a/include/linux/virtio.h b/include/linux/virtio.h
index 8f4d4bfa6d46..d5eb5479a425 100644
--- a/include/linux/virtio.h
+++ b/include/linux/virtio.h
@@ -75,8 +75,27 @@ unsigned int virtqueue_get_vring_size(struct virtqueue *vq);
 
 bool virtqueue_is_broken(struct virtqueue *vq);
 
-void *virtqueue_get_avail(struct virtqueue *vq);
-void *virtqueue_get_used(struct virtqueue *vq);
+const struct vring *virtqueue_get_vring(struct virtqueue *vq);
+dma_addr_t virtqueue_get_desc_addr(struct virtqueue *vq);
+dma_addr_t virtqueue_get_avail_addr(struct virtqueue *vq);
+dma_addr_t virtqueue_get_used_addr(struct virtqueue *vq);
+
+/*
+ * Legacy accessors -- in almost all cases, these are the wrong functions
+ * to use.
+ */
+static inline void *virtqueue_get_desc(struct virtqueue *vq)
+{
+	return virtqueue_get_vring(vq)->desc;
+}
+static inline void *virtqueue_get_avail(struct virtqueue *vq)
+{
+	return virtqueue_get_vring(vq)->avail;
+}
+static inline void *virtqueue_get_used(struct virtqueue *vq)
+{
+	return virtqueue_get_vring(vq)->used;
+}
 
 /**
  * virtio_device - representation of a device using virtio
diff --git a/include/linux/virtio_ring.h b/include/linux/virtio_ring.h
index 8e50888a6d59..b6b6821917fa 100644
--- a/include/linux/virtio_ring.h
+++ b/include/linux/virtio_ring.h
@@ -50,6 +50,35 @@ static inline void virtio_wmb(bool weak_barriers)
 struct virtio_device;
 struct virtqueue;
 
+/*
+ * Creates a virtqueue and allocates the descriptor ring.  If
+ * may_reduce_num is set, then this may allocate a smaller ring than
+ * expected.  The caller should query virtqueue_get_ring_size to learn
+ * the actual size of the ring.
+ */
+struct virtqueue *vring_create_virtqueue(unsigned int index,
+					 unsigned int num,
+					 unsigned int vring_align,
+					 struct virtio_device *vdev,
+					 bool weak_barriers,
+					 bool may_reduce_num,
+					 bool (*notify)(struct virtqueue *vq),
+					 void (*callback)(struct virtqueue *vq),
+					 const char *name);
+
+/* Creates a virtqueue with a custom layout. */
+struct virtqueue *__vring_new_virtqueue(unsigned int index,
+					struct vring vring,
+					struct virtio_device *vdev,
+					bool weak_barriers,
+					bool (*notify)(struct virtqueue *),
+					void (*callback)(struct virtqueue *),
+					const char *name);
+
+/*
+ * Creates a virtqueue with a standard layout but a caller-allocated
+ * ring.
+ */
 struct virtqueue *vring_new_virtqueue(unsigned int index,
 				      unsigned int num,
 				      unsigned int vring_align,
@@ -59,7 +88,13 @@ struct virtqueue *vring_new_virtqueue(unsigned int index,
 				      bool (*notify)(struct virtqueue *vq),
 				      void (*callback)(struct virtqueue *vq),
 				      const char *name);
+
+/*
+ * Destroys a virtqueue.  If created with vring_create_virtqueue, this
+ * also frees the ring.
+ */
 void vring_del_virtqueue(struct virtqueue *vq);
+
 /* Filter out transport-specific feature bits. */
 void vring_transport_features(struct virtio_device *vdev);
 
-- 
2.4.3

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#1259154 — [PATCH v4 2/6] virtio_ring: Support DMA APIs

FromAndy Lutomirski <luto@kernel.org>
Date2015-10-30 02:20 +0100
Subject[PATCH v4 2/6] virtio_ring: Support DMA APIs
Message-ID<qp6wi-7Kj-21@gated-at.bofh.it>
In reply to#1259147
virtio_ring currently sends the device (usually a hypervisor)
physical addresses of its I/O buffers.  This is okay when DMA
addresses and physical addresses are the same thing, but this isn't
always the case.  For example, this never works on Xen guests, and
it is likely to fail if a physical "virtio" device ever ends up
behind an IOMMU or swiotlb.

The immediate use case for me is to enable virtio on Xen guests.
For that to work, we need vring to support DMA address translation
as well as a corresponding change to virtio_pci or to another
driver.

With this patch, if enabled, virtfs survives kmemleak and
CONFIG_DMA_API_DEBUG.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
 drivers/virtio/Kconfig           |   2 +-
 drivers/virtio/virtio_ring.c     | 190 +++++++++++++++++++++++++++++++--------
 tools/virtio/linux/dma-mapping.h |  17 ++++
 3 files changed, 172 insertions(+), 37 deletions(-)
 create mode 100644 tools/virtio/linux/dma-mapping.h

diff --git a/drivers/virtio/Kconfig b/drivers/virtio/Kconfig
index cab9f3f63a38..77590320d44c 100644
--- a/drivers/virtio/Kconfig
+++ b/drivers/virtio/Kconfig
@@ -60,7 +60,7 @@ config VIRTIO_INPUT
 
  config VIRTIO_MMIO
 	tristate "Platform bus driver for memory mapped virtio devices"
-	depends on HAS_IOMEM
+	depends on HAS_IOMEM && HAS_DMA
  	select VIRTIO
  	---help---
  	 This drivers provides support for memory mapped virtio
diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index 096b857e7b75..a872eb89587f 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -24,6 +24,7 @@
 #include <linux/module.h>
 #include <linux/hrtimer.h>
 #include <linux/kmemleak.h>
+#include <linux/dma-mapping.h>
 
 #ifdef DEBUG
 /* For development, we want to crash whenever the ring is screwed. */
@@ -54,7 +55,14 @@
 #define END_USE(vq)
 #endif
 
-struct vring_virtqueue {
+struct vring_desc_state
+{
+	void *data;			/* Data for callback. */
+	struct vring_desc *indir_desc;	/* Indirect descriptor, if any. */
+};
+
+struct vring_virtqueue
+{
 	struct virtqueue vq;
 
 	/* Actual memory layout for this queue */
@@ -92,12 +100,71 @@ struct vring_virtqueue {
 	ktime_t last_add_time;
 #endif
 
-	/* Tokens for callbacks. */
-	void *data[];
+	/* Per-descriptor state. */
+	struct vring_desc_state desc_state[];
 };
 
 #define to_vvq(_vq) container_of(_vq, struct vring_virtqueue, vq)
 
+/*
+ * The DMA ops on various arches are rather gnarly right now, and
+ * making all of the arch DMA ops work on the vring device itself
+ * is a mess.  For now, we use the parent device for DMA ops.
+ */
+struct device *vring_dma_dev(const struct vring_virtqueue *vq)
+{
+	return vq->vq.vdev->dev.parent;
+}
+
+/* Map one sg entry. */
+static dma_addr_t vring_map_one_sg(const struct vring_virtqueue *vq,
+				   struct scatterlist *sg,
+				   enum dma_data_direction direction)
+{
+	/*
+	 * We can't use dma_map_sg, because we don't use scatterlists in
+	 * the way it expects (we don't guarantee that the scatterlist
+	 * will exist for the lifetime of the mapping).
+	 */
+	return dma_map_page(vring_dma_dev(vq),
+			    sg_page(sg), sg->offset, sg->length,
+			    direction);
+}
+
+static dma_addr_t vring_map_single(const struct vring_virtqueue *vq,
+				   void *cpu_addr, size_t size,
+				   enum dma_data_direction direction)
+{
+	return dma_map_single(vring_dma_dev(vq),
+			      cpu_addr, size, direction);
+}
+
+static void vring_unmap_one(const struct vring_virtqueue *vq,
+			    struct vring_desc *desc)
+{
+	u16 flags = virtio16_to_cpu(vq->vq.vdev, desc->flags);
+
+	if (flags & VRING_DESC_F_INDIRECT) {
+		dma_unmap_single(vring_dma_dev(vq),
+				 virtio64_to_cpu(vq->vq.vdev, desc->addr),
+				 virtio32_to_cpu(vq->vq.vdev, desc->len),
+				 (flags & VRING_DESC_F_WRITE) ?
+				 DMA_FROM_DEVICE : DMA_TO_DEVICE);
+	} else {
+		dma_unmap_page(vring_dma_dev(vq),
+			       virtio64_to_cpu(vq->vq.vdev, desc->addr),
+			       virtio32_to_cpu(vq->vq.vdev, desc->len),
+			       (flags & VRING_DESC_F_WRITE) ?
+			       DMA_FROM_DEVICE : DMA_TO_DEVICE);
+	}
+}
+
+static int vring_mapping_error(const struct vring_virtqueue *vq,
+			       dma_addr_t addr)
+{
+	return dma_mapping_error(vring_dma_dev(vq), addr);
+}
+
 static struct vring_desc *alloc_indirect(struct virtqueue *_vq,
 					 unsigned int total_sg, gfp_t gfp)
 {
@@ -131,7 +198,7 @@ static inline int virtqueue_add(struct virtqueue *_vq,
 	struct vring_virtqueue *vq = to_vvq(_vq);
 	struct scatterlist *sg;
 	struct vring_desc *desc;
-	unsigned int i, n, avail, descs_used, uninitialized_var(prev);
+	unsigned int i, n, avail, descs_used, uninitialized_var(prev), err_idx;
 	int head;
 	bool indirect;
 
@@ -171,21 +238,15 @@ static inline int virtqueue_add(struct virtqueue *_vq,
 
 	if (desc) {
 		/* Use a single buffer which doesn't continue */
-		vq->vring.desc[head].flags = cpu_to_virtio16(_vq->vdev, VRING_DESC_F_INDIRECT);
-		vq->vring.desc[head].addr = cpu_to_virtio64(_vq->vdev, virt_to_phys(desc));
-		/* avoid kmemleak false positive (hidden by virt_to_phys) */
-		kmemleak_ignore(desc);
-		vq->vring.desc[head].len = cpu_to_virtio32(_vq->vdev, total_sg * sizeof(struct vring_desc));
-
+		indirect = true;
 		/* Set up rest to use this indirect table. */
 		i = 0;
 		descs_used = 1;
-		indirect = true;
 	} else {
+		indirect = false;
 		desc = vq->vring.desc;
 		i = head;
 		descs_used = total_sg;
-		indirect = false;
 	}
 
 	if (vq->vq.num_free < descs_used) {
@@ -200,13 +261,14 @@ static inline int virtqueue_add(struct virtqueue *_vq,
 		return -ENOSPC;
 	}
 
-	/* We're about to use some buffers from the free list. */
-	vq->vq.num_free -= descs_used;
-
 	for (n = 0; n < out_sgs; n++) {
 		for (sg = sgs[n]; sg; sg = sg_next(sg)) {
+			dma_addr_t addr = vring_map_one_sg(vq, sg, DMA_TO_DEVICE);
+			if (vring_mapping_error(vq, addr))
+				goto unmap_release;
+
 			desc[i].flags = cpu_to_virtio16(_vq->vdev, VRING_DESC_F_NEXT);
-			desc[i].addr = cpu_to_virtio64(_vq->vdev, sg_phys(sg));
+			desc[i].addr = cpu_to_virtio64(_vq->vdev, addr);
 			desc[i].len = cpu_to_virtio32(_vq->vdev, sg->length);
 			prev = i;
 			i = virtio16_to_cpu(_vq->vdev, desc[i].next);
@@ -214,8 +276,12 @@ static inline int virtqueue_add(struct virtqueue *_vq,
 	}
 	for (; n < (out_sgs + in_sgs); n++) {
 		for (sg = sgs[n]; sg; sg = sg_next(sg)) {
+			dma_addr_t addr = vring_map_one_sg(vq, sg, DMA_FROM_DEVICE);
+			if (vring_mapping_error(vq, addr))
+				goto unmap_release;
+
 			desc[i].flags = cpu_to_virtio16(_vq->vdev, VRING_DESC_F_NEXT | VRING_DESC_F_WRITE);
-			desc[i].addr = cpu_to_virtio64(_vq->vdev, sg_phys(sg));
+			desc[i].addr = cpu_to_virtio64(_vq->vdev, addr);
 			desc[i].len = cpu_to_virtio32(_vq->vdev, sg->length);
 			prev = i;
 			i = virtio16_to_cpu(_vq->vdev, desc[i].next);
@@ -224,14 +290,33 @@ static inline int virtqueue_add(struct virtqueue *_vq,
 	/* Last one doesn't continue. */
 	desc[prev].flags &= cpu_to_virtio16(_vq->vdev, ~VRING_DESC_F_NEXT);
 
+	if (indirect) {
+		/* Now that the indirect table is filled in, map it. */
+		dma_addr_t addr = vring_map_single(
+			vq, desc, total_sg * sizeof(struct vring_desc),
+			DMA_TO_DEVICE);
+		if (vring_mapping_error(vq, addr))
+			goto unmap_release;
+
+		vq->vring.desc[head].flags = cpu_to_virtio16(_vq->vdev, VRING_DESC_F_INDIRECT);
+		vq->vring.desc[head].addr = cpu_to_virtio64(_vq->vdev, addr);
+
+		vq->vring.desc[head].len = cpu_to_virtio32(_vq->vdev, total_sg * sizeof(struct vring_desc));
+	}
+
+	/* We're using some buffers from the free list. */
+	vq->vq.num_free -= descs_used;
+
 	/* Update free pointer */
 	if (indirect)
 		vq->free_head = virtio16_to_cpu(_vq->vdev, vq->vring.desc[head].next);
 	else
 		vq->free_head = i;
 
-	/* Set token. */
-	vq->data[head] = data;
+	/* Store token and indirect buffer state. */
+	vq->desc_state[head].data = data;
+	if (indirect)
+		vq->desc_state[head].indir_desc = desc;
 
 	/* Put entry in available array (but don't update avail->idx until they
 	 * do sync). */
@@ -253,6 +338,24 @@ static inline int virtqueue_add(struct virtqueue *_vq,
 		virtqueue_kick(_vq);
 
 	return 0;
+
+unmap_release:
+	err_idx = i;
+	i = head;
+
+	for (n = 0; n < total_sg; n++) {
+		if (i == err_idx)
+			break;
+		vring_unmap_one(vq, &desc[i]);
+		i = vq->vring.desc[i].next;
+	}
+
+	vq->vq.num_free += total_sg;
+
+	if (indirect)
+		kfree(desc);
+
+	return -EIO;
 }
 
 /**
@@ -423,27 +526,43 @@ EXPORT_SYMBOL_GPL(virtqueue_kick);
 
 static void detach_buf(struct vring_virtqueue *vq, unsigned int head)
 {
-	unsigned int i;
+	unsigned int i, j;
+	u16 nextflag = cpu_to_virtio16(vq->vq.vdev, VRING_DESC_F_NEXT);
 
 	/* Clear data ptr. */
-	vq->data[head] = NULL;
+	vq->desc_state[head].data = NULL;
 
-	/* Put back on free list: find end */
+	/* Put back on free list: unmap first-level descriptors and find end */
 	i = head;
 
-	/* Free the indirect table */
-	if (vq->vring.desc[i].flags & cpu_to_virtio16(vq->vq.vdev, VRING_DESC_F_INDIRECT))
-		kfree(phys_to_virt(virtio64_to_cpu(vq->vq.vdev, vq->vring.desc[i].addr)));
-
-	while (vq->vring.desc[i].flags & cpu_to_virtio16(vq->vq.vdev, VRING_DESC_F_NEXT)) {
+	while (vq->vring.desc[i].flags & nextflag) {
+		vring_unmap_one(vq, &vq->vring.desc[i]);
 		i = virtio16_to_cpu(vq->vq.vdev, vq->vring.desc[i].next);
 		vq->vq.num_free++;
 	}
 
+	vring_unmap_one(vq, &vq->vring.desc[i]);
 	vq->vring.desc[i].next = cpu_to_virtio16(vq->vq.vdev, vq->free_head);
 	vq->free_head = head;
+
 	/* Plus final descriptor */
 	vq->vq.num_free++;
+
+	/* Free the indirect table, if any, now that it's unmapped. */
+	if (vq->desc_state[head].indir_desc) {
+		struct vring_desc *indir_desc = vq->desc_state[head].indir_desc;
+		u32 len = vq->vring.desc[head].len;
+
+		BUG_ON(!(vq->vring.desc[head].flags &
+			 cpu_to_virtio16(vq->vq.vdev, VRING_DESC_F_INDIRECT)));
+		BUG_ON(len == 0 || len % sizeof(struct vring_desc));
+
+		for (j = 0; j < len / sizeof(struct vring_desc); j++)
+			vring_unmap_one(vq, &indir_desc[j]);
+
+		kfree(vq->desc_state[head].indir_desc);
+		vq->desc_state[head].indir_desc = NULL;
+	}
 }
 
 static inline bool more_used(const struct vring_virtqueue *vq)
@@ -498,13 +617,13 @@ void *virtqueue_get_buf(struct virtqueue *_vq, unsigned int *len)
 		BAD_RING(vq, "id %u out of range\n", i);
 		return NULL;
 	}
-	if (unlikely(!vq->data[i])) {
+	if (unlikely(!vq->desc_state[i].data)) {
 		BAD_RING(vq, "id %u is not a head!\n", i);
 		return NULL;
 	}
 
 	/* detach_buf clears data, so grab it now. */
-	ret = vq->data[i];
+	ret = vq->desc_state[i].data;
 	detach_buf(vq, i);
 	vq->last_used_idx++;
 	/* If we expect an interrupt for the next entry, tell host
@@ -665,10 +784,10 @@ void *virtqueue_detach_unused_buf(struct virtqueue *_vq)
 	START_USE(vq);
 
 	for (i = 0; i < vq->vring.num; i++) {
-		if (!vq->data[i])
+		if (!vq->desc_state[i].data)
 			continue;
 		/* detach_buf clears data, so grab it now. */
-		buf = vq->data[i];
+		buf = vq->desc_state[i].data;
 		detach_buf(vq, i);
 		vq->vring.avail->idx = cpu_to_virtio16(_vq->vdev, virtio16_to_cpu(_vq->vdev, vq->vring.avail->idx) - 1);
 		END_USE(vq);
@@ -721,7 +840,8 @@ struct virtqueue *vring_new_virtqueue(unsigned int index,
 		return NULL;
 	}
 
-	vq = kmalloc(sizeof(*vq) + sizeof(void *)*num, GFP_KERNEL);
+	vq = kmalloc(sizeof(*vq) + num * sizeof(struct vring_desc_state),
+		     GFP_KERNEL);
 	if (!vq)
 		return NULL;
 
@@ -751,11 +871,9 @@ struct virtqueue *vring_new_virtqueue(unsigned int index,
 
 	/* Put everything in free lists. */
 	vq->free_head = 0;
-	for (i = 0; i < num-1; i++) {
+	for (i = 0; i < num-1; i++)
 		vq->vring.desc[i].next = cpu_to_virtio16(vdev, i + 1);
-		vq->data[i] = NULL;
-	}
-	vq->data[i] = NULL;
+	memset(vq->desc_state, 0, num * sizeof(struct vring_desc_state));
 
 	return &vq->vq;
 }
diff --git a/tools/virtio/linux/dma-mapping.h b/tools/virtio/linux/dma-mapping.h
new file mode 100644
index 000000000000..4f93af89ae16
--- /dev/null
+++ b/tools/virtio/linux/dma-mapping.h
@@ -0,0 +1,17 @@
+#ifndef _LINUX_DMA_MAPPING_H
+#define _LINUX_DMA_MAPPING_H
+
+#ifdef CONFIG_HAS_DMA
+# error Virtio userspace code does not support CONFIG_HAS_DMA
+#endif
+
+#define PCI_DMA_BUS_IS_PHYS 1
+
+enum dma_data_direction {
+	DMA_BIDIRECTIONAL = 0,
+	DMA_TO_DEVICE = 1,
+	DMA_FROM_DEVICE = 2,
+	DMA_NONE = 3,
+};
+
+#endif
-- 
2.4.3

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#1259442 — Re: [PATCH v4 2/6] virtio_ring: Support DMA APIs

FromCornelia Huck <cornelia.huck@de.ibm.com>
Date2015-10-30 13:10 +0100
SubjectRe: [PATCH v4 2/6] virtio_ring: Support DMA APIs
Message-ID<qpgFj-5Eg-5@gated-at.bofh.it>
In reply to#1259154
On Thu, 29 Oct 2015 18:09:47 -0700
Andy Lutomirski <luto@kernel.org> wrote:

> virtio_ring currently sends the device (usually a hypervisor)
> physical addresses of its I/O buffers.  This is okay when DMA
> addresses and physical addresses are the same thing, but this isn't
> always the case.  For example, this never works on Xen guests, and
> it is likely to fail if a physical "virtio" device ever ends up
> behind an IOMMU or swiotlb.
> 
> The immediate use case for me is to enable virtio on Xen guests.
> For that to work, we need vring to support DMA address translation
> as well as a corresponding change to virtio_pci or to another
> driver.
> 
> With this patch, if enabled, virtfs survives kmemleak and
> CONFIG_DMA_API_DEBUG.
> 
> Signed-off-by: Andy Lutomirski <luto@kernel.org>
> ---
>  drivers/virtio/Kconfig           |   2 +-
>  drivers/virtio/virtio_ring.c     | 190 +++++++++++++++++++++++++++++++--------
>  tools/virtio/linux/dma-mapping.h |  17 ++++
>  3 files changed, 172 insertions(+), 37 deletions(-)
>  create mode 100644 tools/virtio/linux/dma-mapping.h

>  static void detach_buf(struct vring_virtqueue *vq, unsigned int head)
>  {
> -	unsigned int i;
> +	unsigned int i, j;
> +	u16 nextflag = cpu_to_virtio16(vq->vq.vdev, VRING_DESC_F_NEXT);
> 
>  	/* Clear data ptr. */
> -	vq->data[head] = NULL;
> +	vq->desc_state[head].data = NULL;
> 
> -	/* Put back on free list: find end */
> +	/* Put back on free list: unmap first-level descriptors and find end */
>  	i = head;
> 
> -	/* Free the indirect table */
> -	if (vq->vring.desc[i].flags & cpu_to_virtio16(vq->vq.vdev, VRING_DESC_F_INDIRECT))
> -		kfree(phys_to_virt(virtio64_to_cpu(vq->vq.vdev, vq->vring.desc[i].addr)));
> -
> -	while (vq->vring.desc[i].flags & cpu_to_virtio16(vq->vq.vdev, VRING_DESC_F_NEXT)) {
> +	while (vq->vring.desc[i].flags & nextflag) {
> +		vring_unmap_one(vq, &vq->vring.desc[i]);
>  		i = virtio16_to_cpu(vq->vq.vdev, vq->vring.desc[i].next);
>  		vq->vq.num_free++;
>  	}
> 
> +	vring_unmap_one(vq, &vq->vring.desc[i]);
>  	vq->vring.desc[i].next = cpu_to_virtio16(vq->vq.vdev, vq->free_head);
>  	vq->free_head = head;
> +
>  	/* Plus final descriptor */
>  	vq->vq.num_free++;
> +
> +	/* Free the indirect table, if any, now that it's unmapped. */
> +	if (vq->desc_state[head].indir_desc) {
> +		struct vring_desc *indir_desc = vq->desc_state[head].indir_desc;
> +		u32 len = vq->vring.desc[head].len;

This one needs to be virtio32_to_cpu(...) as well.

> +
> +		BUG_ON(!(vq->vring.desc[head].flags &
> +			 cpu_to_virtio16(vq->vq.vdev, VRING_DESC_F_INDIRECT)));
> +		BUG_ON(len == 0 || len % sizeof(struct vring_desc));
> +
> +		for (j = 0; j < len / sizeof(struct vring_desc); j++)
> +			vring_unmap_one(vq, &indir_desc[j]);
> +
> +		kfree(vq->desc_state[head].indir_desc);
> +		vq->desc_state[head].indir_desc = NULL;
> +	}
>  }

With that change on top of your current branch, I can boot (root on
virtio-blk, either virtio-1 or legacy virtio) on current qemu master
with kvm enabled on s390. Haven't tried anything further.

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#1259453 — Re: [PATCH v4 2/6] virtio_ring: Support DMA APIs

FromChristian Borntraeger <borntraeger@de.ibm.com>
Date2015-10-30 13:10 +0100
SubjectRe: [PATCH v4 2/6] virtio_ring: Support DMA APIs
Message-ID<qpgFk-5Eg-31@gated-at.bofh.it>
In reply to#1259442
Am 30.10.2015 um 13:01 schrieb Cornelia Huck:
> On Thu, 29 Oct 2015 18:09:47 -0700
> Andy Lutomirski <luto@kernel.org> wrote:
> 
>> virtio_ring currently sends the device (usually a hypervisor)
>> physical addresses of its I/O buffers.  This is okay when DMA
>> addresses and physical addresses are the same thing, but this isn't
>> always the case.  For example, this never works on Xen guests, and
>> it is likely to fail if a physical "virtio" device ever ends up
>> behind an IOMMU or swiotlb.
>>
>> The immediate use case for me is to enable virtio on Xen guests.
>> For that to work, we need vring to support DMA address translation
>> as well as a corresponding change to virtio_pci or to another
>> driver.
>>
>> With this patch, if enabled, virtfs survives kmemleak and
>> CONFIG_DMA_API_DEBUG.
>>
>> Signed-off-by: Andy Lutomirski <luto@kernel.org>
>> ---
>>  drivers/virtio/Kconfig           |   2 +-
>>  drivers/virtio/virtio_ring.c     | 190 +++++++++++++++++++++++++++++++--------
>>  tools/virtio/linux/dma-mapping.h |  17 ++++
>>  3 files changed, 172 insertions(+), 37 deletions(-)
>>  create mode 100644 tools/virtio/linux/dma-mapping.h
> 
>>  static void detach_buf(struct vring_virtqueue *vq, unsigned int head)
>>  {
>> -	unsigned int i;
>> +	unsigned int i, j;
>> +	u16 nextflag = cpu_to_virtio16(vq->vq.vdev, VRING_DESC_F_NEXT);
>>
>>  	/* Clear data ptr. */
>> -	vq->data[head] = NULL;
>> +	vq->desc_state[head].data = NULL;
>>
>> -	/* Put back on free list: find end */
>> +	/* Put back on free list: unmap first-level descriptors and find end */
>>  	i = head;
>>
>> -	/* Free the indirect table */
>> -	if (vq->vring.desc[i].flags & cpu_to_virtio16(vq->vq.vdev, VRING_DESC_F_INDIRECT))
>> -		kfree(phys_to_virt(virtio64_to_cpu(vq->vq.vdev, vq->vring.desc[i].addr)));
>> -
>> -	while (vq->vring.desc[i].flags & cpu_to_virtio16(vq->vq.vdev, VRING_DESC_F_NEXT)) {
>> +	while (vq->vring.desc[i].flags & nextflag) {
>> +		vring_unmap_one(vq, &vq->vring.desc[i]);
>>  		i = virtio16_to_cpu(vq->vq.vdev, vq->vring.desc[i].next);
>>  		vq->vq.num_free++;
>>  	}
>>
>> +	vring_unmap_one(vq, &vq->vring.desc[i]);
>>  	vq->vring.desc[i].next = cpu_to_virtio16(vq->vq.vdev, vq->free_head);
>>  	vq->free_head = head;
>> +
>>  	/* Plus final descriptor */
>>  	vq->vq.num_free++;
>> +
>> +	/* Free the indirect table, if any, now that it's unmapped. */
>> +	if (vq->desc_state[head].indir_desc) {
>> +		struct vring_desc *indir_desc = vq->desc_state[head].indir_desc;
>> +		u32 len = vq->vring.desc[head].len;
> 
> This one needs to be virtio32_to_cpu(...) as well.

Yes, just did the exact same change
diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index f269e1c..f2249df 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -556,7 +556,7 @@ static void detach_buf(struct vring_virtqueue *vq, unsigned int head)
        /* Free the indirect table, if any, now that it's unmapped. */
        if (vq->desc_state[head].indir_desc) {
                struct vring_desc *indir_desc = vq->desc_state[head].indir_desc;
-               u32 len = vq->vring.desc[head].len;
+               u32 len = virtio32_to_cpu(vq->vq.vdev, vq->vring.desc[head].len);
 
                BUG_ON(!(vq->vring.desc[head].flags &
                         cpu_to_virtio16(vq->vq.vdev, VRING_DESC_F_INDIRECT)));


now it boots.
> 
>> +
>> +		BUG_ON(!(vq->vring.desc[head].flags &
>> +			 cpu_to_virtio16(vq->vq.vdev, VRING_DESC_F_INDIRECT)));
>> +		BUG_ON(len == 0 || len % sizeof(struct vring_desc));
>> +
>> +		for (j = 0; j < len / sizeof(struct vring_desc); j++)
>> +			vring_unmap_one(vq, &indir_desc[j]);
>> +
>> +		kfree(vq->desc_state[head].indir_desc);
>> +		vq->desc_state[head].indir_desc = NULL;
>> +	}
>>  }
> 
> With that change on top of your current branch, I can boot (root on
> virtio-blk, either virtio-1 or legacy virtio) on current qemu master
> with kvm enabled on s390. Haven't tried anything further.
> 

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#1259720 — Re: [PATCH v4 2/6] virtio_ring: Support DMA APIs

FromAndy Lutomirski <luto@amacapital.net>
Date2015-10-30 20:00 +0100
SubjectRe: [PATCH v4 2/6] virtio_ring: Support DMA APIs
Message-ID<qpn46-WF-21@gated-at.bofh.it>
In reply to#1259453
On Fri, Oct 30, 2015 at 5:05 AM, Christian Borntraeger
<borntraeger@de.ibm.com> wrote:
> Am 30.10.2015 um 13:01 schrieb Cornelia Huck:
>> On Thu, 29 Oct 2015 18:09:47 -0700
>> Andy Lutomirski <luto@kernel.org> wrote:
>>
>>> virtio_ring currently sends the device (usually a hypervisor)
>>> physical addresses of its I/O buffers.  This is okay when DMA
>>> addresses and physical addresses are the same thing, but this isn't
>>> always the case.  For example, this never works on Xen guests, and
>>> it is likely to fail if a physical "virtio" device ever ends up
>>> behind an IOMMU or swiotlb.
>>>
>>> The immediate use case for me is to enable virtio on Xen guests.
>>> For that to work, we need vring to support DMA address translation
>>> as well as a corresponding change to virtio_pci or to another
>>> driver.
>>>
>>> With this patch, if enabled, virtfs survives kmemleak and
>>> CONFIG_DMA_API_DEBUG.
>>>
>>> Signed-off-by: Andy Lutomirski <luto@kernel.org>
>>> ---
>>>  drivers/virtio/Kconfig           |   2 +-
>>>  drivers/virtio/virtio_ring.c     | 190 +++++++++++++++++++++++++++++++--------
>>>  tools/virtio/linux/dma-mapping.h |  17 ++++
>>>  3 files changed, 172 insertions(+), 37 deletions(-)
>>>  create mode 100644 tools/virtio/linux/dma-mapping.h
>>
>>>  static void detach_buf(struct vring_virtqueue *vq, unsigned int head)
>>>  {
>>> -    unsigned int i;
>>> +    unsigned int i, j;
>>> +    u16 nextflag = cpu_to_virtio16(vq->vq.vdev, VRING_DESC_F_NEXT);
>>>
>>>      /* Clear data ptr. */
>>> -    vq->data[head] = NULL;
>>> +    vq->desc_state[head].data = NULL;
>>>
>>> -    /* Put back on free list: find end */
>>> +    /* Put back on free list: unmap first-level descriptors and find end */
>>>      i = head;
>>>
>>> -    /* Free the indirect table */
>>> -    if (vq->vring.desc[i].flags & cpu_to_virtio16(vq->vq.vdev, VRING_DESC_F_INDIRECT))
>>> -            kfree(phys_to_virt(virtio64_to_cpu(vq->vq.vdev, vq->vring.desc[i].addr)));
>>> -
>>> -    while (vq->vring.desc[i].flags & cpu_to_virtio16(vq->vq.vdev, VRING_DESC_F_NEXT)) {
>>> +    while (vq->vring.desc[i].flags & nextflag) {
>>> +            vring_unmap_one(vq, &vq->vring.desc[i]);
>>>              i = virtio16_to_cpu(vq->vq.vdev, vq->vring.desc[i].next);
>>>              vq->vq.num_free++;
>>>      }
>>>
>>> +    vring_unmap_one(vq, &vq->vring.desc[i]);
>>>      vq->vring.desc[i].next = cpu_to_virtio16(vq->vq.vdev, vq->free_head);
>>>      vq->free_head = head;
>>> +
>>>      /* Plus final descriptor */
>>>      vq->vq.num_free++;
>>> +
>>> +    /* Free the indirect table, if any, now that it's unmapped. */
>>> +    if (vq->desc_state[head].indir_desc) {
>>> +            struct vring_desc *indir_desc = vq->desc_state[head].indir_desc;
>>> +            u32 len = vq->vring.desc[head].len;
>>
>> This one needs to be virtio32_to_cpu(...) as well.
>
> Yes, just did the exact same change
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index f269e1c..f2249df 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -556,7 +556,7 @@ static void detach_buf(struct vring_virtqueue *vq, unsigned int head)
>         /* Free the indirect table, if any, now that it's unmapped. */
>         if (vq->desc_state[head].indir_desc) {
>                 struct vring_desc *indir_desc = vq->desc_state[head].indir_desc;
> -               u32 len = vq->vring.desc[head].len;
> +               u32 len = virtio32_to_cpu(vq->vq.vdev, vq->vring.desc[head].len);
>
>                 BUG_ON(!(vq->vring.desc[head].flags &
>                          cpu_to_virtio16(vq->vq.vdev, VRING_DESC_F_INDIRECT)));
>
>
> now it boots.

Thanks!  I applied this to my tree.  I won't send a new version quite
yet, though, to reduce inbox load.

--Andy
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#1259366

FromChristian Borntraeger <borntraeger@de.ibm.com>
Date2015-10-30 11:00 +0100
Message-ID<qpeDw-4cd-3@gated-at.bofh.it>
In reply to#1259147
Am 30.10.2015 um 02:09 schrieb Andy Lutomirski:
> This switches virtio to use the DMA API unconditionally.  I'm sure
> it breaks things, but it seems to work on x86 using virtio-pci, with
> and without Xen, and using both the modern 1.0 variant and the
> legacy variant.
> 
> This appears to work on native and Xen x86_64 using both modern and
> legacy virtio-pci.  It also appears to work on arm and arm64.
> 
> It definitely won't work as-is on s390x, and I haven't been able to
> test Christian's patches because I can't get virtio-ccw to work in
> QEMU at all.  I don't know what I'm doing wrong.


[...]
>   virtio-net: Stop doing DMA from the stack
> 
>  drivers/net/virtio_net.c           |  34 ++--
>  drivers/virtio/Kconfig             |   2 +-
>  drivers/virtio/virtio_mmio.c       |  67 ++-----
>  drivers/virtio/virtio_pci_common.h |   6 -
>  drivers/virtio/virtio_pci_legacy.c |  42 ++---
>  drivers/virtio/virtio_pci_modern.c |  61 ++-----
>  drivers/virtio/virtio_ring.c       | 348 ++++++++++++++++++++++++++++++-------

do you also have an untested patch for drivers/s390/virtio/* ?



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