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[PATCH v2 0/3] virtio DMA API core stuff

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  [PATCH v2 0/3] virtio DMA API core stuff Andy Lutomirski <luto@kernel.org> - 2015-10-28 06:40 +0100
    [PATCH v2 1/3] virtio_net: Stop doing DMA from the stack Andy Lutomirski <luto@kernel.org> - 2015-10-28 06:40 +0100
      Re: [PATCH v2 1/3] virtio_net: Stop doing DMA from the stack "Michael S. Tsirkin" <mst@redhat.com> - 2015-10-28 08:10 +0100
        Re: [PATCH v2 1/3] virtio_net: Stop doing DMA from the stack Andy Lutomirski <luto@amacapital.net> - 2015-10-30 00:50 +0100
    [PATCH v2 2/3] virtio_ring: Support DMA APIs Andy Lutomirski <luto@kernel.org> - 2015-10-28 06:40 +0100
      Re: [PATCH v2 2/3] virtio_ring: Support DMA APIs Christian Borntraeger <borntraeger@de.ibm.com> - 2015-10-28 07:00 +0100
        Re: [PATCH v2 2/3] virtio_ring: Support DMA APIs David Woodhouse <dwmw2@infradead.org> - 2015-10-28 07:10 +0100
          Re: [PATCH v2 2/3] virtio_ring: Support DMA APIs Christian Borntraeger <borntraeger@de.ibm.com> - 2015-10-28 09:50 +0100

#1257673 — [PATCH v2 0/3] virtio DMA API core stuff

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.

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 (3):
  virtio_net: Stop doing DMA from the stack
  virtio_ring: Support DMA APIs
  virtio_pci: Use the DMA API

 drivers/net/virtio_net.c           |  53 +++++++----
 drivers/virtio/Kconfig             |   2 +-
 drivers/virtio/virtio_pci_common.h |   3 +-
 drivers/virtio/virtio_pci_legacy.c |  19 +++-
 drivers/virtio/virtio_pci_modern.c |  34 +++++--
 drivers/virtio/virtio_ring.c       | 187 ++++++++++++++++++++++++++++++-------
 tools/virtio/linux/dma-mapping.h   |  17 ++++
 7 files changed, 246 insertions(+), 69 deletions(-)
 create mode 100644 tools/virtio/linux/dma-mapping.h

-- 
2.4.3

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#1257674 — [PATCH v2 1/3] virtio_net: Stop doing DMA from the stack

From: Andy Lutomirski <luto@amacapital.net>

Once virtio starts using the DMA API, we won't be able to safely DMA
from the stack.  virtio-net does a couple of config DMA requests
from small stack buffers -- switch to using dynamically-allocated
memory.

This should have no effect on any performance-critical code paths.

Cc: netdev@vger.kernel.org
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: virtualization@lists.linux-foundation.org
Reviewed-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Andy Lutomirski <luto@kernel.org>
---

Hi Michael and DaveM-

This is a prerequisite for the virtio DMA fixing project.  It works
as a standalone patch, though.  Would it make sense to apply it to
an appropriate networking tree now?

 drivers/net/virtio_net.c | 53 ++++++++++++++++++++++++++++++++----------------
 1 file changed, 36 insertions(+), 17 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index d8838dedb7a4..4f10f8a58811 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -976,31 +976,43 @@ static bool virtnet_send_command(struct virtnet_info *vi, u8 class, u8 cmd,
 				 struct scatterlist *out)
 {
 	struct scatterlist *sgs[4], hdr, stat;
-	struct virtio_net_ctrl_hdr ctrl;
-	virtio_net_ctrl_ack status = ~0;
+
+	struct {
+		struct virtio_net_ctrl_hdr ctrl;
+		virtio_net_ctrl_ack status;
+	} *buf;
+
 	unsigned out_num = 0, tmp;
+	bool ret;
 
 	/* Caller should know better */
 	BUG_ON(!virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_VQ));
 
-	ctrl.class = class;
-	ctrl.cmd = cmd;
+	buf = kmalloc(sizeof(*buf), GFP_ATOMIC);
+	if (!buf)
+		return false;
+	buf->status = ~0;
+
+	buf->ctrl.class = class;
+	buf->ctrl.cmd = cmd;
 	/* Add header */
-	sg_init_one(&hdr, &ctrl, sizeof(ctrl));
+	sg_init_one(&hdr, &buf->ctrl, sizeof(buf->ctrl));
 	sgs[out_num++] = &hdr;
 
 	if (out)
 		sgs[out_num++] = out;
 
 	/* Add return status. */
-	sg_init_one(&stat, &status, sizeof(status));
+	sg_init_one(&stat, &buf->status, sizeof(buf->status));
 	sgs[out_num] = &stat;
 
 	BUG_ON(out_num + 1 > ARRAY_SIZE(sgs));
 	virtqueue_add_sgs(vi->cvq, sgs, out_num, 1, vi, GFP_ATOMIC);
 
-	if (unlikely(!virtqueue_kick(vi->cvq)))
-		return status == VIRTIO_NET_OK;
+	if (unlikely(!virtqueue_kick(vi->cvq))) {
+		ret = (buf->status == VIRTIO_NET_OK);
+		goto out;
+	}
 
 	/* Spin for a response, the kick causes an ioport write, trapping
 	 * into the hypervisor, so the request should be handled immediately.
@@ -1009,7 +1021,11 @@ static bool virtnet_send_command(struct virtnet_info *vi, u8 class, u8 cmd,
 	       !virtqueue_is_broken(vi->cvq))
 		cpu_relax();
 
-	return status == VIRTIO_NET_OK;
+	ret = (buf->status == VIRTIO_NET_OK);
+
+out:
+	kfree(buf);
+	return ret;
 }
 
 static int virtnet_set_mac_address(struct net_device *dev, void *p)
@@ -1151,7 +1167,7 @@ static void virtnet_set_rx_mode(struct net_device *dev)
 {
 	struct virtnet_info *vi = netdev_priv(dev);
 	struct scatterlist sg[2];
-	u8 promisc, allmulti;
+	u8 *cmdbyte;
 	struct virtio_net_ctrl_mac *mac_data;
 	struct netdev_hw_addr *ha;
 	int uc_count;
@@ -1163,22 +1179,25 @@ static void virtnet_set_rx_mode(struct net_device *dev)
 	if (!virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_RX))
 		return;
 
-	promisc = ((dev->flags & IFF_PROMISC) != 0);
-	allmulti = ((dev->flags & IFF_ALLMULTI) != 0);
+	cmdbyte = kmalloc(sizeof(*cmdbyte), GFP_ATOMIC);
+	if (!cmdbyte)
+		return;
 
-	sg_init_one(sg, &promisc, sizeof(promisc));
+	sg_init_one(sg, cmdbyte, sizeof(*cmdbyte));
 
+	*cmdbyte = ((dev->flags & IFF_PROMISC) != 0);
 	if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_RX,
 				  VIRTIO_NET_CTRL_RX_PROMISC, sg))
 		dev_warn(&dev->dev, "Failed to %sable promisc mode.\n",
-			 promisc ? "en" : "dis");
-
-	sg_init_one(sg, &allmulti, sizeof(allmulti));
+			 *cmdbyte ? "en" : "dis");
 
+	*cmdbyte = ((dev->flags & IFF_ALLMULTI) != 0);
 	if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_RX,
 				  VIRTIO_NET_CTRL_RX_ALLMULTI, sg))
 		dev_warn(&dev->dev, "Failed to %sable allmulti mode.\n",
-			 allmulti ? "en" : "dis");
+			 *cmdbyte ? "en" : "dis");
+
+	kfree(cmdbyte);
 
 	uc_count = netdev_uc_count(dev);
 	mc_count = netdev_mc_count(dev);
-- 
2.4.3

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#1257727 — Re: [PATCH v2 1/3] virtio_net: Stop doing DMA from the stack

On Tue, Oct 27, 2015 at 10:30:19PM -0700, Andy Lutomirski wrote:
> From: Andy Lutomirski <luto@amacapital.net>
> 
> Once virtio starts using the DMA API, we won't be able to safely DMA
> from the stack.  virtio-net does a couple of config DMA requests
> from small stack buffers -- switch to using dynamically-allocated
> memory.
> 
> This should have no effect on any performance-critical code paths.
> 
> Cc: netdev@vger.kernel.org
> Cc: "Michael S. Tsirkin" <mst@redhat.com>
> Cc: virtualization@lists.linux-foundation.org
> Reviewed-by: Joerg Roedel <jroedel@suse.de>
> Signed-off-by: Andy Lutomirski <luto@kernel.org>
> ---
> 
> Hi Michael and DaveM-
> 
> This is a prerequisite for the virtio DMA fixing project.  It works
> as a standalone patch, though.  Would it make sense to apply it to
> an appropriate networking tree now?
> 
>  drivers/net/virtio_net.c | 53 ++++++++++++++++++++++++++++++++----------------
>  1 file changed, 36 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index d8838dedb7a4..4f10f8a58811 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -976,31 +976,43 @@ static bool virtnet_send_command(struct virtnet_info *vi, u8 class, u8 cmd,
>  				 struct scatterlist *out)
>  {
>  	struct scatterlist *sgs[4], hdr, stat;
> -	struct virtio_net_ctrl_hdr ctrl;
> -	virtio_net_ctrl_ack status = ~0;
> +
> +	struct {
> +		struct virtio_net_ctrl_hdr ctrl;
> +		virtio_net_ctrl_ack status;
> +	} *buf;
> +
>  	unsigned out_num = 0, tmp;
> +	bool ret;
>  
>  	/* Caller should know better */
>  	BUG_ON(!virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_VQ));
>  
> -	ctrl.class = class;
> -	ctrl.cmd = cmd;
> +	buf = kmalloc(sizeof(*buf), GFP_ATOMIC);
> +	if (!buf)
> +		return false;

This is problematic. The command is never retried, the error
is propagated to userspace.

> +	buf->status = ~0;
> +
> +	buf->ctrl.class = class;
> +	buf->ctrl.cmd = cmd;
>  	/* Add header */
> -	sg_init_one(&hdr, &ctrl, sizeof(ctrl));
> +	sg_init_one(&hdr, &buf->ctrl, sizeof(buf->ctrl));
>  	sgs[out_num++] = &hdr;
>  
>  	if (out)
>  		sgs[out_num++] = out;
>  
>  	/* Add return status. */
> -	sg_init_one(&stat, &status, sizeof(status));
> +	sg_init_one(&stat, &buf->status, sizeof(buf->status));
>  	sgs[out_num] = &stat;
>  
>  	BUG_ON(out_num + 1 > ARRAY_SIZE(sgs));
>  	virtqueue_add_sgs(vi->cvq, sgs, out_num, 1, vi, GFP_ATOMIC);
>  
> -	if (unlikely(!virtqueue_kick(vi->cvq)))
> -		return status == VIRTIO_NET_OK;
> +	if (unlikely(!virtqueue_kick(vi->cvq))) {
> +		ret = (buf->status == VIRTIO_NET_OK);
> +		goto out;
> +	}
>  
>  	/* Spin for a response, the kick causes an ioport write, trapping
>  	 * into the hypervisor, so the request should be handled immediately.
> @@ -1009,7 +1021,11 @@ static bool virtnet_send_command(struct virtnet_info *vi, u8 class, u8 cmd,
>  	       !virtqueue_is_broken(vi->cvq))
>  		cpu_relax();
>  
> -	return status == VIRTIO_NET_OK;
> +	ret = (buf->status == VIRTIO_NET_OK);
> +
> +out:
> +	kfree(buf);
> +	return ret;
>  }
>  
>  static int virtnet_set_mac_address(struct net_device *dev, void *p)
> @@ -1151,7 +1167,7 @@ static void virtnet_set_rx_mode(struct net_device *dev)
>  {
>  	struct virtnet_info *vi = netdev_priv(dev);
>  	struct scatterlist sg[2];
> -	u8 promisc, allmulti;
> +	u8 *cmdbyte;
>  	struct virtio_net_ctrl_mac *mac_data;
>  	struct netdev_hw_addr *ha;
>  	int uc_count;
> @@ -1163,22 +1179,25 @@ static void virtnet_set_rx_mode(struct net_device *dev)
>  	if (!virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_RX))
>  		return;
>  
> -	promisc = ((dev->flags & IFF_PROMISC) != 0);
> -	allmulti = ((dev->flags & IFF_ALLMULTI) != 0);
> +	cmdbyte = kmalloc(sizeof(*cmdbyte), GFP_ATOMIC);
> +	if (!cmdbyte)
> +		return;

Here the error is ignored, rx mode will be incorrect.
OTOH it looks like that's already the case.

>  
> -	sg_init_one(sg, &promisc, sizeof(promisc));
> +	sg_init_one(sg, cmdbyte, sizeof(*cmdbyte));
>  
> +	*cmdbyte = ((dev->flags & IFF_PROMISC) != 0);
>  	if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_RX,
>  				  VIRTIO_NET_CTRL_RX_PROMISC, sg))
>  		dev_warn(&dev->dev, "Failed to %sable promisc mode.\n",
> -			 promisc ? "en" : "dis");
> -
> -	sg_init_one(sg, &allmulti, sizeof(allmulti));
> +			 *cmdbyte ? "en" : "dis");
>  
> +	*cmdbyte = ((dev->flags & IFF_ALLMULTI) != 0);
>  	if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_RX,
>  				  VIRTIO_NET_CTRL_RX_ALLMULTI, sg))
>  		dev_warn(&dev->dev, "Failed to %sable allmulti mode.\n",
> -			 allmulti ? "en" : "dis");
> +			 *cmdbyte ? "en" : "dis");
> +
> +	kfree(cmdbyte);
>  
>  	uc_count = netdev_uc_count(dev);
>  	mc_count = netdev_mc_count(dev);

How about this instead? Less code, more robust.

Warning: untested.  If you do like this approach, Tested-by would be
appreciated.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

---

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index d8838ded..f94ab78 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -140,6 +140,12 @@ struct virtnet_info {
 
 	/* CPU hot plug notifier */
 	struct notifier_block nb;
+
+	/* Control VQ buffers: protected by the rtnl lock */
+	struct virtio_net_ctrl_hdr ctrl_hdr;
+	virtio_net_ctrl_ack ctrl_status;
+	u8 ctrl_promisc;
+	u8 ctrl_allmulti;
 };
 
 struct padded_vnet_hdr {
@@ -976,31 +982,30 @@ static bool virtnet_send_command(struct virtnet_info *vi, u8 class, u8 cmd,
 				 struct scatterlist *out)
 {
 	struct scatterlist *sgs[4], hdr, stat;
-	struct virtio_net_ctrl_hdr ctrl;
-	virtio_net_ctrl_ack status = ~0;
 	unsigned out_num = 0, tmp;
 
 	/* Caller should know better */
 	BUG_ON(!virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_VQ));
 
-	ctrl.class = class;
-	ctrl.cmd = cmd;
+	vi->ctrl_status = ~0;
+	vi->ctrl_hdr.class = class;
+	vi->ctrl_hdr.cmd = cmd;
 	/* Add header */
-	sg_init_one(&hdr, &ctrl, sizeof(ctrl));
+	sg_init_one(&hdr, &vi->ctrl_hdr, sizeof(vi->ctrl_hdr));
 	sgs[out_num++] = &hdr;
 
 	if (out)
 		sgs[out_num++] = out;
 
 	/* Add return status. */
-	sg_init_one(&stat, &status, sizeof(status));
+	sg_init_one(&stat, &vi->ctrl_status, sizeof(vi->ctrl_status));
 	sgs[out_num] = &stat;
 
 	BUG_ON(out_num + 1 > ARRAY_SIZE(sgs));
 	virtqueue_add_sgs(vi->cvq, sgs, out_num, 1, vi, GFP_ATOMIC);
 
 	if (unlikely(!virtqueue_kick(vi->cvq)))
-		return status == VIRTIO_NET_OK;
+		return vi->ctrl_status == VIRTIO_NET_OK;
 
 	/* Spin for a response, the kick causes an ioport write, trapping
 	 * into the hypervisor, so the request should be handled immediately.
@@ -1009,7 +1014,7 @@ static bool virtnet_send_command(struct virtnet_info *vi, u8 class, u8 cmd,
 	       !virtqueue_is_broken(vi->cvq))
 		cpu_relax();
 
-	return status == VIRTIO_NET_OK;
+	return vi->ctrl_status == VIRTIO_NET_OK;
 }
 
 static int virtnet_set_mac_address(struct net_device *dev, void *p)
@@ -1151,7 +1156,6 @@ static void virtnet_set_rx_mode(struct net_device *dev)
 {
 	struct virtnet_info *vi = netdev_priv(dev);
 	struct scatterlist sg[2];
-	u8 promisc, allmulti;
 	struct virtio_net_ctrl_mac *mac_data;
 	struct netdev_hw_addr *ha;
 	int uc_count;
@@ -1163,22 +1167,22 @@ static void virtnet_set_rx_mode(struct net_device *dev)
 	if (!virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_RX))
 		return;
 
-	promisc = ((dev->flags & IFF_PROMISC) != 0);
-	allmulti = ((dev->flags & IFF_ALLMULTI) != 0);
+	vi->ctrl_promisc = ((dev->flags & IFF_PROMISC) != 0);
+	vi->ctrl_allmulti = ((dev->flags & IFF_ALLMULTI) != 0);
 
-	sg_init_one(sg, &promisc, sizeof(promisc));
+	sg_init_one(sg, &vi->ctrl_promisc, sizeof(vi->ctrl_promisc));
 
 	if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_RX,
 				  VIRTIO_NET_CTRL_RX_PROMISC, sg))
 		dev_warn(&dev->dev, "Failed to %sable promisc mode.\n",
-			 promisc ? "en" : "dis");
+			 vi->ctrl_promisc ? "en" : "dis");
 
-	sg_init_one(sg, &allmulti, sizeof(allmulti));
+	sg_init_one(sg, &vi->ctrl_allmulti, sizeof(vi->ctrl_allmulti));
 
 	if (!virtnet_send_command(vi, VIRTIO_NET_CTRL_RX,
 				  VIRTIO_NET_CTRL_RX_ALLMULTI, sg))
 		dev_warn(&dev->dev, "Failed to %sable allmulti mode.\n",
-			 allmulti ? "en" : "dis");
+			 vi->ctrl_allmulti ? "en" : "dis");
 
 	uc_count = netdev_uc_count(dev);
 	mc_count = netdev_mc_count(dev);
> -- 
> 2.4.3
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#1259127 — Re: [PATCH v2 1/3] virtio_net: Stop doing DMA from the stack

On Wed, Oct 28, 2015 at 12:07 AM, Michael S. Tsirkin <mst@redhat.com> wrote:
> How about this instead? Less code, more robust.
>
> Warning: untested.  If you do like this approach, Tested-by would be
> appreciated.

I like it.

Tested-by: Andy Lutomirski <luto@kernel.org>

--Andy
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#1257677 — [PATCH v2 2/3] virtio_ring: Support DMA APIs

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     | 187 +++++++++++++++++++++++++++++++--------
 tools/virtio/linux/dma-mapping.h |  17 ++++
 3 files changed, 169 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..e71bf0ca59a2 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) {
@@ -200,14 +261,13 @@ 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)) {
 			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, vring_map_one_sg(vq, sg, DMA_TO_DEVICE));
 			desc[i].len = cpu_to_virtio32(_vq->vdev, sg->length);
+			if (vring_mapping_error(vq, desc[i].addr))
+				goto unmap_release;
 			prev = i;
 			i = virtio16_to_cpu(_vq->vdev, desc[i].next);
 		}
@@ -215,8 +275,10 @@ static inline int virtqueue_add(struct virtqueue *_vq,
 	for (; n < (out_sgs + in_sgs); n++) {
 		for (sg = sgs[n]; sg; sg = sg_next(sg)) {
 			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, vring_map_one_sg(vq, sg, DMA_FROM_DEVICE));
 			desc[i].len = cpu_to_virtio32(_vq->vdev, sg->length);
+			if (vring_mapping_error(vq, desc[i].addr))
+				goto unmap_release;
 			prev = i;
 			i = virtio16_to_cpu(_vq->vdev, desc[i].next);
 		}
@@ -224,14 +286,34 @@ 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, vq->vring.desc[head].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 +335,24 @@ 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 +523,43 @@ 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 +614,13 @@ 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 +781,10 @@ 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 +837,8 @@ 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 +868,9 @@ 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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#1257688 — Re: [PATCH v2 2/3] virtio_ring: Support DMA APIs

Am 28.10.2015 um 14:30 schrieb Andy Lutomirski:

> +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);
> +	}
> +}
> +



I still have a failure in this:

[    1.913040] Unable to handle kernel pointer dereference in virtual kernel address space
[    1.913044] failing address: 000000000c800000 TEID: 000000000c800803
[    1.913045] Fault in home space mode while using kernel ASCE.
[    1.913048] AS:0000000000d56007 R3:000000000c7f0007 S:0000000000000020 
[    1.913099] Oops: 0010 ilc:2 [#1] SMP 
[    1.913142] Modules linked in:
[    1.913144] CPU: 4 PID: 50 Comm: kworker/u18:1 Not tainted 4.3.0-rc3+ #252
[    1.913150] Workqueue: events_unbound call_usermodehelper_exec_work
[    1.913152] task: 000000000bb8b310 ti: 000000000bba8000 task.ti: 000000000bba8000
[    1.913154] Krnl PSW : 0404e00180000000 000000000059b266 (vring_unmap_one+0x46/0x8d0)
[    1.913158]            R:0 T:1 IO:0 EX:0 Key:0 M:1 W:0 P:0 AS:3 CC:2 PM:0 EA:3
Krnl GPRS: 0000000000000000 000000000c800000 000000000c036800 000000000c800000
[    1.913161]            00000000005a21a8 0000000000000000 0000000000000000 0000000000000000
[    1.913162]            0704c00180000000 040000000bdbfce8 000000000c082000 000000000bdbf6e8
[    1.913164]            0000000000000400 0000000000000000 000000000bdbf988 000000000bdbf6e8
[    1.913170] Krnl Code: 000000000059b254: e310b0a80004	lg	%r1,168(%r11)
           000000000059b25a: e32010200004	lg	%r2,32(%r1)
          #000000000059b260: e310b0a00004	lg	%r1,160(%r11)
          >000000000059b266: 4810100c		lh	%r1,12(%r1)
           000000000059b26a: e320b2a80024	stg	%r2,680(%r11)
           000000000059b270: 4010b2a6		sth	%r1,678(%r11)
           000000000059b274: e310b2a80004	lg	%r1,680(%r11)
           000000000059b27a: e310b2980024	stg	%r1,664(%r11)
[    1.913183] Call Trace:
[    1.913185] ([<000000000059b74c>] vring_unmap_one+0x52c/0x8d0)
[    1.913187]  [<00000000005a21a8>] detach_buf+0x720/0x788
[    1.913188]  [<00000000005a2830>] virtqueue_get_buf+0x620/0x908
[    1.913191]  [<00000000005e5336>] virtblk_done+0xa6/0x120
[    1.913192]  [<00000000005a3e46>] vring_interrupt+0x2a6/0x2c0
[    1.913224]  [<00000000006c9bdc>] virtio_airq_handler+0x7c/0x120
[    1.913226]  [<000000000065f88c>] do_airq_interrupt+0xa4/0xc8
[    1.913229]  [<00000000001b79a0>] handle_irq_event_percpu+0x60/0x1f0
[    1.913230]  [<00000000001bbbea>] handle_percpu_irq+0x72/0xa0
[    1.913232]  [<00000000001b6fa4>] generic_handle_irq+0x4c/0x78
[    1.913234]  [<000000000010cc7c>] do_IRQ+0x64/0x88
[    1.913236]  [<0000000000815d42>] io_int_handler+0x10a/0x218
[    1.913238]  [<0000000000104268>] copy_thread+0x78/0x1a0
[    1.913240] ([<00000000001548f8>] copy_process.isra.11+0x750/0x1a80)
[    1.913242]  [<0000000000156122>] _do_fork+0x9a/0x338
[    1.913243]  [<000000000015644e>] kernel_thread+0x4e/0x60
[    1.913245]  [<000000000016da7a>] call_usermodehelper_exec_work+0x7a/0xf0
[    1.913247]  [<0000000000171c06>] process_one_work+0x1b6/0x490
[    1.913248]  [<0000000000171f38>] worker_thread+0x58/0x588
[    1.913250]  [<00000000001788fa>] kthread+0x10a/0x110
[    1.913252]  [<0000000000815a8e>] kernel_thread_starter+0x6/0xc
[    1.913254]  [<0000000000815a88>] kernel_thread_starter+0x0/0xc
[    1.913255] Last Breaking-Event-Address:
[    1.913256]  [<00000000005a21a2>] detach_buf+0x71a/0x788
[    1.913258]  
[    1.913263] Kernel panic - not syncing: Fatal exception in interrupt

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#1257690 — Re: [PATCH v2 2/3] virtio_ring: Support DMA APIs

[Multipart message — attachments visible in raw view] — view raw

On Wed, 2015-10-28 at 14:52 +0900, Christian Borntraeger wrote:
>            000000000059b25a: e32010200004       lg      %r2,32(%r1)
>           #000000000059b260: e310b0a00004       lg      %r1,160(%r11)
>           >000000000059b266: 4810100c           lh      %r1,12(%r1)

Precisely what is that? Is that loading ->archdata.dev_ops (offset 160)
from a device and then trying to find the ->unmap_page method therein?

-- 
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#1257805 — Re: [PATCH v2 2/3] virtio_ring: Support DMA APIs

Am 28.10.2015 um 15:04 schrieb David Woodhouse:
> On Wed, 2015-10-28 at 14:52 +0900, Christian Borntraeger wrote:
>>            000000000059b25a: e32010200004       lg      %r2,32(%r1)
>>           #000000000059b260: e310b0a00004       lg      %r1,160(%r11)
>>           >000000000059b266: 4810100c           lh      %r1,12(%r1)
> 
> Precisely what is that? Is that loading ->archdata.dev_ops (offset 160)
> from a device and then trying to find the ->unmap_page method therein?
> 

qemu 2.4 works, and current qemu master has a broken gdb server....I am going to fix
this first.
What I can tell, that the problem goes away if I disable virtio 1.0 so I assume
that things are fine when Andy sends a v4 with the endianess fixes.

Christian

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