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[PATCH v7 0/7] KVM PCIe/MSI passthrough on ARM/ARM64: kernel part 3/3: vfio changes

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  [PATCH v7 0/7] KVM PCIe/MSI passthrough on ARM/ARM64: kernel part 3/3: vfio changes Eric Auger <eric.auger@linaro.org> - 2016-04-19 19:30 +0200
    [PATCH v7 3/7] vfio/type1: specialize remove_dma and replay according to type Eric Auger <eric.auger@linaro.org> - 2016-04-19 19:30 +0200
    [PATCH v7 7/7] vfio/type1: return MSI mapping requirements with VFIO_IOMMU_GET_INFO Eric Auger <eric.auger@linaro.org> - 2016-04-19 19:30 +0200
    [PATCH v7 1/7] vfio: introduce a vfio_dma type field Eric Auger <eric.auger@linaro.org> - 2016-04-19 19:30 +0200

#1382743 — [PATCH v7 0/7] KVM PCIe/MSI passthrough on ARM/ARM64: kernel part 3/3: vfio changes

This series allows the user-space to register a reserved IOVA domain.
This completes the kernel integration of the whole functionality on top
of part 1 & 2.

We reuse the VFIO DMA MAP ioctl with a new flag to bridge to the
dma-reserved-iommu API. The number of IOVA pages to provision for MSI
binding is reported through the VFIO_IOMMU_GET_INFO iotcl.

vfio_iommu_type1 checks if the MSI mapping is safe when attaching the
vfio group to the container (allow_unsafe_interrupts modality).

On ARM/ARM64, the IOMMU does not astract IRQ remapping. the modality is
abstracted on MSI controller side. The GICv3 ITS is the first controller
advertising the modality.

More details & context can be found at:
http://www.linaro.org/blog/core-dump/kvm-pciemsi-passthrough-armarm64/

Best Regards

Eric

Testing:
- functional on ARM64 AMD Overdrive HW (single GICv2m frame) with
  Intel X540-T2 (SR-IOV capable)
- Not tested: ARM GICv3 ITS

References:
[1] [RFC 0/2] VFIO: Add virtual MSI doorbell support
    (https://lkml.org/lkml/2015/7/24/135)
[2] [RFC PATCH 0/6] vfio: Add interface to map MSI pages
    (https://lists.cs.columbia.edu/pipermail/kvmarm/2015-September/016607.html)
[3] [PATCH v2 0/3] Introduce MSI hardware mapping for VFIO
    (http://permalink.gmane.org/gmane.comp.emulators.kvm.arm.devel/3858)

Git: complete series available at
https://git.linaro.org/people/eric.auger/linux.git/shortlog/refs/heads/v4.6-rc4-pcie-passthrough-v7

previous version at
https://git.linaro.org/people/eric.auger/linux.git/shortlog/refs/heads/v4.6-rc1-pcie-passthrough-v6

QEMU Integration:
[RFC v2 0/8] KVM PCI/MSI passthrough with mach-virt
(http://lists.gnu.org/archive/html/qemu-arm/2016-01/msg00444.html)
https://git.linaro.org/people/eric.auger/qemu.git/shortlog/refs/heads/v2.5.0-pci-passthrough-rfc-v2

History:

v6 -> v7:
- vfio_find_dma now accepts a dma_type argument.
- should have recovered the capability to unmap the whole user IOVA range
- remove computation of nb IOVA pages -> will post a separate RFC for that
  while respinning the QEMU part

RFC v5 -> patch v6:
- split to ease the review process

RFC v4 -> RFC v5:
- take into account Thomas' comments on MSI related patches
  - split "msi: IOMMU map the doorbell address when needed"
  - increase readability and add comments
  - fix style issues
 - split "iommu: Add DOMAIN_ATTR_MSI_MAPPING attribute"
 - platform ITS now advertises IOMMU_CAP_INTR_REMAP
 - fix compilation issue with CONFIG_IOMMU API unset
 - arm-smmu-v3 now advertises DOMAIN_ATTR_MSI_MAPPING

RFC v3 -> v4:
- Move doorbell mapping/unmapping in msi.c
- fix ref count issue on set_affinity: in case of a change in the address
  the previous address is decremented
- doorbell map/unmap now is done on msi composition. Should allow the use
  case for platform MSI controllers
- create dma-reserved-iommu.h/c exposing/implementing a new API dedicated
  to reserved IOVA management (looking like dma-iommu glue)
- series reordering to ease the review:
  - first part is related to IOMMU
  - second related to MSI sub-system
  - third related to VFIO (except arm-smmu IOMMU_CAP_INTR_REMAP removal)
- expose the number of requested IOVA pages through VFIO_IOMMU_GET_INFO
  [this partially addresses Marc's comments on iommu_get/put_single_reserved
   size/alignment problematic - which I did not ignore - but I don't know
   how much I can do at the moment]

RFC v2 -> RFC v3:
- should fix wrong handling of some CONFIG combinations:
  CONFIG_IOVA, CONFIG_IOMMU_API, CONFIG_PCI_MSI_IRQ_DOMAIN
- fix MSI_FLAG_IRQ_REMAPPING setting in GICv3 ITS (although not tested)

PATCH v1 -> RFC v2:
- reverted to RFC since it looks more reasonable ;-) the code is split
  between VFIO, IOMMU, MSI controller and I am not sure I did the right
  choices. Also API need to be further discussed.
- iova API usage in arm-smmu.c.
- MSI controller natively programs the MSI addr with either the PA or IOVA.
  This is not done anymore in vfio-pci driver as suggested by Alex.
- check irq remapping capability of the group

RFC v1 [2] -> PATCH v1:
- use the existing dma map/unmap ioctl interface with a flag to register a
  reserved IOVA range. Use the legacy Rb to store this special vfio_dma.
- a single reserved IOVA contiguous region now is allowed
- use of an RB tree indexed by PA to store allocated reserved slots
- use of a vfio_domain iova_domain to manage iova allocation within the
  window provided by the userspace
- vfio alloc_map/unmap_free take a vfio_group handle
- vfio_group handle is cached in vfio_pci_device
- add ref counting to bindings
- user modality enabled at the end of the series


Eric Auger (7):
  vfio: introduce a vfio_dma type field
  vfio/type1: vfio_find_dma accepting a type argument
  vfio/type1: specialize remove_dma and replay according to type
  vfio: allow reserved iova registration
  vfio/type1: also check IRQ remapping capability at msi domain
  iommu/arm-smmu: do not advertise IOMMU_CAP_INTR_REMAP
  vfio/type1: return MSI mapping requirements with VFIO_IOMMU_GET_INFO

 drivers/iommu/arm-smmu-v3.c     |   3 +-
 drivers/iommu/arm-smmu.c        |   3 +-
 drivers/vfio/vfio_iommu_type1.c | 297 ++++++++++++++++++++++++++++++++++++++--
 include/uapi/linux/vfio.h       |  12 +-
 4 files changed, 298 insertions(+), 17 deletions(-)

-- 
1.9.1

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#1382747 — [PATCH v7 3/7] vfio/type1: specialize remove_dma and replay according to type

Before allowing the end-user to create VFIO_IOVA_RESERVED dma slots,
let's implement the expected behavior for removal and replay. As opposed
to user dma slots, the physical pages bound to reserved IOVA do not need
to be pinned/unpinned. Also we currently handle a single reserved iova
domain. Any attempt to remove the single reserved dma slot ends up
deleting the underlying iova domain for each iommu domain.

Signed-off-by: Eric Auger <eric.auger@linaro.org>
---
 drivers/vfio/vfio_iommu_type1.c | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index 2d769d4..93c17d9 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -36,6 +36,7 @@
 #include <linux/uaccess.h>
 #include <linux/vfio.h>
 #include <linux/workqueue.h>
+#include <linux/dma-reserved-iommu.h>
 
 #define DRIVER_VERSION  "0.2"
 #define DRIVER_AUTHOR   "Alex Williamson <alex.williamson@redhat.com>"
@@ -445,9 +446,20 @@ static void vfio_unmap_unpin(struct vfio_iommu *iommu, struct vfio_dma *dma)
 	vfio_lock_acct(-unlocked);
 }
 
+static void vfio_destroy_reserved(struct vfio_iommu *iommu)
+{
+	struct vfio_domain *d;
+
+	list_for_each_entry(d, &iommu->domain_list, next)
+		iommu_free_reserved_iova_domain(d->domain);
+}
+
 static void vfio_remove_dma(struct vfio_iommu *iommu, struct vfio_dma *dma)
 {
-	vfio_unmap_unpin(iommu, dma);
+	if (likely(dma->type == VFIO_IOVA_USER))
+		vfio_unmap_unpin(iommu, dma);
+	else
+		vfio_destroy_reserved(iommu);
 	vfio_unlink_dma(iommu, dma);
 	kfree(dma);
 }
@@ -727,6 +739,9 @@ static int vfio_iommu_replay(struct vfio_iommu *iommu,
 		dma = rb_entry(n, struct vfio_dma, node);
 		iova = dma->iova;
 
+		if (dma->type == VFIO_IOVA_RESERVED)
+			continue;
+
 		while (iova < dma->iova + dma->size) {
 			phys_addr_t phys = iommu_iova_to_phys(d->domain, iova);
 			size_t size;
-- 
1.9.1

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#1382748 — [PATCH v7 7/7] vfio/type1: return MSI mapping requirements with VFIO_IOMMU_GET_INFO

This patch allows the user-space to know whether MSI addresses need to
be mapped in the IOMMU. The user-space uses VFIO_IOMMU_GET_INFO ioctl and
IOMMU_INFO_REQUIRE_MSI_MAP gets set if they need to.

The computation of the number of IOVA pages to be provided by the user
space will be implemented in a separate patch using capability chains.

Signed-off-by: Eric Auger <eric.auger@linaro.org>

---
v6 -> v7:
- remove the computation of the number of IOVA pages to be provisionned.
  This number depends on the domain/group/device topology which can
  dynamically change. Let's rely instead rely on an arbitrary max depending
  on the system

v4 -> v5:
- move msi_info and ret declaration within the conditional code

v3 -> v4:
- replace former vfio_domains_require_msi_mapping by
  more complex computation of MSI mapping requirements, especially the
  number of pages to be provided by the user-space.
- reword patch title

RFC v1 -> v1:
- derived from
  [RFC PATCH 3/6] vfio: Extend iommu-info to return MSIs automap state
- renamed allow_msi_reconfig into require_msi_mapping
- fixed VFIO_IOMMU_GET_INFO
---
 drivers/vfio/vfio_iommu_type1.c | 24 ++++++++++++++++++++++++
 include/uapi/linux/vfio.h       |  5 ++++-
 2 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index 51b1f15..a63ce6f 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -310,6 +310,27 @@ static int vaddr_get_pfn(unsigned long vaddr, int prot, unsigned long *pfn)
 }
 
 /*
+ * vfio_domains_require_msi_mapping: return whether MSI doorbells must be
+ * iommu mapped
+ *
+ * returns true if msi mapping is requested
+ */
+static bool vfio_domains_require_msi_mapping(struct vfio_iommu *iommu)
+{
+	struct vfio_domain *d;
+	bool flag;
+
+	mutex_lock(&iommu->lock);
+	/* All domains have same require_msi_map property, pick first */
+	d = list_first_entry(&iommu->domain_list, struct vfio_domain, next);
+	flag = (!(iommu_domain_get_attr(d->domain,
+					DOMAIN_ATTR_MSI_MAPPING, NULL)));
+
+	mutex_unlock(&iommu->lock);
+
+	return flag;
+}
+/*
  * Attempt to pin pages.  We really don't want to track all the pfns and
  * the iommu can only map chunks of consecutive pfns anyway, so get the
  * first page and all consecutive pages with the same locking.
@@ -1231,6 +1252,9 @@ static long vfio_iommu_type1_ioctl(void *iommu_data,
 
 		info.flags = VFIO_IOMMU_INFO_PGSIZES;
 
+		if (vfio_domains_require_msi_mapping(iommu))
+			info.flags |= VFIO_IOMMU_INFO_REQUIRE_MSI_MAP;
+
 		info.iova_pgsizes = vfio_pgsize_bitmap(iommu);
 
 		return copy_to_user((void __user *)arg, &info, minsz) ?
diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
index 0637f35..4d9c97d 100644
--- a/include/uapi/linux/vfio.h
+++ b/include/uapi/linux/vfio.h
@@ -488,6 +488,7 @@ struct vfio_iommu_type1_info {
 	__u32	argsz;
 	__u32	flags;
 #define VFIO_IOMMU_INFO_PGSIZES (1 << 0)	/* supported page sizes info */
+#define VFIO_IOMMU_INFO_REQUIRE_MSI_MAP (1 << 1)/* MSI must be mapped */
 	__u64	iova_pgsizes;		/* Bitmap of supported page sizes */
 };
 
@@ -501,7 +502,9 @@ struct vfio_iommu_type1_info {
  *
  * In case RESERVED_MSI_IOVA flag is set, the API only aims at registering an
  * IOVA region that will be used on some platforms to map the host MSI frames.
- * In that specific case, vaddr is ignored.
+ * In that specific case, vaddr is ignored. The requirement for provisioning
+ * such reserved IOVA range can be checked by calling VFIO_IOMMU_GET_INFO and
+ * testing the VFIO_IOMMU_INFO_REQUIRE_MSI_MAP flag.
  */
 struct vfio_iommu_type1_dma_map {
 	__u32	argsz;
-- 
1.9.1

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#1382749 — [PATCH v7 1/7] vfio: introduce a vfio_dma type field

We introduce a vfio_dma type since we will need to discriminate
different types of dma slots:
- VFIO_IOVA_USER: IOVA region used to map user vaddr
- VFIO_IOVA_RESERVED: IOVA region reserved to map host device PA such
  as MSI doorbells

Signed-off-by: Eric Auger <eric.auger@linaro.org>

---

v6 -> v7:
- add VFIO_IOVA_ANY
- do not introduce yet any VFIO_IOVA_RESERVED handling
---
 drivers/vfio/vfio_iommu_type1.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index 75b24e9..aaf5a6c 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -53,6 +53,16 @@ module_param_named(disable_hugepages,
 MODULE_PARM_DESC(disable_hugepages,
 		 "Disable VFIO IOMMU support for IOMMU hugepages.");
 
+enum vfio_iova_type {
+	VFIO_IOVA_USER = 0,	/* standard IOVA used to map user vaddr */
+	/*
+	 * IOVA reserved to map special host physical addresses,
+	 * MSI frames for instance
+	 */
+	VFIO_IOVA_RESERVED,
+	VFIO_IOVA_ANY,		/* matches any IOVA type */
+};
+
 struct vfio_iommu {
 	struct list_head	domain_list;
 	struct mutex		lock;
@@ -75,6 +85,7 @@ struct vfio_dma {
 	unsigned long		vaddr;		/* Process virtual addr */
 	size_t			size;		/* Map size (bytes) */
 	int			prot;		/* IOMMU_READ/WRITE */
+	enum vfio_iova_type	type;		/* type of IOVA */
 };
 
 struct vfio_group {
-- 
1.9.1

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