Re: [PATCH v9 4/7] vfio: allow reserved msi iova registration

[Chalamarla, Tirumalesh]

On 5/4/16, 4:54 AM, "linux-arm-kernel on behalf of Eric Auger" <linux-arm-kernel-bounces@xxxxxxxxxxxxxxxxxxx on behalf of eric.auger@xxxxxxxxxx> wrote:

>The user is allowed to register a reserved MSI IOVA range by using the
>DMA MAP API and setting the new flag: VFIO_DMA_MAP_FLAG_MSI_RESERVED_IOVA.
>This region is stored in the vfio_dma rb tree. At that point the iova
>range is not mapped to any target address yet. The host kernel will use
>those iova when needed, typically when MSIs are allocated.
>
>Signed-off-by: Eric Auger <eric.auger@xxxxxxxxxx>
>Signed-off-by: Bharat Bhushan <Bharat.Bhushan@xxxxxxxxxxxxx>
>
>---
>v7 -> v8:
>- use iommu_msi_set_aperture function. There is no notion of
>  unregistration anymore since the reserved msi slot remains
>  until the container gets closed.
>
>v6 -> v7:
>- use iommu_free_reserved_iova_domain
>- convey prot attributes downto dma-reserved-iommu iova domain creation
>- reserved bindings teardown now performed on iommu domain destruction
>- rename VFIO_DMA_MAP_FLAG_MSI_RESERVED_IOVA into
>         VFIO_DMA_MAP_FLAG_RESERVED_MSI_IOVA
>- change title
>- pass the protection attribute to dma-reserved-iommu API
>
>v3 -> v4:
>- use iommu_alloc/free_reserved_iova_domain exported by dma-reserved-iommu
>- protect vfio_register_reserved_iova_range implementation with
>  CONFIG_IOMMU_DMA_RESERVED
>- handle unregistration by user-space and on vfio_iommu_type1 release
>
>v1 -> v2:
>- set returned value according to alloc_reserved_iova_domain result
>- free the iova domains in case any error occurs
>
>RFC v1 -> v1:
>- takes into account Alex comments, based on
>  [RFC PATCH 1/6] vfio: Add interface for add/del reserved iova region:
>- use the existing dma map/unmap ioctl interface with a flag to register
>  a reserved IOVA range. A single reserved iova region is allowed.
>---
> drivers/vfio/vfio_iommu_type1.c | 78 ++++++++++++++++++++++++++++++++++++++++-
> include/uapi/linux/vfio.h       | 10 +++++-
> 2 files changed, 86 insertions(+), 2 deletions(-)
>
>diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
>index 94a9916..4d3a6f1 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/msi-iommu.h>
> 
> #define DRIVER_VERSION  "0.2"
> #define DRIVER_AUTHOR   "Alex Williamson <alex.williamson@xxxxxxxxxx>"
>@@ -445,6 +446,20 @@ static void vfio_unmap_unpin(struct vfio_iommu *iommu, struct vfio_dma *dma)
> 	vfio_lock_acct(-unlocked);
> }
> 
>+static int vfio_set_msi_aperture(struct vfio_iommu *iommu,
>+				dma_addr_t iova, size_t size)
>+{
>+	struct vfio_domain *d;
>+	int ret = 0;
>+
>+	list_for_each_entry(d, &iommu->domain_list, next) {
>+		ret = iommu_msi_set_aperture(d->domain, iova, iova + size - 1);
>+		if (ret)
>+			break;
>+	}
>+	return ret;
>+}
>+
> static void vfio_remove_dma(struct vfio_iommu *iommu, struct vfio_dma *dma)
> {
> 	vfio_unmap_unpin(iommu, dma);
>@@ -693,6 +708,63 @@ static int vfio_dma_do_map(struct vfio_iommu *iommu,
> 	return ret;
> }
> 
>+static int vfio_register_msi_range(struct vfio_iommu *iommu,
>+				   struct vfio_iommu_type1_dma_map *map)
>+{
>+	dma_addr_t iova = map->iova;
>+	size_t size = map->size;
>+	int ret = 0;
>+	struct vfio_dma *dma;
>+	unsigned long order;
>+	uint64_t mask;
>+
>+	/* Verify that none of our __u64 fields overflow */
>+	if (map->size != size || map->iova != iova)
>+		return -EINVAL;
>+
>+	order =  __ffs(vfio_pgsize_bitmap(iommu));
>+	mask = ((uint64_t)1 << order) - 1;
>+
>+	WARN_ON(mask & PAGE_MASK);
>+
>+	if (!size || (size | iova) & mask)
>+		return -EINVAL;
>+
>+	/* Don't allow IOVA address wrap */
>+	if (iova + size - 1 < iova)
>+		return -EINVAL;
>+
>+	mutex_lock(&iommu->lock);
>+
>+	if (vfio_find_dma(iommu, iova, size, VFIO_IOVA_ANY)) {
>+		ret =  -EEXIST;
>+		goto unlock;
>+	}
>+
>+	dma = kzalloc(sizeof(*dma), GFP_KERNEL);
>+	if (!dma) {
>+		ret = -ENOMEM;
>+		goto unlock;
>+	}
>+
>+	dma->iova = iova;
>+	dma->size = size;
>+	dma->type = VFIO_IOVA_RESERVED;
>+
>+	ret = vfio_set_msi_aperture(iommu, iova, size);
>+	if (ret)
>+		goto free_unlock;
>+
>+	vfio_link_dma(iommu, dma);
>+	goto unlock;
>+
>+free_unlock:
>+	kfree(dma);
>+unlock:
>+	mutex_unlock(&iommu->lock);
>+	return ret;
>+}
>+
> static int vfio_bus_type(struct device *dev, void *data)
> {
> 	struct bus_type **bus = data;
>@@ -1062,7 +1134,8 @@ static long vfio_iommu_type1_ioctl(void *iommu_data,
> 	} else if (cmd == VFIO_IOMMU_MAP_DMA) {
> 		struct vfio_iommu_type1_dma_map map;
> 		uint32_t mask = VFIO_DMA_MAP_FLAG_READ |
>-				VFIO_DMA_MAP_FLAG_WRITE;
>+				VFIO_DMA_MAP_FLAG_WRITE |
>+				VFIO_DMA_MAP_FLAG_RESERVED_MSI_IOVA;
> 
> 		minsz = offsetofend(struct vfio_iommu_type1_dma_map, size);
> 
>@@ -1072,6 +1145,9 @@ static long vfio_iommu_type1_ioctl(void *iommu_data,
> 		if (map.argsz < minsz || map.flags & ~mask)
> 			return -EINVAL;
> 
>+		if (map.flags & VFIO_DMA_MAP_FLAG_RESERVED_MSI_IOVA)
>+			return vfio_register_msi_range(iommu, &map);
>+

How are we getting the PA and any validation needed?
> 		return vfio_dma_do_map(iommu, &map);
> 
> 	} else if (cmd == VFIO_IOMMU_UNMAP_DMA) {
>diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
>index 255a211..4a9dbc2 100644
>--- a/include/uapi/linux/vfio.h
>+++ b/include/uapi/linux/vfio.h
>@@ -498,12 +498,19 @@ struct vfio_iommu_type1_info {
>  *
>  * Map process virtual addresses to IO virtual addresses using the
>  * provided struct vfio_dma_map. Caller sets argsz. READ &/ WRITE required.
>+ *
>+ * 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. Once registered, an MSI reserved
>+ * IOVA region stays until the container is closed.
>  */
> struct vfio_iommu_type1_dma_map {
> 	__u32	argsz;
> 	__u32	flags;
> #define VFIO_DMA_MAP_FLAG_READ (1 << 0)		/* readable from device */
> #define VFIO_DMA_MAP_FLAG_WRITE (1 << 1)	/* writable from device */
>+/* reserved iova for MSI vectors*/
>+#define VFIO_DMA_MAP_FLAG_RESERVED_MSI_IOVA (1 << 2)
> 	__u64	vaddr;				/* Process virtual address */
> 	__u64	iova;				/* IO virtual address */
> 	__u64	size;				/* Size of mapping (bytes) */
>@@ -519,7 +526,8 @@ struct vfio_iommu_type1_dma_map {
>  * Caller sets argsz.  The actual unmapped size is returned in the size
>  * field.  No guarantee is made to the user that arbitrary unmaps of iova
>  * or size different from those used in the original mapping call will
>- * succeed.
>+ * succeed. Once registered, an MSI region cannot be unmapped and stays
>+ * until the container is closed.
>  */
> struct vfio_iommu_type1_dma_unmap {
> 	__u32	argsz;
>-- 
>1.9.1
>
>
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