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vfio iommu: Add dma available capability 

Commit 492855939b ("vfio/type1: Limit DMA mappings per container")
added the ability to limit the number of memory backed DMA mappings.
However on s390x, when lazy mapping is in use, we use a very large
number of concurrent mappings.  Let's provide the current allowable
number of DMA mappings to userspace via the IOMMU info chain so that
userspace can take appropriate mitigation.

Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
This commit is contained in:
Matthew Rosato 2020-09-15 15:05:18 -04:00 committed by Alex Williamson
parent ba4f184e12
commit 7d6e132965
2 changed files with 32 additions and 0 deletions
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17
drivers/vfio/vfio_iommu_type1.c
View File

@ -2609,6 +2609,20 @@ static int vfio_iommu_migration_build_caps(struct vfio_iommu *iommu,
return vfio_info_add_capability(caps, &cap_mig.header, sizeof(cap_mig)); return vfio_info_add_capability(caps, &cap_mig.header, sizeof(cap_mig));
} }
static int vfio_iommu_dma_avail_build_caps(struct vfio_iommu *iommu,
struct vfio_info_cap *caps)
{
struct vfio_iommu_type1_info_dma_avail cap_dma_avail;
cap_dma_avail.header.id = VFIO_IOMMU_TYPE1_INFO_DMA_AVAIL;
cap_dma_avail.header.version = 1;
cap_dma_avail.avail = iommu->dma_avail;
return vfio_info_add_capability(caps, &cap_dma_avail.header,
sizeof(cap_dma_avail));
}
static int vfio_iommu_type1_get_info(struct vfio_iommu *iommu, static int vfio_iommu_type1_get_info(struct vfio_iommu *iommu,
unsigned long arg) unsigned long arg)
{ {
@ -2641,6 +2655,9 @@ static int vfio_iommu_type1_get_info(struct vfio_iommu *iommu,
ret = vfio_iommu_migration_build_caps(iommu, &caps); ret = vfio_iommu_migration_build_caps(iommu, &caps);
if (!ret)
ret = vfio_iommu_dma_avail_build_caps(iommu, &caps);
if (!ret) if (!ret)
ret = vfio_iommu_iova_build_caps(iommu, &caps); ret = vfio_iommu_iova_build_caps(iommu, &caps);

15
include/uapi/linux/vfio.h
View File

@ -1039,6 +1039,21 @@ struct vfio_iommu_type1_info_cap_migration {
__u64 max_dirty_bitmap_size; /* in bytes */ __u64 max_dirty_bitmap_size; /* in bytes */
}; };
/*
* The DMA available capability allows to report the current number of
* simultaneously outstanding DMA mappings that are allowed.
*
* The structure below defines version 1 of this capability.
*
* avail: specifies the current number of outstanding DMA mappings allowed.
*/
#define VFIO_IOMMU_TYPE1_INFO_DMA_AVAIL 3
struct vfio_iommu_type1_info_dma_avail {
struct vfio_info_cap_header header;
__u32 avail;
};
#define VFIO_IOMMU_GET_INFO _IO(VFIO_TYPE, VFIO_BASE + 12) #define VFIO_IOMMU_GET_INFO _IO(VFIO_TYPE, VFIO_BASE + 12)
/** /**