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vfio iommu: Add dma available capability

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[ Upstream commit 7d6e1329652ed971d1b6e0e7bea66fba5044e271 ]

The following functional changes were needed for backport:
- vfio_iommu_type1_get_info doesn't exist, call
  vfio_iommu_dma_avail_build_caps from vfio_iommu_type1_ioctl.
- As further fallout from this, vfio_iommu_dma_avail_build_caps must
  acquire and release the iommu mutex lock.  To do so, the return value is
  stored in a local variable as in vfio_iommu_iova_build_caps.

Upstream commit description:
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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Matthew Rosato 2021-01-11 12:31:28 -05:00 • committed by Greg Kroah-Hartman
commit 5597557244
2 changed files with 37 additions and 0 deletions
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15
include/uapi/linux/vfio.h
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@ -748,6 +748,21 @@ struct vfio_iommu_type1_info_cap_iova_range {
struct vfio_iova_range iova_ranges[];
};
/*
* 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)
/**