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iommu: Redefine IOMMU_CAP_CACHE_COHERENCY as the cap flag for IOMMU_CACHE

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While the comment was correct that this flag was intended to convey the
block no-snoop support in the IOMMU, it has become widely implemented and
used to mean the IOMMU supports IOMMU_CACHE as a map flag. Only the Intel
driver was different.

Now that the Intel driver is using enforce_cache_coherency() update the
comment to make it clear that IOMMU_CAP_CACHE_COHERENCY is only about
IOMMU_CACHE.  Fix the Intel driver to return true since IOMMU_CACHE always
works.

The two places that test this flag, usnic and vdpa, are both assigning
userspace pages to a driver controlled iommu_domain and require
IOMMU_CACHE behavior as they offer no way for userspace to synchronize
caches.

Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Acked-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/3-v3-2cf356649677+a32-intel_no_snoop_jgg@nvidia.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>
This commit is contained in:
Jason Gunthorpe 2022-04-11 12:16:07 -03:00 committed by Joerg Roedel
parent 71cfafda9c
commit f78dc1dad8
2 changed files with 2 additions and 3 deletions
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2
drivers/iommu/intel/iommu.c
View File

@ -4556,7 +4556,7 @@ static bool intel_iommu_enforce_cache_coherency(struct iommu_domain *domain)
static bool intel_iommu_capable(enum iommu_cap cap)
{
if (cap == IOMMU_CAP_CACHE_COHERENCY)
return domain_update_iommu_snooping(NULL);
return true;
if (cap == IOMMU_CAP_INTR_REMAP)
return irq_remapping_enabled == 1;
if (cap == IOMMU_CAP_PRE_BOOT_PROTECTION)

3
include/linux/iommu.h
View File

@ -103,8 +103,7 @@ static inline bool iommu_is_dma_domain(struct iommu_domain *domain)
}
enum iommu_cap {
IOMMU_CAP_CACHE_COHERENCY, /* IOMMU can enforce cache coherent DMA
transactions */
IOMMU_CAP_CACHE_COHERENCY, /* IOMMU_CACHE is supported */
IOMMU_CAP_INTR_REMAP, /* IOMMU supports interrupt isolation */
IOMMU_CAP_NOEXEC, /* IOMMU_NOEXEC flag */
IOMMU_CAP_PRE_BOOT_PROTECTION, /* Firmware says it used the IOMMU for