Commit f78dc1da authored by Jason Gunthorpe's avatar Jason Gunthorpe Committed by Joerg Roedel
Browse files

iommu: Redefine IOMMU_CAP_CACHE_COHERENCY as the cap flag for IOMMU_CACHE 



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: default avatarKevin Tian <kevin.tian@intel.com>
Reviewed-by: default avatarLu Baolu <baolu.lu@linux.intel.com>
Acked-by: default avatarRobin Murphy <robin.murphy@arm.com>
Signed-off-by: default avatarJason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/3-v3-2cf356649677+a32-intel_no_snoop_jgg@nvidia.com


Signed-off-by: default avatarJoerg Roedel <jroedel@suse.de>
parent 71cfafda

drivers/iommu/intel/iommu.c

+1 −1
Original line number Diff line number Diff line
@@ -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)

include/linux/iommu.h

+1 −2
Original line number Diff line number Diff line
@@ -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