From: Jason Gunthorpe <jgg@nvidia.com>
Date: Mon, 11 Apr 2022 12:16:07 -0300
Subject: iommu: Redefine IOMMU_CAP_CACHE_COHERENCY as the cap flag for
IOMMU_CACHE
Git-commit: f78dc1dad829e505d83e33dc0879887f074c52e1
Patch-mainline: v5.19-rc1
References: bsc#1205701
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>
---
drivers/iommu/intel/iommu.c | 2 +-
include/linux/iommu.h | 3 +--
2 files changed, 2 insertions(+), 3 deletions(-)
diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index 38441cb06c8c..efcecfa5952a 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -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)
diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index c7ad6b10e261..575ab27ede5b 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -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