iommu/vt-d: Remove caching mode check before device TLB flush

The Caching Mode (CM) of the Intel IOMMU indicates if the hardware
implementation caches not-present or erroneous translation-structure
entries except for the first-stage translation. The caching mode is
irrelevant to the device TLB, therefore there is no need to check it
before a device TLB invalidation operation.

Remove two caching mode checks before device TLB invalidation in the
driver. The removal of these checks doesn't change the driver's behavior
in critical map/unmap paths. Hence, there is no functionality or
performance impact, especially since commit <29b32839725f> ("iommu/vt-d:
Do not use flush-queue when caching-mode is on") has already disabled
flush-queue for caching mode. Therefore, caching mode will never call
intel_flush_iotlb_all().

Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Reviewed-by: Yi Liu <yi.l.liu@intel.com>
Link: https://lore.kernel.org/r/20240415013835.9527-1-baolu.lu@linux.intel.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>

diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index 4a2afe89b464d191091e107c01de54e00c3f0a2e..002fee5fcb80dec56b630f5c2499fefbaece0217 100644 (file)
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -1502,11 +1502,7 @@ static void iommu_flush_iotlb_psi(struct intel_iommu *iommu,
        else
                __iommu_flush_iotlb_psi(iommu, did, pfn, pages, ih);
 
-       /*
-        * In caching mode, changes of pages from non-present to present require
-        * flush. However, device IOTLB doesn't need to be flushed in this case.
-        */
-       if (!cap_caching_mode(iommu->cap) || !map)
+       if (!map)
                iommu_flush_dev_iotlb(domain, addr, mask);
 }
 
@@ -1580,8 +1576,7 @@ static void intel_flush_iotlb_all(struct iommu_domain *domain)
                        iommu->flush.flush_iotlb(iommu, did, 0, 0,
                                                 DMA_TLB_DSI_FLUSH);
 
-               if (!cap_caching_mode(iommu->cap))
-                       iommu_flush_dev_iotlb(dmar_domain, 0, MAX_AGAW_PFN_WIDTH);
+               iommu_flush_dev_iotlb(dmar_domain, 0, MAX_AGAW_PFN_WIDTH);
        }
 
        if (dmar_domain->nested_parent)