[PATCH 3/5] iommu/vt-d: Preset A/D bits for user space DMA usage

Lu Baolu
2021-07-20T01:46:23Z

We preset the access and dirty bits for IOVA over first level usage only
for the kernel DMA (i.e., when domain type is IOMMU_DOMAIN_DMA). We should
also preset the FL A/D for user space DMA usage. The idea is that even the
user space A/D bit memory write is unnecessary. We should avoid it to
minimize the overhead.

Suggested-by: Sanjay Kumar <sanjay.k.kumar@intel.com>
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
---
drivers/iommu/intel/iommu.c | 10 +++-------
1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index 1131b8efb050..f45c80ce2381 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -2339,13 +2339,9 @@ __domain_mapping(struct dmar_domain *domain, unsigned long iov_pfn,
attr = prot & (DMA_PTE_READ | DMA_PTE_WRITE | DMA_PTE_SNP);
attr |= DMA_FL_PTE_PRESENT;
if (domain_use_first_level(domain)) {
- attr |= DMA_FL_PTE_XD | DMA_FL_PTE_US;
-
- if (domain->domain.type == IOMMU_DOMAIN_DMA) {
- attr |= DMA_FL_PTE_ACCESS;
- if (prot & DMA_PTE_WRITE)
- attr |= DMA_FL_PTE_DIRTY;
- }
+ attr |= DMA_FL_PTE_XD | DMA_FL_PTE_US | DMA_FL_PTE_ACCESS;
+ if (prot & DMA_PTE_WRITE)
+ attr |= DMA_FL_PTE_DIRTY;
}

pteval = ((phys_addr_t)phys_pfn << VTD_PAGE_SHIFT) | attr;
--
2.25.1