[PATCH 1/1] iommu/vt-d: Use real PASID for flush in caching mode

[PATCH 1/1] iommu/vt-d: Use real PASID for flush in caching mode

[Lu Baolu]

If caching mode is supported, the hardware will cache
none-present or erroneous translation entries. Hence,
software should explicitly invalidate the PASID cache
after a PASID table entry becomes present. We should
issue such invalidation with the PASID value that we
have changed. PASID 0 is not reserved for this case.

Cc: Jacob Pan <jacob.jun.pan@linux.intel.com>
Cc: Kevin Tian <kevin.tian@intel.com>
Cc: Sankaran Rajesh <rajesh.sankaran@intel.com>
Suggested-by: Ashok Raj <ashok.raj@intel.com>
Signed-off-by: Liu Yi L <yi.l.liu@intel.com>
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
---
 drivers/iommu/intel-svm.c | 16 ++++++----------
 1 file changed, 6 insertions(+), 10 deletions(-)

diff --git a/drivers/iommu/intel-svm.c b/drivers/iommu/intel-svm.c
index 99bc9bd..b7b88b5 100644
--- a/drivers/iommu/intel-svm.c
+++ b/drivers/iommu/intel-svm.c
@@ -422,17 +422,13 @@ int intel_svm_bind_mm(struct device *dev, int *pasid, int flags, struct svm_dev_
 		iommu->pasid_table[svm->pasid].val = pasid_entry_val;
 
 		wmb();
-		/* In caching mode, we still have to flush with PASID 0 when
-		 * a PASID table entry becomes present. Not entirely clear
-		 * *why* that would be the case — surely we could just issue
-		 * a flush with the PASID value that we've changed? The PASID
-		 * is the index into the table, after all. It's not like domain
-		 * IDs in the case of the equivalent context-entry change in
-		 * caching mode. And for that matter it's not entirely clear why
-		 * a VMM would be in the business of caching the PASID table
-		 * anyway. Surely that can be left entirely to the guest? */
+
+		/*
+		 * Flush PASID cache when a PASID table entry becomes
+		 * present.
+		 */
 		if (cap_caching_mode(iommu->cap))
-			intel_flush_pasid_dev(svm, sdev, 0);
+			intel_flush_pasid_dev(svm, sdev, svm->pasid);
 	}
 	list_add_rcu(&sdev->list, &svm->devs);
 
-- 
2.7.4

Re: [PATCH 1/1] iommu/vt-d: Use real PASID for flush in caching mode

[Joerg Roedel]

On Fri, Mar 16, 2018 at 12:31:36PM +0800, Lu Baolu wrote:
> If caching mode is supported, the hardware will cache
> none-present or erroneous translation entries. Hence,
> software should explicitly invalidate the PASID cache
> after a PASID table entry becomes present. We should
> issue such invalidation with the PASID value that we
> have changed. PASID 0 is not reserved for this case.
> 
> Cc: Jacob Pan <jacob.jun.pan@linux.intel.com>
> Cc: Kevin Tian <kevin.tian@intel.com>
> Cc: Sankaran Rajesh <rajesh.sankaran@intel.com>
> Suggested-by: Ashok Raj <ashok.raj@intel.com>
> Signed-off-by: Liu Yi L <yi.l.liu@intel.com>
> Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
> ---
>  drivers/iommu/intel-svm.c | 16 ++++++----------
>  1 file changed, 6 insertions(+), 10 deletions(-)

Applied, thanks.