Re: [PATCH v3 3/7] iommu/vt-d: Fix PASID devTLB invalidation

Auger Eric
2020-07-02T07:16:34Z

Hi Jacob,

On 7/1/20 5:33 PM, Jacob Pan wrote:
> DevTLB flush can be used for both DMA request with and without PASIDs.
> The former uses PASID#0 (RID2PASID), latter uses non-zero PASID for SVA
> usage.
>
> This patch adds a check for PASID value such that devTLB flush with
> PASID is used for SVA case. This is more efficient in that multiple
> PASIDs can be used by a single device, when tearing down a PASID entry
> we shall flush only the devTLB specific to a PASID.
>
> Fixes: 6f7db75e1c46 ("iommu/vt-d: Add second level page table")
> Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>

Thanks

Eric
> ---
> drivers/iommu/intel/pasid.c | 11 ++++++++++-
> 1 file changed, 10 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/iommu/intel/pasid.c b/drivers/iommu/intel/pasid.c
> index c81f0f17c6ba..fa0154cce537 100644
> --- a/drivers/iommu/intel/pasid.c
> +++ b/drivers/iommu/intel/pasid.c
> @@ -486,7 +486,16 @@ devtlb_invalidation_with_pasid(struct intel_iommu *iommu,
> qdep = info->ats_qdep;
> pfsid = info->pfsid;
>
> - qi_flush_dev_iotlb(iommu, sid, pfsid, qdep, 0, 64 - VTD_PAGE_SHIFT);
> + /*
> + * When PASID 0 is used, it indicates RID2PASID(DMA request w/o PASID),
> + * devTLB flush w/o PASID should be used. For non-zero PASID under
> + * SVA usage, device could do DMA with multiple PASIDs. It is more
> + * efficient to flush devTLB specific to the PASID.
> + */
> + if (pasid == PASID_RID2PASID)
> + qi_flush_dev_iotlb(iommu, sid, pfsid, qdep, 0, 64 - VTD_PAGE_SHIFT);
> + else
> + qi_flush_dev_iotlb_pasid(iommu, sid, pfsid, pasid, qdep, 0, 64 - VTD_PAGE_SHIFT);
> }
>
> void intel_pasid_tear_down_entry(struct intel_iommu *iommu, struct device *dev,
>