2023-03-31 23:08:53

by Jacob Pan

Subject: [PATCH v3 1/7] iommu/vt-d: Use non-privileged mode for all PASIDs

Supervisor Request Enable (SRE) bit in a PASID entry is for permission
checking on DMA requests. When SRE = 0, DMA with supervisor privilege
will be blocked. However, for in-kernel DMA this is not necessary in that
we are targeting kernel memory anyway. There's no need to differentiate
user and kernel for in-kernel DMA.

Let's use non-privileged (user) permission for all PASIDs used in kernel,
it will be consistent with DMA without PASID (RID_PASID) as well.

Signed-off-by: Jacob Pan <[email protected]>
---
drivers/iommu/intel/iommu.c | 2 --
1 file changed, 2 deletions(-)

diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index 0768dcae90fd..9f737ef55463 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -2338,8 +2338,6 @@ static int domain_setup_first_level(struct intel_iommu *iommu,
if (level != 4 && level != 5)
return -EINVAL;

- if (pasid != PASID_RID2PASID)
- flags |= PASID_FLAG_SUPERVISOR_MODE;
if (level == 5)
flags |= PASID_FLAG_FL5LP;

--
2.25.1

2023-04-01 13:43:36

by Lu Baolu

Subject: Re: [PATCH v3 1/7] iommu/vt-d: Use non-privileged mode for all PASIDs

On 2023/4/1 7:11, Jacob Pan wrote:
> Supervisor Request Enable (SRE) bit in a PASID entry is for permission
> checking on DMA requests. When SRE = 0, DMA with supervisor privilege
> will be blocked. However, for in-kernel DMA this is not necessary in that
> we are targeting kernel memory anyway. There's no need to differentiate
> user and kernel for in-kernel DMA.
>
> Let's use non-privileged (user) permission for all PASIDs used in kernel,
> it will be consistent with DMA without PASID (RID_PASID) as well.
>
> Signed-off-by: Jacob Pan<[email protected]>

Reviewed-by: Lu Baolu <[email protected]>

Best regards,
baolu