On Wed, May 12, 2021 at 02:44:26PM +0800, Lu Baolu wrote:
> When first-level page tables are used for IOVA translation, we use user
> privilege by setting U/S bit in the page table entry. This is to make it
> consistent with the second level translation, where the U/S enforcement
> is not available. Clear the SRE (Supervisor Request Enable) field in the
> pasid table entry of RID2PASID so that requests requesting the supervisor
> privilege are blocked and treated as DMA remapping faults.
> 
> Suggested-by: Jacob Pan <jacob.jun....@linux.intel.com>
> Fixes: b802d070a52a1 ("iommu/vt-d: Use iova over first level")
> Signed-off-by: Lu Baolu <baolu...@linux.intel.com>
> ---
>  drivers/iommu/intel/iommu.c | 7 +++++--
>  drivers/iommu/intel/pasid.c | 3 ++-
>  2 files changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
> index 708f430af1c4..f1742da42478 100644
> --- a/drivers/iommu/intel/iommu.c
> +++ b/drivers/iommu/intel/iommu.c
> @@ -2525,9 +2525,9 @@ static int domain_setup_first_level(struct intel_iommu 
> *iommu,
>                                   struct device *dev,
>                                   u32 pasid)
>  {
> -     int flags = PASID_FLAG_SUPERVISOR_MODE;
>       struct dma_pte *pgd = domain->pgd;
>       int agaw, level;
> +     int flags = 0;
>  
>       /*
>        * Skip top levels of page tables for iommu which has
> @@ -2543,7 +2543,10 @@ static int domain_setup_first_level(struct intel_iommu 
> *iommu,
>       if (level != 4 && level != 5)
>               return -EINVAL;
>  
> -     flags |= (level == 5) ? PASID_FLAG_FL5LP : 0;
> +     if (pasid != PASID_RID2PASID)
> +             flags |= PASID_FLAG_SUPERVISOR_MODE;
> +     if (level == 5)
> +             flags |= PASID_FLAG_FL5LP;

Given that we are still not bought into the supervisor PASID, should we make 
this an 
explicit request before turning on SUPERVISOR mode always? Since
pasid_set_sre() has no return, we have no way to fail it.



>  
>       if (domain->domain.type == IOMMU_DOMAIN_UNMANAGED)
>               flags |= PASID_FLAG_PAGE_SNOOP;
> diff --git a/drivers/iommu/intel/pasid.c b/drivers/iommu/intel/pasid.c
> index 72646bafc52f..72dc84821dad 100644
> --- a/drivers/iommu/intel/pasid.c
> +++ b/drivers/iommu/intel/pasid.c
> @@ -699,7 +699,8 @@ int intel_pasid_setup_second_level(struct intel_iommu 
> *iommu,
>        * Since it is a second level only translation setup, we should
>        * set SRE bit as well (addresses are expected to be GPAs).
>        */
> -     pasid_set_sre(pte);
> +     if (pasid != PASID_RID2PASID)
> +             pasid_set_sre(pte);
>       pasid_set_present(pte);
>       pasid_flush_caches(iommu, pte, pasid, did);
>  
> -- 
> 2.25.1
> 

-- 
Cheers,
Ashok

[Forgiveness is the attribute of the STRONG - Gandhi]
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