RE: [PATCH v12 2/8] iommu/vt-d: Use a helper function to skip agaw for SL

[Tian, Kevin]

> From: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
> Sent: Wednesday, April 22, 2020 2:53 AM
> 
> An Intel iommu domain uses 5-level page table by default. If the
> iommu that the domain tries to attach supports less page levels,
> the top level page tables should be skipped. Add a helper to do
> this so that it could be used in other places.
> 
> Signed-off-by: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
> Reviewed-by: Eric Auger <eric.auger@xxxxxxxxxx>
> ---
>  drivers/iommu/intel-pasid.c | 33 +++++++++++++++++++++++----------
>  1 file changed, 23 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/iommu/intel-pasid.c b/drivers/iommu/intel-pasid.c
> index 22b30f10b396..d9cea3011b58 100644
> --- a/drivers/iommu/intel-pasid.c
> +++ b/drivers/iommu/intel-pasid.c
> @@ -500,6 +500,25 @@ int intel_pasid_setup_first_level(struct intel_iommu
> *iommu,
>  }
> 
>  /*
> + * Skip top levels of page tables for iommu which has less agaw
> + * than default. Unnecessary for PT mode.
> + */
> +static inline int iommu_skip_agaw(struct dmar_domain *domain,
> +				  struct intel_iommu *iommu,
> +				  struct dma_pte **pgd)
> +{
> +	int agaw;
> +
> +	for (agaw = domain->agaw; agaw > iommu->agaw; agaw--) {
> +		*pgd = phys_to_virt(dma_pte_addr(*pgd));
> +		if (!dma_pte_present(*pgd))
> +			return -EINVAL;
> +	}
> +
> +	return agaw;
> +}
> +
> +/*
>   * Set up the scalable mode pasid entry for second only translation type.
>   */
>  int intel_pasid_setup_second_level(struct intel_iommu *iommu,
> @@ -522,17 +541,11 @@ int intel_pasid_setup_second_level(struct
> intel_iommu *iommu,
>  		return -EINVAL;
>  	}
> 
> -	/*
> -	 * Skip top levels of page tables for iommu which has less agaw
> -	 * than default. Unnecessary for PT mode.
> -	 */
>  	pgd = domain->pgd;
> -	for (agaw = domain->agaw; agaw > iommu->agaw; agaw--) {
> -		pgd = phys_to_virt(dma_pte_addr(pgd));
> -		if (!dma_pte_present(pgd)) {
> -			dev_err(dev, "Invalid domain page table\n");
> -			return -EINVAL;
> -		}
> +	agaw = iommu_skip_agaw(domain, iommu, &pgd);
> +	if (agaw < 0) {
> +		dev_err(dev, "Invalid domain page table\n");
> +		return -EINVAL;
>  	}
> 
>  	pgd_val = virt_to_phys(pgd);
> --
> 2.7.4

Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>