Re: [PATCH v2 1/4] iommu/vt-d: Enable write protect for supervisor SVM

[Lu Baolu]

On 3/2/21 6:13 PM, Jacob Pan wrote:
> Write protect bit, when set, inhibits supervisor writes to the read-only
> pages. In supervisor shared virtual addressing (SVA), where page tables
> are shared between CPU and DMA, IOMMU PASID entry WPE bit should match
> CR0.WP bit in the CPU.
> This patch sets WPE bit for supervisor PASIDs if CR0.WP is set.
>
> Signed-off-by: Sanjay Kumar <sanjay.k.kumar@xxxxxxxxx>
> Signed-off-by: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
> ---
>   drivers/iommu/intel/pasid.c | 26 ++++++++++++++++++++++++++
>   1 file changed, 26 insertions(+)
>
> diff --git a/drivers/iommu/intel/pasid.c b/drivers/iommu/intel/pasid.c
> index 0cceaabc3ce6..0b7e0e726ade 100644
> --- a/drivers/iommu/intel/pasid.c
> +++ b/drivers/iommu/intel/pasid.c
> @@ -410,6 +410,15 @@ static inline void pasid_set_sre(struct pasid_entry *pe)
>   	pasid_set_bits(&pe->val[2], 1 << 0, 1);
>   }
>   
> +/*
> + * Setup the WPE(Write Protect Enable) field (Bit 132) of a
> + * scalable mode PASID entry.
> + */
> +static inline void pasid_set_wpe(struct pasid_entry *pe)
> +{
> +	pasid_set_bits(&pe->val[2], 1 << 4, 1 << 4);
> +}
> +
>   /*
>    * Setup the P(Present) field (Bit 0) of a scalable mode PASID
>    * entry.
> @@ -553,6 +562,20 @@ static void pasid_flush_caches(struct intel_iommu *iommu,
>   	}
>   }
>   
> +static inline int pasid_enable_wpe(struct pasid_entry *pte)
> +{
> +	unsigned long cr0 = read_cr0();
> +
> +	/* CR0.WP is normally set but just to be sure */
> +	if (unlikely(!(cr0 & X86_CR0_WP))) {
> +		pr_err_ratelimited("No CPU write protect!\n");
> +		return -EINVAL;
> +	}
> +	pasid_set_wpe(pte);
> +
> +	return 0;
> +};
> +
>   /*
>    * Set up the scalable mode pasid table entry for first only
>    * translation type.
> @@ -584,6 +607,9 @@ int intel_pasid_setup_first_level(struct intel_iommu *iommu,
>   			return -EINVAL;
>   		}
>   		pasid_set_sre(pte);
> +		if (pasid_enable_wpe(pte))
> +			return -EINVAL;
> +
>   	}
>   
>   	if (flags & PASID_FLAG_FL5LP) {

Acked-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>

Best regards,
baolu