Re: [PATCH v3 4/7] iommu/vt-d: Handle non-page aligned address

[Auger Eric]

Hi Jacob,

On 7/1/20 5:33 PM, Jacob Pan wrote:
> From: Liu Yi L <yi.l.liu@xxxxxxxxx>
> 
> Address information for device TLB invalidation comes from userspace
> when device is directly assigned to a guest with vIOMMU support.
> VT-d requires page aligned address. This patch checks and enforce
> address to be page aligned, otherwise reserved bits can be set in the
> invalidation descriptor. Unrecoverable fault will be reported due to
> non-zero value in the reserved bits.
on the other hand if user space sends unaligned invalidations, shouldn't
it be reported in some way?
> 
> Fixes: 61a06a16e36d8 ("iommu/vt-d: Support flushing more translation
> cache types")
> Acked-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
> Signed-off-by: Liu Yi L <yi.l.liu@xxxxxxxxx>
> Signed-off-by: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
> 
> Signed-off-by: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
> ---
>  drivers/iommu/intel/dmar.c | 20 ++++++++++++++++++--
>  1 file changed, 18 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/iommu/intel/dmar.c b/drivers/iommu/intel/dmar.c
> index d9f973fa1190..3899f3161071 100644
> --- a/drivers/iommu/intel/dmar.c
> +++ b/drivers/iommu/intel/dmar.c
> @@ -1455,9 +1455,25 @@ void qi_flush_dev_iotlb_pasid(struct intel_iommu *iommu, u16 sid, u16 pfsid,
>  	 * Max Invs Pending (MIP) is set to 0 for now until we have DIT in
>  	 * ECAP.
>  	 */
> -	desc.qw1 |= addr & ~mask;
> -	if (size_order)
> +	if (addr & ~VTD_PAGE_MASK)
> +		pr_warn_ratelimited("Invalidate non-page aligned address %llx\n", addr);
> +
> +	/* Take page address */
> +	desc.qw1 |= QI_DEV_EIOTLB_ADDR(addr);
> +
> +	if (size_order) {
> +		/*
> +		 * Existing 0s in address below size_order may be the least
> +		 * significant bit, we must set them to 1s to avoid having
> +		 * smaller size than desired.
Shouldn't you test the input addr against the size_order. Aren't they
supposed to be consistent? Otherwise one should emit a warning at least?
> +		 */
> +		desc.qw1 |= GENMASK_ULL(size_order + VTD_PAGE_SHIFT,
> +					VTD_PAGE_SHIFT);
nit: instead of working directly on .qw1, couldn't you perform all those
manipulations directly on addr? and eventually override qw1 at the end?
> +		/* Clear size_order bit to indicate size */
> +		desc.qw1 &= ~mask;
> +		/* Set the S bit to indicate flushing more than 1 page */
>  		desc.qw1 |= QI_DEV_EIOTLB_SIZE;
> +	}
>  
>  	qi_submit_sync(iommu, &desc, 1, 0);
>  }
> 
Thanks

Eric