Re: [PATCH v3 7/7] iommu/amd: Do not support IOMMUv2 APIs when SNP is enabled

[Suthikulpanit, Suravee]

On 6/23/2022 3:23 PM, Joerg Roedel wrote:
> On Wed, Jun 22, 2022 at 12:11:31PM -0500, Suravee Suthikulpanit wrote:
> >   bool amd_iommu_v2_supported(void)
> >   {
> > -	return amd_iommu_v2_present;
> > +	/*
> > +	 * Since DTE[Mode]=0 is prohibited on SNP-enabled system
> > +	 * (i.e. EFR[SNPSup]=1), IOMMUv2 page table cannot be used without
> > +	 * setting up IOMMUv1 page table.
> > +	 */
> > +	return amd_iommu_v2_present && !amd_iommu_snp_en;
>
> IOMMU_v2 APIs could actually be supported with GIOV and IOMMUv2
> page-tables in-use, no?
We can support IOMMUv2 iff the v1 table is also setup (i.e. DTE[Mode] != 0).
Currently w/ IOMMU_v2 APIs, the IOMMU sets the mode to zero. Therefore, we
cannot support this use case.

Best Regards,
Suravee