On Wed, Feb 05, 2025, Vasant Hegde wrote: > On 2/5/2025 8:47 PM, Sean Christopherson wrote: > > On Wed, Feb 05, 2025, Vasant Hegde wrote: > >>> @@ -3318,6 +3326,9 @@ static int __init iommu_go_to_state(enum iommu_init_state state) > >>> ret = state_next(); > >>> } > >>> > >>> + if (ret && !amd_iommu_snp_en && cc_platform_has(CC_ATTR_HOST_SEV_SNP)) > >> > >> > >> I think we should clear when `amd_iommu_snp_en` is true. > > > > That doesn't address the case where amd_iommu_prepare() fails, because amd_iommu_snp_en > > will be %false (its init value) and the RMP will be uninitialized, i.e. > > CC_ATTR_HOST_SEV_SNP will be incorrectly left set. > > You are right. I missed early failure scenarios :-( > > > > > And conversely, IMO clearing CC_ATTR_HOST_SEV_SNP after initializing the IOMMU > > and RMP is wrong as well. Such a host is probably hosed regardless, but from > > the CPU's perspective, SNP is supported and enabled. > > So we don't want to clear CC_ATTR_HOST_SEV_SNP after RMP initialization -OR- > clear for all failures? I honestly don't know, because the answer largely depends on what happens with hardware. I asked in an earlier version of this series if IOMMU initialization failure after the RMP is configured is even survivable. For this series, I think it makes sense to match the existing behavior, unless someone from AMD can definitively state that we should do something different. And the existing behavior is that amd_iommu_snp_en and CC_ATTR_HOST_SEV_SNP will be left set if the IOMMU completes iommu_snp_enable(), and the kernel completes RMP setup.
