Sean, On 2/6/2025 1:01 AM, Sean Christopherson wrote: > 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. Thanks for the clarification. Patch looks OK to me. -Vasant
