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>>> + if (WARN_ON_ONCE(!AMD_IOMMU_GUEST_IR_VAPIC(amd_iommu_guest_ir))) >> + return -EINVAL; >>> >>> iommu->ga_log = iommu_alloc_pages(GFP_KERNEL, get_order(GA_LOG_SIZE)); >>> if (!iommu->ga_log) >>> @@ -2863,8 +2863,10 @@ static void enable_iommus_vapic(void) >>> return; >>> } >>> >>> - if (AMD_IOMMU_GUEST_IR_VAPIC(amd_iommu_guest_ir) && >>> - !check_feature(FEATURE_GAM_VAPIC)) { >>> + if (!AMD_IOMMU_GUEST_IR_VAPIC(amd_iommu_guest_ir)) >>> + return; >>> + >> >> We should move this down after SNP check. Otherwise we may hit WARN_ON_ONCE in >> iommu_init_ga_log(). > > No? enable_iommus_vapic() ends up with: > > 1. if (!AMD_IOMMU_GUEST_IR_VAPIC(amd_iommu_guest_ir)) > return; > > 2. if (!check_feature(FEATURE_GAM_VAPIC)) { > amd_iommu_guest_ir = AMD_IOMMU_GUEST_IR_LEGACY_GA; > return; > } > > 3. if (amd_iommu_snp_en && > !FEATURE_SNPAVICSUP_GAM(amd_iommu_efr2)) { > pr_warn("Force to disable Virtual APIC due to SNP\n"); > amd_iommu_guest_ir = AMD_IOMMU_GUEST_IR_LEGACY_GA; > return; > } Right. I missed the return part. Thanks! Reviewed-by: Vasant Hegde > > /* Enabling GAM and SNPAVIC support */ > for_each_iommu(iommu) { > if (iommu_init_ga_log(iommu) || > iommu_ga_log_enable(iommu)) > return; > > iommu_feature_enable(iommu, CONTROL_GAM_EN); > if (amd_iommu_snp_en) > iommu_feature_enable(iommu, CONTROL_SNPAVIC_EN); > } > > And that's the only call site for iommu_init_ga_log(). Getting past #1 guarantees > "amd_iommu_guest_ir == AMD_IOMMU_GUEST_IR_VAPIC", and if #2 and #3 return early > if they modify amd_iommu_guest_ir, so it should be impossible for iommu_init_ga_log() > to be called with amd_iommu_guest_ir anything other than AMD_IOMMU_GUEST_IR_VAPIC. > > Shifting the initial check down isn't functionally correct, as it wouldn't do the > right thing if amd_iommu_guest_ir==AMD_IOMMU_GUEST_IR_LEGACY. AFAICT, nothing > prevents calling into enable_iommus_vapic() in that case. Right. I will add fix to move #2 to iommu_init_pci() and #3 to iommu_snp_enable() . -Vasant