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Reply-To: Sean Christopherson <seanjc@google.com>
Date:   Fri,  8 Jan 2021 16:47:06 -0800
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Subject: [PATCH 05/13] KVM: x86: Override reported SME/SEV feature flags with
 host mask
From:   Sean Christopherson <seanjc@google.com>
To:     Paolo Bonzini <pbonzini@redhat.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Andy Lutomirski <luto@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>
Cc:     Sean Christopherson <seanjc@google.com>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Jim Mattson <jmattson@google.com>,
        Joerg Roedel <joro@8bytes.org>, kvm@vger.kernel.org,
        linux-kernel@vger.kernel.org,
        Tom Lendacky <thomas.lendacky@amd.com>,
        Borislav Petkov <bp@suse.de>,
        Brijesh Singh <brijesh.singh@amd.com>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

Add a reverse-CPUID entry for the memory encryption word, 0x8000001F.EAX,
and use it to override the supported CPUID flags reported to userspace.
Masking the reported CPUID flags avoids over-reporting KVM support, e.g.
without the mask a SEV-SNP capable CPU may incorrectly advertise SNP
support to userspace.

Cc: Brijesh Singh <brijesh.singh@amd.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 arch/x86/kvm/cpuid.c | 2 ++
 arch/x86/kvm/cpuid.h | 1 +
 2 files changed, 3 insertions(+)

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 13036cf0b912..b7618cdd06b5 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -855,6 +855,8 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function)
 	case 0x8000001F:
 		if (!boot_cpu_has(X86_FEATURE_SEV))
 			entry->eax = entry->ebx = entry->ecx = entry->edx = 0;
+		else
+			cpuid_entry_override(entry, CPUID_8000_001F_EAX);
 		break;
 	/*Add support for Centaur's CPUID instruction*/
 	case 0xC0000000:
diff --git a/arch/x86/kvm/cpuid.h b/arch/x86/kvm/cpuid.h
index dc921d76e42e..8b6fc9bde248 100644
--- a/arch/x86/kvm/cpuid.h
+++ b/arch/x86/kvm/cpuid.h
@@ -63,6 +63,7 @@ static const struct cpuid_reg reverse_cpuid[] = {
 	[CPUID_8000_0007_EBX] = {0x80000007, 0, CPUID_EBX},
 	[CPUID_7_EDX]         = {         7, 0, CPUID_EDX},
 	[CPUID_7_1_EAX]       = {         7, 1, CPUID_EAX},
+	[CPUID_8000_001F_EAX] = {0x8000001f, 1, CPUID_EAX},
 };
 
 /*
-- 
2.30.0.284.gd98b1dd5eaa7-goog