linux-kernel - [PATCH v2 5/7] KVM: x86: Add build-time assertions on validity of vendor strings

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Date:   Wed,  4 Mar 2020 17:34:35 -0800
From:   Sean Christopherson <sean.j.christopherson@...el.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Sean Christopherson <sean.j.christopherson@...el.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Pu Wen <puwen@...on.cn>
Subject: [PATCH v2 5/7] KVM: x86: Add build-time assertions on validity of vendor strings

Add build-time assertions on the transcoded ASCII->u32 values for the
vendor strings.  The u32 values are inscrutable, and to make things
worse, the order of registers used to build the strings is B->D->C,
i.e. completely illogical.

Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
---
 arch/x86/kvm/emulate.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 9cf303984fe5..7391e1471e53 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -3952,6 +3952,26 @@ static int em_cpuid(struct x86_emulate_ctxt *ctxt)
 	u32 eax, ebx, ecx, edx;
 	u64 msr = 0;
 
+	BUILD_BUG_ON(X86EMUL_CPUID_VENDOR_AuthenticAMD_ebx != *(u32 *)"Auth" ||
+		     X86EMUL_CPUID_VENDOR_AuthenticAMD_edx != *(u32 *)"enti" ||
+		     X86EMUL_CPUID_VENDOR_AuthenticAMD_ecx != *(u32 *)"cAMD");
+
+	BUILD_BUG_ON(X86EMUL_CPUID_VENDOR_AMDisbetterI_ebx != *(u32 *)"AMDi" ||
+		     X86EMUL_CPUID_VENDOR_AMDisbetterI_edx != *(u32 *)"sbet" ||
+		     X86EMUL_CPUID_VENDOR_AMDisbetterI_ecx != *(u32 *)"ter!");
+
+	BUILD_BUG_ON(X86EMUL_CPUID_VENDOR_HygonGenuine_ebx != *(u32 *)"Hygo" ||
+		     X86EMUL_CPUID_VENDOR_HygonGenuine_edx != *(u32 *)"nGen" ||
+		     X86EMUL_CPUID_VENDOR_HygonGenuine_ecx != *(u32 *)"uine");
+
+	BUILD_BUG_ON(X86EMUL_CPUID_VENDOR_GenuineIntel_ebx != *(u32 *)"Genu" ||
+		     X86EMUL_CPUID_VENDOR_GenuineIntel_edx != *(u32 *)"ineI" ||
+		     X86EMUL_CPUID_VENDOR_GenuineIntel_ecx != *(u32 *)"ntel");
+
+	BUILD_BUG_ON(X86EMUL_CPUID_VENDOR_CentaurHauls_ebx != *(u32 *)"Cent" ||
+		     X86EMUL_CPUID_VENDOR_CentaurHauls_edx != *(u32 *)"aurH" ||
+		     X86EMUL_CPUID_VENDOR_CentaurHauls_ecx != *(u32 *)"auls");
+
 	ctxt->ops->get_msr(ctxt, MSR_MISC_FEATURES_ENABLES, &msr);
 	if (msr & MSR_MISC_FEATURES_ENABLES_CPUID_FAULT &&
 	    ctxt->ops->cpl(ctxt)) {
-- 
2.24.1