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KVM: x86: Add helpers to perform CPUID-based guest vendor check

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Add helpers to provide CPUID-based guest vendor checks, i.e. to do the
ugly register comparisons.  Use the new helpers to check for an AMD
guest vendor in guest_cpuid_is_amd() as well as in the existing emulator
flows.

Using the new helpers fixes a _very_ theoretical bug where
guest_cpuid_is_amd() would get a false positive on a non-AMD virtual CPU
with a vendor string beginning with "Auth" due to the previous logic
only checking EBX.  It also fixes a marginally less theoretically bug
where guest_cpuid_is_amd() would incorrectly return false for a guest
CPU with "AMDisbetter!" as its vendor string.

Fixes: a0c0feb579 ("KVM: x86: reserve bit 8 of non-leaf PDPEs and PML4Es in 64-bit mode on AMD")
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Sean Christopherson
2020-03-04 17:34:32 -08:00
committed by Paolo Bonzini
parent b7fb8488c8
commit 15608ed03f
3 changed files with 33 additions and 29 deletions
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24
arch/x86/kvm/kvm_emulate.h
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@@ -396,6 +396,30 @@ struct x86_emulate_ctxt {
#define X86EMUL_CPUID_VENDOR_GenuineIntel_ecx 0x6c65746e
#define X86EMUL_CPUID_VENDOR_GenuineIntel_edx 0x49656e69
static inline bool is_guest_vendor_intel(u32 ebx, u32 ecx, u32 edx)
{
return ebx == X86EMUL_CPUID_VENDOR_GenuineIntel_ebx &&
ecx == X86EMUL_CPUID_VENDOR_GenuineIntel_ecx &&
edx == X86EMUL_CPUID_VENDOR_GenuineIntel_edx;
}
static inline bool is_guest_vendor_amd(u32 ebx, u32 ecx, u32 edx)
{
return (ebx == X86EMUL_CPUID_VENDOR_AuthenticAMD_ebx &&
ecx == X86EMUL_CPUID_VENDOR_AuthenticAMD_ecx &&
edx == X86EMUL_CPUID_VENDOR_AuthenticAMD_edx) ||
(ebx == X86EMUL_CPUID_VENDOR_AMDisbetterI_ebx &&
ecx == X86EMUL_CPUID_VENDOR_AMDisbetterI_ecx &&
edx == X86EMUL_CPUID_VENDOR_AMDisbetterI_edx);
}
static inline bool is_guest_vendor_hygon(u32 ebx, u32 ecx, u32 edx)
{
return ebx == X86EMUL_CPUID_VENDOR_HygonGenuine_ebx &&
ecx == X86EMUL_CPUID_VENDOR_HygonGenuine_ecx &&
edx == X86EMUL_CPUID_VENDOR_HygonGenuine_edx;
}
enum x86_intercept_stage {
X86_ICTP_NONE = 0, /* Allow zero-init to not match anything */
X86_ICPT_PRE_EXCEPT,