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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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36
arch/x86/kvm/emulate.c
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@@ -2723,9 +2723,7 @@ static bool vendor_intel(struct x86_emulate_ctxt *ctxt)
eax = ecx = 0;
ctxt->ops->get_cpuid(ctxt, &eax, &ebx, &ecx, &edx, false);
return ebx == X86EMUL_CPUID_VENDOR_GenuineIntel_ebx
&& ecx == X86EMUL_CPUID_VENDOR_GenuineIntel_ecx
&& edx == X86EMUL_CPUID_VENDOR_GenuineIntel_edx;
return is_guest_vendor_intel(ebx, ecx, edx);
}
static bool em_syscall_is_enabled(struct x86_emulate_ctxt *ctxt)
@@ -2744,34 +2742,16 @@ static bool em_syscall_is_enabled(struct x86_emulate_ctxt *ctxt)
ecx = 0x00000000;
ops->get_cpuid(ctxt, &eax, &ebx, &ecx, &edx, false);
/*
* Intel ("GenuineIntel")
* remark: Intel CPUs only support "syscall" in 64bit
* longmode. Also an 64bit guest with a
* 32bit compat-app running will #UD !! While this
* behaviour can be fixed (by emulating) into AMD
* response - CPUs of AMD can't behave like Intel.
* remark: Intel CPUs only support "syscall" in 64bit longmode. Also a
* 64bit guest with a 32bit compat-app running will #UD !! While this
* behaviour can be fixed (by emulating) into AMD response - CPUs of
* AMD can't behave like Intel.
*/
if (ebx == X86EMUL_CPUID_VENDOR_GenuineIntel_ebx &&
ecx == X86EMUL_CPUID_VENDOR_GenuineIntel_ecx &&
edx == X86EMUL_CPUID_VENDOR_GenuineIntel_edx)
if (is_guest_vendor_intel(ebx, ecx, edx))
return false;
/* AMD ("AuthenticAMD") */
if (ebx == X86EMUL_CPUID_VENDOR_AuthenticAMD_ebx &&
ecx == X86EMUL_CPUID_VENDOR_AuthenticAMD_ecx &&
edx == X86EMUL_CPUID_VENDOR_AuthenticAMD_edx)
return true;
/* AMD ("AMDisbetter!") */
if (ebx == X86EMUL_CPUID_VENDOR_AMDisbetterI_ebx &&
ecx == X86EMUL_CPUID_VENDOR_AMDisbetterI_ecx &&
edx == X86EMUL_CPUID_VENDOR_AMDisbetterI_edx)
return true;
/* Hygon ("HygonGenuine") */
if (ebx == X86EMUL_CPUID_VENDOR_HygonGenuine_ebx &&
ecx == X86EMUL_CPUID_VENDOR_HygonGenuine_ecx &&
edx == X86EMUL_CPUID_VENDOR_HygonGenuine_edx)
if (is_guest_vendor_amd(ebx, ecx, edx) ||
is_guest_vendor_hygon(ebx, ecx, edx))
return true;
/*