Commit 15608ed0 authored by Sean Christopherson's avatar Sean Christopherson Committed by Paolo Bonzini
Browse files

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



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: a0c0feb5 ("KVM: x86: reserve bit 8 of non-leaf PDPEs and PML4Es in 64-bit mode on AMD")
Signed-off-by: default avatarSean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent b7fb8488

arch/x86/kvm/cpuid.h

+1 −1
Original line number Diff line number Diff line
@@ -219,7 +219,7 @@ static inline bool guest_cpuid_is_amd(struct kvm_vcpu *vcpu) 
	struct kvm_cpuid_entry2 *best;



	best = kvm_find_cpuid_entry(vcpu, 0, 0);

	return best && best->ebx == X86EMUL_CPUID_VENDOR_AuthenticAMD_ebx;

	return best && is_guest_vendor_amd(best->ebx, best->ecx, best->edx);

}



static inline int guest_cpuid_family(struct kvm_vcpu *vcpu)

arch/x86/kvm/emulate.c

+8 −28
Original line number Diff line number Diff line
@@ -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;



	/*

arch/x86/kvm/kvm_emulate.h

+24 −0
Original line number Diff line number Diff line
@@ -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,

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