Commit 76ea438b authored by Paolo Bonzini's avatar Paolo Bonzini
Browse files

KVM: X86: Expose bus lock debug exception to guest 



Bus lock debug exception is an ability to notify the kernel by an #DB
trap after the instruction acquires a bus lock and is executed when
CPL>0. This allows the kernel to enforce user application throttling or
mitigations.

Existence of bus lock debug exception is enumerated via
CPUID.(EAX=7,ECX=0).ECX[24]. Software can enable these exceptions by
setting bit 2 of the MSR_IA32_DEBUGCTL. Expose the CPUID to guest and
emulate the MSR handling when guest enables it.

Support for this feature was originally developed by Xiaoyao Li and
Chenyi Qiang, but code has since changed enough that this patch has
nothing in common with theirs, except for this commit message.

Co-developed-by: default avatarXiaoyao Li <xiaoyao.li@intel.com>
Signed-off-by: default avatarXiaoyao Li <xiaoyao.li@intel.com>
Signed-off-by: default avatarChenyi Qiang <chenyi.qiang@intel.com>
Message-Id: <20210202090433.13441-4-chenyi.qiang@intel.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent e8ea85fb

arch/x86/kvm/cpuid.c

+1 −1
Original line number Diff line number Diff line
@@ -458,7 +458,7 @@ void kvm_set_cpu_caps(void) 
		F(AVX512_VPOPCNTDQ) | F(UMIP) | F(AVX512_VBMI2) | F(GFNI) |

		F(VAES) | F(VPCLMULQDQ) | F(AVX512_VNNI) | F(AVX512_BITALG) |

		F(CLDEMOTE) | F(MOVDIRI) | F(MOVDIR64B) | 0 /*WAITPKG*/ |

		F(SGX_LC)

		F(SGX_LC) | F(BUS_LOCK_DETECT)

	);

	/* Set LA57 based on hardware capability. */

	if (cpuid_ecx(7) & F(LA57))

arch/x86/kvm/vmx/capabilities.h

+3 −0
Original line number Diff line number Diff line
@@ -398,6 +398,9 @@ static inline u64 vmx_supported_debugctl(void) 
{

	u64 debugctl = 0;



	if (boot_cpu_has(X86_FEATURE_BUS_LOCK_DETECT))

		debugctl |= DEBUGCTLMSR_BUS_LOCK_DETECT;



	if (vmx_get_perf_capabilities() & PMU_CAP_LBR_FMT)

		debugctl |= DEBUGCTLMSR_LBR_MASK;

arch/x86/kvm/vmx/vmx.c

+3 −0
Original line number Diff line number Diff line
@@ -2014,6 +2014,9 @@ static u64 vcpu_supported_debugctl(struct kvm_vcpu *vcpu) 
	if (!intel_pmu_lbr_is_enabled(vcpu))

		debugctl &= ~DEBUGCTLMSR_LBR_MASK;



	if (!guest_cpuid_has(vcpu, X86_FEATURE_BUS_LOCK_DETECT))

		debugctl &= ~DEBUGCTLMSR_BUS_LOCK_DETECT;



	return debugctl;

}