KVM: X86: Expose bus lock debug exception to guest

mainline inclusion
from mainline-v5.13-rc2
commit 76ea438b
category: feature
feature: KVM Bus Lock Debug Exception
bugzilla: https://gitee.com/openeuler/intel-kernel/issues/I5RHW7
CVE: N/A
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/
commit/?id=76ea438b

Intel-SIG: commit 76ea438b ("KVM: X86: Expose bus lock debug exception to guest")

-------------------------------------

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: NXiaoyao Li <xiaoyao.li@intel.com>
Signed-off-by: NXiaoyao Li <xiaoyao.li@intel.com>
Signed-off-by: NChenyi Qiang <chenyi.qiang@intel.com>
Message-Id: <20210202090433.13441-4-chenyi.qiang@intel.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: NAichun Shi <aichun.shi@intel.com>

arch/x86/kvm/cpuid.c

@@ -441,7 +441,7 @@ 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

@@ -405,6 +405,9 @@ 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

@@ -2076,6 +2076,9 @@ 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;
 }