[PATCH v3 6/9] KVM: vmx/pmu: Add MSR_ARCH_LBR_CTL emulation for Arch LBR

Like Xu
2021-03-03T18:11:48Z

Arch LBRs are enabled by setting MSR_ARCH_LBR_CTL.LBREn to 1. A new guest
state field named "Guest IA32_LBR_CTL" is added to enhance guest LBR usage.
When guest Arch LBR is enabled, a guest LBR event will be created like the
model-specific LBR does.

On processors that support Arch LBR, MSR_IA32_DEBUGCTLMSR[bit 0] has no
meaning. It can be written to 0 or 1, but reads will always return 0. On
the vmx_vcpu_reset(), the IA32_LBR_CTL will be cleared to 0.

Signed-off-by: Like Xu <like.xu@linux.intel.com>
---
arch/x86/include/asm/vmx.h | 2 ++
arch/x86/kvm/vmx/pmu_intel.c | 27 ++++++++++++++++++++++-----
arch/x86/kvm/vmx/vmx.c | 9 +++++++++
3 files changed, 33 insertions(+), 5 deletions(-)

diff --git a/arch/x86/include/asm/vmx.h b/arch/x86/include/asm/vmx.h
index 358707f60d99..8ec7bc24b37a 100644
--- a/arch/x86/include/asm/vmx.h
+++ b/arch/x86/include/asm/vmx.h
@@ -245,6 +245,8 @@ enum vmcs_field {
GUEST_BNDCFGS_HIGH = 0x00002813,
GUEST_IA32_RTIT_CTL = 0x00002814,
GUEST_IA32_RTIT_CTL_HIGH = 0x00002815,
+ GUEST_IA32_LBR_CTL = 0x00002816,
+ GUEST_IA32_LBR_CTL_HIGH = 0x00002817,
HOST_IA32_PAT = 0x00002c00,
HOST_IA32_PAT_HIGH = 0x00002c01,
HOST_IA32_EFER = 0x00002c02,
diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
index 25d620685ae7..d14a14eb712d 100644
--- a/arch/x86/kvm/vmx/pmu_intel.c
+++ b/arch/x86/kvm/vmx/pmu_intel.c
@@ -19,6 +19,7 @@
#include "pmu.h"

#define MSR_PMC_FULL_WIDTH_BIT (MSR_IA32_PMC0 - MSR_IA32_PERFCTR0)
+#define KVM_ARCH_LBR_CTL_MASK 0x7f000f

static struct kvm_event_hw_type_mapping intel_arch_events[] = {
/* Index must match CPUID 0x0A.EBX bit vector */
@@ -221,6 +222,7 @@ static bool intel_is_valid_msr(struct kvm_vcpu *vcpu, u32 msr)
ret = pmu->version > 1;
break;
case MSR_ARCH_LBR_DEPTH:
+ case MSR_ARCH_LBR_CTL:
ret = guest_cpuid_has(vcpu, X86_FEATURE_ARCH_LBR);
break;
default:
@@ -390,6 +392,9 @@ static int intel_pmu_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
case MSR_ARCH_LBR_DEPTH:
msr_info->data = lbr_desc->records.nr;
return 0;
+ case MSR_ARCH_LBR_CTL:
+ msr_info->data = vmcs_read64(GUEST_IA32_LBR_CTL);
+ return 0;
default:
if ((pmc = get_gp_pmc(pmu, msr, MSR_IA32_PERFCTR0)) ||
(pmc = get_gp_pmc(pmu, msr, MSR_IA32_PMC0))) {
@@ -457,6 +462,15 @@ static int intel_pmu_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
lbr_desc->records.nr = data;
lbr_desc->arch_lbr_reset = true;
return 0;
+ case MSR_ARCH_LBR_CTL:
+ if (!(data & ~KVM_ARCH_LBR_CTL_MASK)) {
+ vmcs_write64(GUEST_IA32_LBR_CTL, data);
+ if (intel_pmu_lbr_is_enabled(vcpu) && !lbr_desc->event &&
+ (data & ARCH_LBR_CTL_LBREN))
+ intel_pmu_create_guest_lbr_event(vcpu);
+ return 0;
+ }
+ break;
default:
if ((pmc = get_gp_pmc(pmu, msr, MSR_IA32_PERFCTR0)) ||
(pmc = get_gp_pmc(pmu, msr, MSR_IA32_PMC0))) {
@@ -635,12 +649,15 @@ static void intel_pmu_reset(struct kvm_vcpu *vcpu)
*/
static void intel_pmu_legacy_freezing_lbrs_on_pmi(struct kvm_vcpu *vcpu)
{
- u64 data = vmcs_read64(GUEST_IA32_DEBUGCTL);
+ u32 lbr_ctl_field = GUEST_IA32_DEBUGCTL;

- if (data & DEBUGCTLMSR_FREEZE_LBRS_ON_PMI) {
- data &= ~DEBUGCTLMSR_LBR;
- vmcs_write64(GUEST_IA32_DEBUGCTL, data);
- }
+ if (!(vmcs_read64(GUEST_IA32_DEBUGCTL) & DEBUGCTLMSR_FREEZE_LBRS_ON_PMI))
+ return;
+
+ if (guest_cpuid_has(vcpu, X86_FEATURE_ARCH_LBR))
+ lbr_ctl_field = GUEST_IA32_LBR_CTL;
+
+ vmcs_write64(lbr_ctl_field, vmcs_read64(lbr_ctl_field) & ~BIT(0));
}

static void intel_pmu_deliver_pmi(struct kvm_vcpu *vcpu)
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 6d7e760fdfa0..a0660b9934c6 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -2036,6 +2036,13 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
VM_EXIT_SAVE_DEBUG_CONTROLS)
get_vmcs12(vcpu)->guest_ia32_debugctl = data;

+ /*
+ * For Arch LBR, IA32_DEBUGCTL[bit 0] has no meaning.
+ * It can be written to 0 or 1, but reads will always return 0.
+ */
+ if (guest_cpuid_has(vcpu, X86_FEATURE_ARCH_LBR))
+ data &= ~DEBUGCTLMSR_LBR;
+
vmcs_write64(GUEST_IA32_DEBUGCTL, data);
if (intel_pmu_lbr_is_enabled(vcpu) && !to_vmx(vcpu)->lbr_desc.event &&
(data & DEBUGCTLMSR_LBR))
@@ -4463,6 +4470,8 @@ static void vmx_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
vmcs_writel(GUEST_SYSENTER_ESP, 0);
vmcs_writel(GUEST_SYSENTER_EIP, 0);
vmcs_write64(GUEST_IA32_DEBUGCTL, 0);
+ if (cpu_has_vmx_arch_lbr())
+ vmcs_write64(GUEST_IA32_LBR_CTL, 0);
}

kvm_set_rflags(vcpu, X86_EFLAGS_FIXED);
--
2.29.2