When set bit 21 in vmentry_ctrl, VM entry will write the value from the
"Guest IA32_LBR_CTL" guest state field to IA32_LBR_CTL. When set bit 26
in vmexit_ctrl, VM exit will clear IA32_LBR_CTL after the value has been
saved to the "Guest IA32_LBR_CTL" guest state field.
To enable guest Arch LBR, KVM should set both the "Load Guest IA32_LBR_CTL"
entry control and the "Clear IA32_LBR_CTL" exit control. If these two
conditions cannot be met, the vmx_get_perf_capabilities() will clear
the LBR_FMT bits.
If Arch LBR is exposed on KVM, the guest could set X86_FEATURE_ARCH_LBR
to enable guest LBR, which is equivalent to the legacy LBR_FMT setting.
The Arch LBR feature could bypass the host/guest x86_model check and
the records msrs can still be pass-through to guest as usual and work
like the legacy LBR.
Signed-off-by: Like Xu <like.xu@xxxxxxxxxxxxxxx>
---
arch/x86/include/asm/vmx.h | 2 ++
arch/x86/kvm/vmx/capabilities.h | 25 +++++++++++++++++--------
arch/x86/kvm/vmx/pmu_intel.c | 17 ++++++++++++++---
arch/x86/kvm/vmx/vmx.c | 6 ++++--
4 files changed, 37 insertions(+), 13 deletions(-)
diff --git a/arch/x86/include/asm/vmx.h b/arch/x86/include/asm/vmx.h
index c099c3d17612..755179c0a5da 100644
--- a/arch/x86/include/asm/vmx.h
+++ b/arch/x86/include/asm/vmx.h
@@ -95,6 +95,7 @@
#define VM_EXIT_CLEAR_BNDCFGS 0x00800000
#define VM_EXIT_PT_CONCEAL_PIP 0x01000000
#define VM_EXIT_CLEAR_IA32_RTIT_CTL 0x02000000
+#define VM_EXIT_CLEAR_IA32_LBR_CTL 0x04000000
#define VM_EXIT_LOAD_CET_STATE 0x10000000
#define VM_EXIT_ALWAYSON_WITHOUT_TRUE_MSR 0x00036dff
@@ -110,6 +111,7 @@
#define VM_ENTRY_PT_CONCEAL_PIP 0x00020000
#define VM_ENTRY_LOAD_IA32_RTIT_CTL 0x00040000
#define VM_ENTRY_LOAD_CET_STATE 0x00100000
+#define VM_ENTRY_LOAD_IA32_LBR_CTL 0x00200000
#define VM_ENTRY_ALWAYSON_WITHOUT_TRUE_MSR 0x000011ff
diff --git a/arch/x86/kvm/vmx/capabilities.h b/arch/x86/kvm/vmx/capabilities.h
index 473c55c824b1..d84af64314fc 100644
--- a/arch/x86/kvm/vmx/capabilities.h
+++ b/arch/x86/kvm/vmx/capabilities.h
@@ -383,20 +383,29 @@ static inline bool vmx_pt_mode_is_host_guest(void)
return pt_mode == PT_MODE_HOST_GUEST;
}
-static inline u64 vmx_get_perf_capabilities(void)
+static inline bool cpu_has_vmx_arch_lbr(void)
{
- u64 perf_cap = 0;
-
- if (boot_cpu_has(X86_FEATURE_PDCM))
- rdmsrl(MSR_IA32_PERF_CAPABILITIES, perf_cap);
-
- perf_cap &= PMU_CAP_LBR_FMT;
+ return (vmcs_config.vmexit_ctrl & VM_EXIT_CLEAR_IA32_LBR_CTL) &&
+ (vmcs_config.vmentry_ctrl & VM_ENTRY_LOAD_IA32_LBR_CTL);
+}
+static inline u64 vmx_get_perf_capabilities(void)
+{
/*
* Since counters are virtualized, KVM would support full
* width counting unconditionally, even if the host lacks it.
*/
- return PMU_CAP_FW_WRITES | perf_cap;
+ u64 perf_cap = PMU_CAP_FW_WRITES;
+ u64 host_perf_cap = 0;
+
+ if (boot_cpu_has(X86_FEATURE_PDCM))
+ rdmsrl(MSR_IA32_PERF_CAPABILITIES, host_perf_cap);
+
+ perf_cap |= host_perf_cap & PMU_CAP_LBR_FMT;
+ if (boot_cpu_has(X86_FEATURE_ARCH_LBR) && !cpu_has_vmx_arch_lbr())
+ perf_cap &= ~PMU_CAP_LBR_FMT;
+
+ return perf_cap;
}
static inline u64 vmx_supported_debugctl(void)
diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
index a00d89c93eb7..7f20a8e75306 100644
--- a/arch/x86/kvm/vmx/pmu_intel.c
+++ b/arch/x86/kvm/vmx/pmu_intel.c
@@ -176,12 +176,17 @@ static inline struct kvm_pmc *get_fw_gp_pmc(struct kvm_pmu *pmu, u32 msr)
bool intel_pmu_lbr_is_compatible(struct kvm_vcpu *vcpu)
{
+ if (kvm_cpu_cap_has(X86_FEATURE_ARCH_LBR) !=
+ guest_cpuid_has(vcpu, X86_FEATURE_ARCH_LBR))
+ return false;
+
/*
* As a first step, a guest could only enable LBR feature if its
* cpu model is the same as the host because the LBR registers
* would be pass-through to the guest and they're model specific.
*/
- return boot_cpu_data.x86_model == guest_cpuid_model(vcpu);
+ return !guest_cpuid_has(vcpu, X86_FEATURE_ARCH_LBR) &&
+ boot_cpu_data.x86_model == guest_cpuid_model(vcpu);
}
bool intel_pmu_lbr_is_enabled(struct kvm_vcpu *vcpu)
@@ -199,8 +204,11 @@ static bool intel_pmu_is_valid_lbr_msr(struct kvm_vcpu *vcpu, u32 index)
if (!intel_pmu_lbr_is_enabled(vcpu))
return ret;
- ret = (index == MSR_LBR_SELECT) || (index == MSR_LBR_TOS) ||
- (index >= records->from && index < records->from + records->nr) ||
+ if (!guest_cpuid_has(vcpu, X86_FEATURE_ARCH_LBR))
+ ret = (index == MSR_LBR_SELECT) || (index == MSR_LBR_TOS);
+
+ if (!ret)
+ ret = (index >= records->from && index < records->from + records->nr) ||
(index >= records->to && index < records->to + records->nr);
if (!ret && records->info)
@@ -689,6 +697,9 @@ static void vmx_update_intercept_for_lbr_msrs(struct kvm_vcpu *vcpu, bool set)
vmx_set_intercept_for_msr(vcpu, lbr->info + i, MSR_TYPE_RW, set);
}
+ if (guest_cpuid_has(vcpu, X86_FEATURE_ARCH_LBR))
+ return;
+
vmx_set_intercept_for_msr(vcpu, MSR_LBR_SELECT, MSR_TYPE_RW, set);
vmx_set_intercept_for_msr(vcpu, MSR_LBR_TOS, MSR_TYPE_RW, set);
}
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index edecf2961924..9ddf0a14d75c 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -2632,7 +2632,8 @@ static __init int setup_vmcs_config(struct vmcs_config *vmcs_conf,
VM_EXIT_CLEAR_BNDCFGS |
VM_EXIT_PT_CONCEAL_PIP |
VM_EXIT_CLEAR_IA32_RTIT_CTL |
- VM_EXIT_LOAD_CET_STATE;
+ VM_EXIT_LOAD_CET_STATE |
+ VM_EXIT_CLEAR_IA32_LBR_CTL;
if (adjust_vmx_controls(min, opt, MSR_IA32_VMX_EXIT_CTLS,
&_vmexit_control) < 0)
return -EIO;
@@ -2657,7 +2658,8 @@ static __init int setup_vmcs_config(struct vmcs_config *vmcs_conf,
VM_ENTRY_LOAD_BNDCFGS |
VM_ENTRY_PT_CONCEAL_PIP |
VM_ENTRY_LOAD_IA32_RTIT_CTL |
- VM_ENTRY_LOAD_CET_STATE;
+ VM_ENTRY_LOAD_CET_STATE |
+ VM_ENTRY_LOAD_IA32_LBR_CTL;
if (adjust_vmx_controls(min, opt, MSR_IA32_VMX_ENTRY_CTLS,
&_vmentry_control) < 0)
return -EIO;
--
2.29.2
