[PATCH 5/6] KVM: vmx/pmu: Add Arch LBR emulation and its VMCS field

Like Xu
2020-07-31T07:46:37Z

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@linux.intel.com>
---
arch/x86/include/asm/vmx.h | 2 ++
arch/x86/kvm/vmx/capabilities.h | 9 ++++++++-
arch/x86/kvm/vmx/pmu_intel.c | 17 ++++++++++++++---
arch/x86/kvm/vmx/vmx.c | 6 ++++--
4 files changed, 28 insertions(+), 6 deletions(-)

diff --git a/arch/x86/include/asm/vmx.h b/arch/x86/include/asm/vmx.h
index 27f53c81a17f..2e4b89a55c53 100644
--- a/arch/x86/include/asm/vmx.h
+++ b/arch/x86/include/asm/vmx.h
@@ -94,6 +94,7 @@
#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_ALWAYSON_WITHOUT_TRUE_MSR 0x00036dff

@@ -107,6 +108,7 @@
#define VM_ENTRY_LOAD_BNDCFGS 0x00010000
#define VM_ENTRY_PT_CONCEAL_PIP 0x00020000
#define VM_ENTRY_LOAD_IA32_RTIT_CTL 0x00040000
+#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 f5f0586f4cd7..d1f6bba243c4 100644
--- a/arch/x86/kvm/vmx/capabilities.h
+++ b/arch/x86/kvm/vmx/capabilities.h
@@ -378,6 +378,13 @@ static inline bool cpu_has_vmx_lbr(void)
(vmcs_config.vmentry_ctrl & VM_ENTRY_LOAD_DEBUG_CONTROLS);
}

+static inline bool cpu_has_vmx_arch_lbr(void)
+{
+ return boot_cpu_has(X86_FEATURE_ARCH_LBR) &&
+ (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)
{
/*
@@ -389,7 +396,7 @@ static inline u64 vmx_get_perf_capabilities(void)
if (boot_cpu_has(X86_FEATURE_PDCM))
rdmsrl(MSR_IA32_PERF_CAPABILITIES, perf_cap);

- if (cpu_has_vmx_lbr())
+ if (cpu_has_vmx_lbr() || cpu_has_vmx_arch_lbr())
perf_cap |= perf_cap & PMU_CAP_LBR_FMT;

return perf_cap;
diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
index 289c267732bd..daf838dc1689 100644
--- a/arch/x86/kvm/vmx/pmu_intel.c
+++ b/arch/x86/kvm/vmx/pmu_intel.c
@@ -177,12 +177,17 @@ bool intel_pmu_lbr_is_compatible(struct kvm_vcpu *vcpu)
if (pmu->version < 2)
return false;

+ 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.
*/
- if (boot_cpu_data.x86_model != guest_cpuid_model(vcpu))
+ if (!guest_cpuid_has(vcpu, X86_FEATURE_ARCH_LBR) &&
+ boot_cpu_data.x86_model != guest_cpuid_model(vcpu))
return false;

return !x86_perf_get_lbr(lbr);
@@ -210,8 +215,11 @@ 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)
@@ -693,6 +701,9 @@ static void vmx_update_intercept_for_lbr_msrs(struct kvm_vcpu *vcpu, bool set)
lbr->info + i, MSR_TYPE_RW, set);
}

+ if (guest_cpuid_has(vcpu, X86_FEATURE_ARCH_LBR))
+ return;
+
vmx_set_intercept_for_msr(msr_bitmap, MSR_LBR_SELECT, MSR_TYPE_RW, set);
vmx_set_intercept_for_msr(msr_bitmap, MSR_LBR_TOS, MSR_TYPE_RW, set);
}
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 9f42553b1e11..3843aebf4efb 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -2550,7 +2550,8 @@ static __init int setup_vmcs_config(struct vmcs_config *vmcs_conf,
VM_EXIT_LOAD_IA32_EFER |
VM_EXIT_CLEAR_BNDCFGS |
VM_EXIT_PT_CONCEAL_PIP |
- VM_EXIT_CLEAR_IA32_RTIT_CTL;
+ VM_EXIT_CLEAR_IA32_RTIT_CTL |
+ VM_EXIT_CLEAR_IA32_LBR_CTL;
if (adjust_vmx_controls(min, opt, MSR_IA32_VMX_EXIT_CTLS,
&_vmexit_control) < 0)
return -EIO;
@@ -2574,7 +2575,8 @@ static __init int setup_vmcs_config(struct vmcs_config *vmcs_conf,
VM_ENTRY_LOAD_IA32_EFER |
VM_ENTRY_LOAD_BNDCFGS |
VM_ENTRY_PT_CONCEAL_PIP |
- VM_ENTRY_LOAD_IA32_RTIT_CTL;
+ VM_ENTRY_LOAD_IA32_RTIT_CTL |
+ VM_ENTRY_LOAD_IA32_LBR_CTL;
if (adjust_vmx_controls(min, opt, MSR_IA32_VMX_ENTRY_CTLS,
&_vmentry_control) < 0)
return -EIO;
--
2.21.3