[PATCH v4 16/17] kvm: x86: Add support IA32_CORE_CAPABILITY MSR

[Fenghua Yu]

From: Xiaoyao Li <xiaoyao.li@xxxxxxxxxxxxxxx>

MSR IA32_CORE_CAPABILITY is a feature-enumerating MSR, bit 5 of which
reports the capability of enabling detection of split locks (will be
supported on future processors based on Tremont microarchitecture and
later).

Please check the latest Intel Architecture Instruction Set Extensions
and Future Features Programming Reference for more detailed information
on the MSR and the split lock bit.

1. Expose it to user space as a feature-enumerating MSR, so that user
space can query it.

2. Emualte MSR_IA32_CORE_CAPABILITY with vmx->core_capability. And add the
get and set handler of MSR_IA32_CORE_CAPABILITY.
   For uesrspace, it can set this MSR when customizing features of guest,
also it can read the value of this MSR of guest.
   For guest, as it's a feature-enumerating MSR, guest only can read it.

Signed-off-by: Xiaoyao Li <xiaoyao.li@xxxxxxxxxxxxxxx>
Signed-off-by: Fenghua Yu <fenghua.yu@xxxxxxxxx>
---
 arch/x86/include/asm/kvm_host.h |  1 +
 arch/x86/kvm/vmx/vmx.c          | 23 +++++++++++++++++++++++
 arch/x86/kvm/vmx/vmx.h          |  1 +
 arch/x86/kvm/x86.c              | 17 ++++++++++++++++-
 4 files changed, 41 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 180373360e34..208f15570d17 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1527,6 +1527,7 @@ int kvm_pv_send_ipi(struct kvm *kvm, unsigned long ipi_bitmap_low,
 		    unsigned long icr, int op_64_bit);
 
 u64 kvm_get_arch_capabilities(void);
+u64 kvm_get_core_capability(void);
 void kvm_define_shared_msr(unsigned index, u32 msr);
 int kvm_set_shared_msr(unsigned index, u64 val, u64 mask);
 
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 30a6bcd735ec..3e03c6e1e558 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -1679,6 +1679,12 @@ static int vmx_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 
 		msr_info->data = to_vmx(vcpu)->spec_ctrl;
 		break;
+	case MSR_IA32_CORE_CAPABILITY:
+		if (!msr_info->host_initiated &&
+		    !guest_cpuid_has(vcpu, X86_FEATURE_CORE_CAPABILITY))
+			return 1;
+		msr_info->data = vmx->core_capability;
+		break;
 	case MSR_IA32_ARCH_CAPABILITIES:
 		if (!msr_info->host_initiated &&
 		    !guest_cpuid_has(vcpu, X86_FEATURE_ARCH_CAPABILITIES))
@@ -1891,6 +1897,21 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 		vmx_disable_intercept_for_msr(vmx->vmcs01.msr_bitmap, MSR_IA32_PRED_CMD,
 					      MSR_TYPE_W);
 		break;
+	case MSR_IA32_CORE_CAPABILITY:
+		if (!msr_info->host_initiated)
+			return 1;
+		if (data & ~CORE_CAP_SPLIT_LOCK_DETECT)
+			return 1;
+
+		/*
+		 * Since AC split lock is a hardware feature, and there is no
+		 * software emulation yet, we cannot enable it for guest if
+		 * host hardware doesn't support it.
+		 */
+		if (!boot_cpu_has(X86_FEATURE_SPLIT_LOCK_DETECT))
+			data &= ~CORE_CAP_SPLIT_LOCK_DETECT;
+		vmx->core_capability = data;
+		break;
 	case MSR_IA32_ARCH_CAPABILITIES:
 		if (!msr_info->host_initiated)
 			return 1;
@@ -4083,6 +4104,8 @@ static void vmx_vcpu_setup(struct vcpu_vmx *vmx)
 		++vmx->nmsrs;
 	}
 
+	vmx->core_capability = kvm_get_core_capability();
+
 	vmx->arch_capabilities = kvm_get_arch_capabilities();
 
 	vm_exit_controls_init(vmx, vmx_vmexit_ctrl());
diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h
index 0ac0a64c7790..cc22379991f3 100644
--- a/arch/x86/kvm/vmx/vmx.h
+++ b/arch/x86/kvm/vmx/vmx.h
@@ -191,6 +191,7 @@ struct vcpu_vmx {
 	u64		      msr_guest_kernel_gs_base;
 #endif
 
+	u64		      core_capability;
 	u64		      arch_capabilities;
 	u64		      spec_ctrl;
 
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 941f932373d0..c3c9e3f2d08a 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1125,7 +1125,8 @@ static u32 msrs_to_save[] = {
 #endif
 	MSR_IA32_TSC, MSR_IA32_CR_PAT, MSR_VM_HSAVE_PA,
 	MSR_IA32_FEATURE_CONTROL, MSR_IA32_BNDCFGS, MSR_TSC_AUX,
-	MSR_IA32_SPEC_CTRL, MSR_IA32_ARCH_CAPABILITIES,
+	MSR_IA32_SPEC_CTRL, MSR_IA32_CORE_CAPABILITY,
+	MSR_IA32_ARCH_CAPABILITIES,
 	MSR_IA32_RTIT_CTL, MSR_IA32_RTIT_STATUS, MSR_IA32_RTIT_CR3_MATCH,
 	MSR_IA32_RTIT_OUTPUT_BASE, MSR_IA32_RTIT_OUTPUT_MASK,
 	MSR_IA32_RTIT_ADDR0_A, MSR_IA32_RTIT_ADDR0_B,
@@ -1197,11 +1198,22 @@ static u32 msr_based_features[] = {
 
 	MSR_F10H_DECFG,
 	MSR_IA32_UCODE_REV,
+	MSR_IA32_CORE_CAPABILITY,
 	MSR_IA32_ARCH_CAPABILITIES,
 };
 
 static unsigned int num_msr_based_features;
 
+u64 kvm_get_core_capability(void)
+{
+	u64 data;
+
+	rdmsrl_safe(MSR_IA32_CORE_CAPABILITY, &data);
+
+	return data;
+}
+EXPORT_SYMBOL_GPL(kvm_get_core_capability);
+
 u64 kvm_get_arch_capabilities(void)
 {
 	u64 data;
@@ -1227,6 +1239,9 @@ EXPORT_SYMBOL_GPL(kvm_get_arch_capabilities);
 static int kvm_get_msr_feature(struct kvm_msr_entry *msr)
 {
 	switch (msr->index) {
+	case MSR_IA32_CORE_CAPABILITY:
+		msr->data = kvm_get_core_capability();
+		break;
 	case MSR_IA32_ARCH_CAPABILITIES:
 		msr->data = kvm_get_arch_capabilities();
 		break;
-- 
2.7.4