From: Zhang Chen <chen.zhang@xxxxxxxxx>
Allow guest to query if the underying VMM understands BHB-clearing
sequence and report the statue of BHB-clearing sequence in suprevisor
mode i.e. CPL < 3 via MSR_VIRTUAL_MITIGATION_ENUM/CTRL.
Enable BHI_DIS_S for guest if guest is using BHI-clearing sequence and
the sequence isn't effective on the processor.
Signed-off-by: Zhang Chen <chen.zhang@xxxxxxxxx>
Signed-off-by: Chao Gao <chao.gao@xxxxxxxxx>
Tested-by: Jiaan Lu <jiaan.lu@xxxxxxxxx>
---
arch/x86/kvm/vmx/vmx.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 25afb4c3e55e..abbbf8e66b53 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -1944,8 +1944,10 @@ static inline bool is_vmx_feature_control_msr_valid(struct vcpu_vmx *vmx,
}
#define VIRTUAL_ENUMERATION_VALID_BITS VIRT_ENUM_MITIGATION_CTRL_SUPPORT
-#define MITI_ENUM_VALID_BITS MITI_ENUM_RETPOLINE_S_SUPPORT
-#define MITI_CTRL_VALID_BITS MITI_CTRL_RETPOLINE_S_USED
+#define MITI_ENUM_VALID_BITS (MITI_ENUM_RETPOLINE_S_SUPPORT | \
+ MITI_ENUM_BHB_CLEAR_SEQ_S_SUPPORT)
+#define MITI_CTRL_VALID_BITS (MITI_CTRL_RETPOLINE_S_USED | \
+ MITI_CTRL_BHB_CLEAR_SEQ_S_USED)
static int vmx_get_msr_feature(struct kvm_msr_entry *msr)
{
@@ -2496,6 +2498,11 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
arch_msr & ARCH_CAP_RRSBA)
spec_ctrl_mask |= SPEC_CTRL_RRSBA_DIS_S;
+ if (data & MITI_CTRL_BHB_CLEAR_SEQ_S_USED &&
+ kvm_cpu_cap_has(X86_FEATURE_BHI_CTRL) &&
+ !(arch_msr & ARCH_CAP_BHI_NO))
+ spec_ctrl_mask |= SPEC_CTRL_BHI_DIS_S;
+
/*
* Intercept IA32_SPEC_CTRL to disallow guest from changing
* certain bits.
--
2.40.0
