Allow guest to query if the underying VMM understands Retpoline and
report the statue of Retpoline in suprevisor mode i.e. CPL < 3 via
MSR_VIRTUAL_MITIGATION_ENUM/CTRL.
Disable RRSBA behavior by setting RRSBA_DIS_S for guest if guest is
using retpoline and the processor has the behavior.
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 | 24 +++++++++++++++++++++---
1 file changed, 21 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 980498c4c30c..25afb4c3e55e 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -1944,8 +1944,8 @@ 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 0ULL
-#define MITI_CTRL_VALID_BITS 0ULL
+#define MITI_ENUM_VALID_BITS MITI_ENUM_RETPOLINE_S_SUPPORT
+#define MITI_CTRL_VALID_BITS MITI_CTRL_RETPOLINE_S_USED
static int vmx_get_msr_feature(struct kvm_msr_entry *msr)
{
@@ -2173,7 +2173,7 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
struct vmx_uret_msr *msr;
int ret = 0;
u32 msr_index = msr_info->index;
- u64 data = msr_info->data, spec_ctrl_mask;
+ u64 data = msr_info->data, arch_msr = 0, spec_ctrl_mask = 0;
u32 index;
switch (msr_index) {
@@ -2488,6 +2488,24 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
if (data & ~MITI_CTRL_VALID_BITS)
return 1;
+ if (boot_cpu_has(X86_FEATURE_ARCH_CAPABILITIES))
+ rdmsrl(MSR_IA32_ARCH_CAPABILITIES, arch_msr);
+
+ if (data & MITI_CTRL_RETPOLINE_S_USED &&
+ kvm_cpu_cap_has(X86_FEATURE_RRSBA_CTRL) &&
+ arch_msr & ARCH_CAP_RRSBA)
+ spec_ctrl_mask |= SPEC_CTRL_RRSBA_DIS_S;
+
+ /*
+ * Intercept IA32_SPEC_CTRL to disallow guest from changing
+ * certain bits.
+ */
+ if (spec_ctrl_mask && !cpu_has_spec_ctrl_virt())
+ vmx_enable_intercept_for_msr(vcpu, MSR_IA32_SPEC_CTRL, MSR_TYPE_RW);
+
+ vmx_set_spec_ctrl_mask(vmx, spec_ctrl_mask);
+ vmx_set_guest_spec_ctrl(vmx, vmx_get_guest_spec_ctrl(vmx));
+
vmx->msr_virtual_mitigation_ctrl = data;
break;
default:
--
2.40.0
