Explicitly truncate the data written to vmcs.SYSENTER_EIP/ESP on WRMSR
if the virtual CPU doesn't support 64-bit mode. The SYSENTER address
fields in the VMCS are natural width, i.e. bits 63:32 are dropped if the
CPU doesn't support Intel 64 architectures. This behavior is visible to
the guest after a VM-Exit/VM-Exit roundtrip, e.g. if the guest sets bits
63:32 in the actual MSR.
Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
---
arch/x86/kvm/vmx/vmx.c | 18 ++++++++++++++++--
1 file changed, 16 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 3ab6ca6062ce..bc91ce499a7a 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -1936,6 +1936,16 @@ static int vmx_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
return 0;
}
+static u64 nested_vmx_truncate_sysenter_addr(struct kvm_vcpu *vcpu,
+ u64 data)
+{
+#ifdef CONFIG_X86_64
+ if (!guest_cpuid_has(vcpu, X86_FEATURE_LM))
+ return (u32)data;
+#endif
+ return (unsigned long)data;
+}
+
/*
* Writes msr value into the appropriate "register".
* Returns 0 on success, non-0 otherwise.
@@ -1973,13 +1983,17 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
vmcs_write32(GUEST_SYSENTER_CS, data);
break;
case MSR_IA32_SYSENTER_EIP:
- if (is_guest_mode(vcpu))
+ if (is_guest_mode(vcpu)) {
+ data = nested_vmx_truncate_sysenter_addr(vcpu, data);
get_vmcs12(vcpu)->guest_sysenter_eip = data;
+ }
vmcs_writel(GUEST_SYSENTER_EIP, data);
break;
case MSR_IA32_SYSENTER_ESP:
- if (is_guest_mode(vcpu))
+ if (is_guest_mode(vcpu)) {
+ data = nested_vmx_truncate_sysenter_addr(vcpu, data);
get_vmcs12(vcpu)->guest_sysenter_esp = data;
+ }
vmcs_writel(GUEST_SYSENTER_ESP, data);
break;
case MSR_IA32_DEBUGCTLMSR:
--
2.26.0
