[PATCH v19 114/130] KVM: TDX: Handle MSR IA32_FEAT_CTL MSR and IA32_MCG_EXT_CTL

isaku.yamahata
2024-02-26T08:29:10Z

From: Isaku Yamahata <isaku.yamahata@intel.com>

MCE and MCA is advertised via cpuid based on the TDX module spec. Guest
kernel can access IA32_FEAT_CTL for checking if LMCE is enabled by platform
and IA32_MCG_EXT_CTL to enable LMCE. Make TDX KVM handle them. Otherwise
guest MSR access to them with TDG.VP.VMCALL<MSR> on VE results in GP in
guest.

Because LMCE is disabled with qemu by default, "-cpu lmce=on" to qemu
command line is needed to reproduce it.

Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
---
arch/x86/kvm/vmx/tdx.c | 20 ++++++++++++++++++++
1 file changed, 20 insertions(+)

diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
index 2bddaef495d1..3481c0b6ef2c 100644
--- a/arch/x86/kvm/vmx/tdx.c
+++ b/arch/x86/kvm/vmx/tdx.c
@@ -1952,6 +1952,7 @@ bool tdx_has_emulated_msr(u32 index, bool write)
default:
return true;
}
+ case MSR_IA32_FEAT_CTL:
case MSR_IA32_APICBASE:
case MSR_EFER:
return !write;
@@ -1966,6 +1967,20 @@ bool tdx_has_emulated_msr(u32 index, bool write)
int tdx_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr)
{
switch (msr->index) {
+ case MSR_IA32_FEAT_CTL:
+ /*
+ * MCE and MCA are advertised via cpuid. guest kernel could
+ * check if LMCE is enabled or not.
+ */
+ msr->data = FEAT_CTL_LOCKED;
+ if (vcpu->arch.mcg_cap & MCG_LMCE_P)
+ msr->data |= FEAT_CTL_LMCE_ENABLED;
+ return 0;
+ case MSR_IA32_MCG_EXT_CTL:
+ if (!msr->host_initiated && !(vcpu->arch.mcg_cap & MCG_LMCE_P))
+ return 1;
+ msr->data = vcpu->arch.mcg_ext_ctl;
+ return 0;
case MSR_MTRRcap:
/*
* Override kvm_mtrr_get_msr() which hardcodes the value.
@@ -1984,6 +1999,11 @@ int tdx_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr)
int tdx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr)
{
switch (msr->index) {
+ case MSR_IA32_MCG_EXT_CTL:
+ if (!msr->host_initiated && !(vcpu->arch.mcg_cap & MCG_LMCE_P))
+ return 1;
+ vcpu->arch.mcg_ext_ctl = msr->data;
+ return 0;
case MSR_MTRRdefType:
/*
* Allow writeback only for all memory.
--
2.25.1