[PATCH v3] KVM: nVMX: Sync L2 guest CET states between L1/L2

Yang Weijiang
2021-03-03T12:56:00Z

These fields are rarely updated by L1 QEMU/KVM, sync them when L1 is trying to
read/write them and after they're changed. If CET guest entry-load bit is not
set by L1 guest, migrate them to L2 manaully.

Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Yang Weijiang <weijiang.yang@intel.com>
---
arch/x86/kvm/cpuid.c | 1 -
arch/x86/kvm/vmx/nested.c | 30 ++++++++++++++++++++++++++++++
arch/x86/kvm/vmx/vmx.h | 3 +++
3 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index d191de769093..8692f53b8cd0 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -143,7 +143,6 @@ void kvm_update_cpuid_runtime(struct kvm_vcpu *vcpu)
}
vcpu->arch.guest_supported_xss =
(((u64)best->edx << 32) | best->ecx) & supported_xss;
-
} else {
vcpu->arch.guest_supported_xss = 0;
}
diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 9728efd529a1..24cace55e1f9 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -2516,6 +2516,13 @@ static void prepare_vmcs02_rare(struct vcpu_vmx *vmx, struct vmcs12 *vmcs12)
vmcs_write32(VM_ENTRY_MSR_LOAD_COUNT, vmx->msr_autoload.guest.nr);

set_cr4_guest_host_mask(vmx);
+
+ if (kvm_cet_supported() && vmx->nested.nested_run_pending &&
+ (vmcs12->vm_entry_controls & VM_ENTRY_LOAD_CET_STATE)) {
+ vmcs_writel(GUEST_SSP, vmcs12->guest_ssp);
+ vmcs_writel(GUEST_S_CET, vmcs12->guest_s_cet);
+ vmcs_writel(GUEST_INTR_SSP_TABLE, vmcs12->guest_ssp_tbl);
+ }
}

/*
@@ -2556,6 +2563,15 @@ static int prepare_vmcs02(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12,
if (kvm_mpx_supported() && (!vmx->nested.nested_run_pending ||
!(vmcs12->vm_entry_controls & VM_ENTRY_LOAD_BNDCFGS)))
vmcs_write64(GUEST_BNDCFGS, vmx->nested.vmcs01_guest_bndcfgs);
+
+ if (kvm_cet_supported() && (!vmx->nested.nested_run_pending ||
+ !(vmcs12->vm_entry_controls & VM_ENTRY_LOAD_CET_STATE))) {
+ vmcs_writel(GUEST_SSP, vmx->nested.vmcs01_guest_ssp);
+ vmcs_writel(GUEST_S_CET, vmx->nested.vmcs01_guest_s_cet);
+ vmcs_writel(GUEST_INTR_SSP_TABLE,
+ vmx->nested.vmcs01_guest_ssp_tbl);
+ }
+
vmx_set_rflags(vcpu, vmcs12->guest_rflags);

/* EXCEPTION_BITMAP and CR0_GUEST_HOST_MASK should basically be the
@@ -3375,6 +3391,12 @@ enum nvmx_vmentry_status nested_vmx_enter_non_root_mode(struct kvm_vcpu *vcpu,
if (kvm_mpx_supported() &&
!(vmcs12->vm_entry_controls & VM_ENTRY_LOAD_BNDCFGS))
vmx->nested.vmcs01_guest_bndcfgs = vmcs_read64(GUEST_BNDCFGS);
+ if (kvm_cet_supported() &&
+ !(vmcs12->vm_entry_controls & VM_ENTRY_LOAD_CET_STATE)) {
+ vmx->nested.vmcs01_guest_ssp = vmcs_readl(GUEST_SSP);
+ vmx->nested.vmcs01_guest_s_cet = vmcs_readl(GUEST_S_CET);
+ vmx->nested.vmcs01_guest_ssp_tbl = vmcs_readl(GUEST_INTR_SSP_TABLE);
+ }

/*
* Overwrite vmcs01.GUEST_CR3 with L1's CR3 if EPT is disabled *and*
@@ -4001,6 +4023,9 @@ static bool is_vmcs12_ext_field(unsigned long field)
case GUEST_IDTR_BASE:
case GUEST_PENDING_DBG_EXCEPTIONS:
case GUEST_BNDCFGS:
+ case GUEST_SSP:
+ case GUEST_INTR_SSP_TABLE:
+ case GUEST_S_CET:
return true;
default:
break;
@@ -4052,6 +4077,11 @@ static void sync_vmcs02_to_vmcs12_rare(struct kvm_vcpu *vcpu,
vmcs_readl(GUEST_PENDING_DBG_EXCEPTIONS);
if (kvm_mpx_supported())
vmcs12->guest_bndcfgs = vmcs_read64(GUEST_BNDCFGS);
+ if (kvm_cet_supported()) {
+ vmcs12->guest_ssp = vmcs_readl(GUEST_SSP);
+ vmcs12->guest_s_cet = vmcs_readl(GUEST_S_CET);
+ vmcs12->guest_ssp_tbl = vmcs_readl(GUEST_INTR_SSP_TABLE);
+ }

vmx->nested.need_sync_vmcs02_to_vmcs12_rare = false;
}
diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h
index 9d3a557949ac..36dc4fdb0909 100644
--- a/arch/x86/kvm/vmx/vmx.h
+++ b/arch/x86/kvm/vmx/vmx.h
@@ -155,6 +155,9 @@ struct nested_vmx {
/* to migrate it to L2 if VM_ENTRY_LOAD_DEBUG_CONTROLS is off */
u64 vmcs01_debugctl;
u64 vmcs01_guest_bndcfgs;
+ u64 vmcs01_guest_ssp;
+ u64 vmcs01_guest_s_cet;
+ u64 vmcs01_guest_ssp_tbl;

/* to migrate it to L1 if L2 writes to L1's CR8 directly */
int l1_tpr_threshold;
--
2.26.2