[RFC PATCH v4 5/8] KVM:VMX: Load Guest CET via VMCS when CET is enabled in Guest

From: Yang Weijiang
Date: Tue Mar 19 2019 - 04:12:42 EST


"Load Guest CET state" bit controls whether guest CET states
will be loaded at Guest entry. Before doing that, KVM needs
to check if CPU CET feature is available.

Signed-off-by: Zhang Yi Z <yi.z.zhang@xxxxxxxxxxxxxxx>
Signed-off-by: Yang Weijiang <weijiang.yang@xxxxxxxxx>
---
arch/x86/kvm/vmx.c | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 28b8ac027bd7..246467c12930 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -55,6 +55,7 @@
#include <asm/mmu_context.h>
#include <asm/spec-ctrl.h>
#include <asm/mshyperv.h>
+#include <asm/cet.h>

#include "trace.h"
#include "pmu.h"
@@ -5414,6 +5415,23 @@ static int vmx_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
return 1;
}

+ /*
+ * To enable Guest CET, check whether CPU CET feature is
+ * available, if it's there, set Guest CET state loading bit
+ * per CR4.CET status, otherwise, return a fault to Guest.
+ */
+ if (guest_cpuid_has(vcpu, X86_FEATURE_SHSTK) ||
+ guest_cpuid_has(vcpu, X86_FEATURE_IBT)) {
+ if (cr4 & X86_CR4_CET)
+ vmcs_set_bits(VM_ENTRY_CONTROLS,
+ VM_ENTRY_LOAD_GUEST_CET_STATE);
+ else
+ vmcs_clear_bits(VM_ENTRY_CONTROLS,
+ VM_ENTRY_LOAD_GUEST_CET_STATE);
+ } else if (cr4 & X86_CR4_CET) {
+ return 1;
+ }
+
if (to_vmx(vcpu)->nested.vmxon && !nested_cr4_valid(vcpu, cr4))
return 1;

--
2.17.1