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Subject[PATCH v3 12/13] KVM: x86: SVM: don't save SVM state to SMRAM when VM is not long mode capable
Date
When the guest CPUID doesn't have support for long mode, 32 bit SMRAM
layout is used and it has no support for preserving EFER and/or SVM
state.

Note that this isn't relevant to running 32 bit guests on VM which is
long mode capable - such VM can still run 32 bit guests in compatibility
mode.

Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
---
arch/x86/kvm/svm/svm.c | 9 +++++++++
1 file changed, 9 insertions(+)

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 7ca5e06878e19a..64cfd26bc5e7a6 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -4442,6 +4442,15 @@ static int svm_enter_smm(struct kvm_vcpu *vcpu, union kvm_smram *smram)
if (!is_guest_mode(vcpu))
return 0;

+ /*
+ * 32 bit SMRAM format doesn't preserve EFER and SVM state.
+ * SVM should not be enabled by the userspace without marking
+ * the CPU as at least long mode capable.
+ */
+
+ if (!guest_cpuid_has(vcpu, X86_FEATURE_LM))
+ return 1;
+
smram->smram64.svm_guest_flag = 1;
smram->smram64.svm_guest_vmcb_gpa = svm->nested.vmcb12_gpa;

--
2.26.3
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