[PATCH v2 1/3] KVM: nSVM: restore the L1 host state prior to resuming a nested guest on SMM exit

Maxim Levitsky
2021-08-23T11:46:51Z

If the guest is entered prior to restoring the host save area,
the guest entry code might see incorrect L1 state (e.g paging state).

Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
---
arch/x86/kvm/svm/svm.c | 23 +++++++++++++----------
1 file changed, 13 insertions(+), 10 deletions(-)

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 1a70e11f0487..ea7a4dacd42f 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -4347,27 +4347,30 @@ static int svm_leave_smm(struct kvm_vcpu *vcpu, const char *smstate)
gpa_to_gfn(vmcb12_gpa), &map) == -EINVAL)
return 1;

- if (svm_allocate_nested(svm))
+ if (kvm_vcpu_map(vcpu, gpa_to_gfn(svm->nested.hsave_msr),
+ &map_save) == -EINVAL)
return 1;

- vmcb12 = map.hva;
-
- nested_load_control_from_vmcb12(svm, &vmcb12->control);
-
- ret = enter_svm_guest_mode(vcpu, vmcb12_gpa, vmcb12);
- kvm_vcpu_unmap(vcpu, &map, true);
+ if (svm_allocate_nested(svm))
+ return 1;

/*
* Restore L1 host state from L1 HSAVE area as VMCB01 was
* used during SMM (see svm_enter_smm())
*/
- if (kvm_vcpu_map(vcpu, gpa_to_gfn(svm->nested.hsave_msr),
- &map_save) == -EINVAL)
- return 1;

svm_copy_vmrun_state(&svm->vmcb01.ptr->save,
map_save.hva + 0x400);

+ /*
+ * Restore L2 state
+ */
+
+ vmcb12 = map.hva;
+ nested_load_control_from_vmcb12(svm, &vmcb12->control);
+ ret = enter_svm_guest_mode(vcpu, vmcb12_gpa, vmcb12);
+
+ kvm_vcpu_unmap(vcpu, &map, true);
kvm_vcpu_unmap(vcpu, &map_save, true);
}
}
--
2.26.3