patches/kernel/0018-KVM-x86-SVM-don-t-save-SVM-state-to-SMRAM-when-VM-is.patch

   1 From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
   2 From: Maxim Levitsky <mlevitsk@redhat.com>
   3 Date: Wed, 3 Aug 2022 18:50:10 +0300
   4 Subject: [PATCH] KVM: x86: SVM: don't save SVM state to SMRAM when VM is not
   5  long mode capable
   6
   7 When the guest CPUID doesn't have support for long mode, 32 bit SMRAM
   8 layout is used and it has no support for preserving EFER and/or SVM
   9 state.
  10
  11 Note that this isn't relevant to running 32 bit guests on VM which is
  12 long mode capable - such VM can still run 32 bit guests in compatibility
  13 mode.
  14
  15 Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
  16 Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
  17 ---
  18  arch/x86/kvm/svm/svm.c | 9 +++++++++
  19  1 file changed, 9 insertions(+)
  20
  21 diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
  22 index 23ad430207c5..69ebe1dca33d 100644
  23 --- a/arch/x86/kvm/svm/svm.c
  24 +++ b/arch/x86/kvm/svm/svm.c
  25 @@ -4308,6 +4308,15 @@ static int svm_enter_smm(struct kvm_vcpu *vcpu, union kvm_smram *smram)
  26         if (!is_guest_mode(vcpu))
  27                 return 0;
  28
  29 +       /*
  30 +        * 32 bit SMRAM format doesn't preserve EFER and SVM state.
  31 +        * SVM should not be enabled by the userspace without marking
  32 +        * the CPU as at least long mode capable.
  33 +        */
  34 +
  35 +       if (!guest_cpuid_has(vcpu, X86_FEATURE_LM))
  36 +               return 1;
  37 +
  38         smram->smram64.svm_guest_flag = 1;
  39         smram->smram64.svm_guest_vmcb_gpa = svm->nested.vmcb12_gpa;
  40