patches/kernel/0014-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 MIME-Version: 1.0
   7 Content-Type: text/plain; charset=UTF-8
   8 Content-Transfer-Encoding: 8bit
   9
  10 When the guest CPUID doesn't have support for long mode, 32 bit SMRAM
  11 layout is used and it has no support for preserving EFER and/or SVM
  12 state.
  13
  14 Note that this isn't relevant to running 32 bit guests on VM which is
  15 long mode capable - such VM can still run 32 bit guests in compatibility
  16 mode.
  17
  18 Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
  19 Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
  20 Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>
  21 ---
  22  arch/x86/kvm/svm/svm.c | 9 +++++++++
  23  1 file changed, 9 insertions(+)
  24
  25 diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
  26 index 023b6507a539..a7acbe8246b6 100644
  27 --- a/arch/x86/kvm/svm/svm.c
  28 +++ b/arch/x86/kvm/svm/svm.c
  29 @@ -4400,6 +4400,15 @@ static int svm_enter_smm(struct kvm_vcpu *vcpu, union kvm_smram *smram)
  30         if (!is_guest_mode(vcpu))
  31                 return 0;
  32
  33 +       /*
  34 +        * 32 bit SMRAM format doesn't preserve EFER and SVM state.
  35 +        * SVM should not be enabled by the userspace without marking
  36 +        * the CPU as at least long mode capable.
  37 +        */
  38 +
  39 +       if (!guest_cpuid_has(vcpu, X86_FEATURE_LM))
  40 +               return 1;
  41 +
  42         smram->smram64.svm_guest_flag = 1;
  43         smram->smram64.svm_guest_vmcb_gpa = svm->nested.vmcb12_gpa;
  44