patches/kernel/0024-KVM-x86-emulator-update-the-emulation-mode-after-CR0.patch

   1 From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
   2 From: Maxim Levitsky <mlevitsk@redhat.com>
   3 Date: Tue, 21 Jun 2022 18:08:56 +0300
   4 Subject: [PATCH] KVM: x86: emulator: update the emulation mode after CR0 write
   5
   6 CR0.PE toggles real/protected mode, thus its update
   7 should update the emulation mode.
   8
   9 This is likely a benign bug because there is no writeback
  10 of state, other than the RIP increment, and when toggling
  11 CR0.PE, the CPU has to execute code from a very low memory address.
  12
  13 Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
  14 Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
  15 ---
  16  arch/x86/kvm/emulate.c | 13 ++++++++++++-
  17  1 file changed, 12 insertions(+), 1 deletion(-)
  18
  19 diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
  20 index 03a761397599..76c407167449 100644
  21 --- a/arch/x86/kvm/emulate.c
  22 +++ b/arch/x86/kvm/emulate.c
  23 @@ -3647,11 +3647,22 @@ static int em_movbe(struct x86_emulate_ctxt *ctxt)
  24
  25  static int em_cr_write(struct x86_emulate_ctxt *ctxt)
  26  {
  27 -       if (ctxt->ops->set_cr(ctxt, ctxt->modrm_reg, ctxt->src.val))
  28 +       int cr_num = ctxt->modrm_reg;
  29 +       int r;
  30 +
  31 +       if (ctxt->ops->set_cr(ctxt, cr_num, ctxt->src.val))
  32                 return emulate_gp(ctxt, 0);
  33
  34         /* Disable writeback. */
  35         ctxt->dst.type = OP_NONE;
  36 +
  37 +       if (cr_num == 0) {
  38 +               /* CR0 write might have updated CR0.PE */
  39 +               r = update_emulation_mode(ctxt);
  40 +               if (r != X86EMUL_CONTINUE)
  41 +                       return r;
  42 +       }
  43 +
  44         return X86EMUL_CONTINUE;
  45  }
  46