patches/kernel/0011-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: Wed, 3 Aug 2022 18:50:03 +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 Also CR0.PG toggle when EFER.LMA is set, toggles the long 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/emulate.c | 14 +++++++++++++-
  19  1 file changed, 13 insertions(+), 1 deletion(-)
  20
  21 diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
  22 index f2a0a34f4687..874d124438d1 100644
  23 --- a/arch/x86/kvm/emulate.c
  24 +++ b/arch/x86/kvm/emulate.c
  25 @@ -3645,11 +3645,23 @@ static int em_movbe(struct x86_emulate_ctxt *ctxt)
  26
  27  static int em_cr_write(struct x86_emulate_ctxt *ctxt)
  28  {
  29 -       if (ctxt->ops->set_cr(ctxt, ctxt->modrm_reg, ctxt->src.val))
  30 +       int cr_num = ctxt->modrm_reg;
  31 +       int r;
  32 +
  33 +       if (ctxt->ops->set_cr(ctxt, cr_num, ctxt->src.val))
  34                 return emulate_gp(ctxt, 0);
  35
  36         /* Disable writeback. */
  37         ctxt->dst.type = OP_NONE;
  38 +
  39 +       if (cr_num == 0) {
  40 +               /* CR0 write might have updated CR0.PE and/or CR0.PG
  41 +                * which can affect the cpu execution mode */
  42 +               r = emulator_recalc_and_set_mode(ctxt);
  43 +               if (r != X86EMUL_CONTINUE)
  44 +                       return r;
  45 +       }
  46 +
  47         return X86EMUL_CONTINUE;
  48  }
  49