| From daf727225b8abfdfe424716abac3d15a3ac5626a Mon Sep 17 00:00:00 2001 |
| From: Paolo Bonzini <pbonzini@redhat.com> |
| Date: Thu, 31 Oct 2013 23:05:24 +0100 |
| Subject: KVM: x86: fix emulation of "movzbl %bpl, %eax" |
| |
| From: Paolo Bonzini <pbonzini@redhat.com> |
| |
| commit daf727225b8abfdfe424716abac3d15a3ac5626a upstream. |
| |
| When I was looking at RHEL5.9's failure to start with |
| unrestricted_guest=0/emulate_invalid_guest_state=1, I got it working with a |
| slightly older tree than kvm.git. I now debugged the remaining failure, |
| which was introduced by commit 660696d1 (KVM: X86 emulator: fix |
| source operand decoding for 8bit mov[zs]x instructions, 2013-04-24) |
| introduced a similar mis-emulation to the one in commit 8acb4207 (KVM: |
| fix sil/dil/bpl/spl in the mod/rm fields, 2013-05-30). The incorrect |
| decoding occurs in 8-bit movzx/movsx instructions whose 8-bit operand |
| is sil/dil/bpl/spl. |
| |
| Needless to say, "movzbl %bpl, %eax" does occur in RHEL5.9's decompression |
| prolog, just a handful of instructions before finally giving control to |
| the decompressed vmlinux and getting out of the invalid guest state. |
| |
| Because OpMem8 bypasses decode_modrm, the same handling of the REX prefix |
| must be applied to OpMem8. |
| |
| Reported-by: Michele Baldessari <michele@redhat.com> |
| Cc: Gleb Natapov <gleb@redhat.com> |
| Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> |
| Signed-off-by: Gleb Natapov <gleb@redhat.com> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| arch/x86/kvm/emulate.c | 5 ++++- |
| 1 file changed, 4 insertions(+), 1 deletion(-) |
| |
| --- a/arch/x86/kvm/emulate.c |
| +++ b/arch/x86/kvm/emulate.c |
| @@ -4207,7 +4207,10 @@ static int decode_operand(struct x86_emu |
| case OpMem8: |
| ctxt->memop.bytes = 1; |
| if (ctxt->memop.type == OP_REG) { |
| - ctxt->memop.addr.reg = decode_register(ctxt, ctxt->modrm_rm, 1); |
| + int highbyte_regs = ctxt->rex_prefix == 0; |
| + |
| + ctxt->memop.addr.reg = decode_register(ctxt, ctxt->modrm_rm, |
| + highbyte_regs); |
| fetch_register_operand(&ctxt->memop); |
| } |
| goto mem_common; |