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| author | Paolo Bonzini <pbonzini@redhat.com> | 2013-10-31 23:05:24 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2013-11-29 11:11:49 -0800 |
| commit | b5f92a134b69faeffa0e1a811f01a48d686a4e97 (patch) | |
| tree | 3b32913921851e428b2f199d06bf3a87922e06b1 /arch/x86/kvm | |
| parent | b4673c4343e86c0b74d79e8b02eafa0da263989a (diff) | |
| download | lwn-b5f92a134b69faeffa0e1a811f01a48d686a4e97.tar.gz lwn-b5f92a134b69faeffa0e1a811f01a48d686a4e97.zip | |
KVM: x86: fix emulation of "movzbl %bpl, %eax"
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>
Diffstat (limited to 'arch/x86/kvm')
| -rw-r--r-- | arch/x86/kvm/emulate.c | 5 |
1 files changed, 4 insertions, 1 deletions
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c index 5953dcea752d..5484d54582ca 100644 --- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -4207,7 +4207,10 @@ static int decode_operand(struct x86_emulate_ctxt *ctxt, struct operand *op, 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; |