54 lines
2.0 KiB
Diff
54 lines
2.0 KiB
Diff
Bugzilla: 967652
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Upstream-status: 3.13 (should hit stable)
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From daf727225b8abfdfe424716abac3d15a3ac5626a Mon Sep 17 00:00:00 2001
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From: Paolo Bonzini <pbonzini@redhat.com>
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Date: Thu, 31 Oct 2013 23:05:24 +0100
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Subject: [PATCH] KVM: x86: fix emulation of "movzbl %bpl, %eax"
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When I was looking at RHEL5.9's failure to start with
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unrestricted_guest=0/emulate_invalid_guest_state=1, I got it working with a
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slightly older tree than kvm.git. I now debugged the remaining failure,
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which was introduced by commit 660696d1 (KVM: X86 emulator: fix
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source operand decoding for 8bit mov[zs]x instructions, 2013-04-24)
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introduced a similar mis-emulation to the one in commit 8acb4207 (KVM:
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fix sil/dil/bpl/spl in the mod/rm fields, 2013-05-30). The incorrect
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decoding occurs in 8-bit movzx/movsx instructions whose 8-bit operand
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is sil/dil/bpl/spl.
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Needless to say, "movzbl %bpl, %eax" does occur in RHEL5.9's decompression
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prolog, just a handful of instructions before finally giving control to
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the decompressed vmlinux and getting out of the invalid guest state.
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Because OpMem8 bypasses decode_modrm, the same handling of the REX prefix
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must be applied to OpMem8.
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Reported-by: Michele Baldessari <michele@redhat.com>
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Cc: stable@vger.kernel.org
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Cc: Gleb Natapov <gleb@redhat.com>
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Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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Signed-off-by: Gleb Natapov <gleb@redhat.com>
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---
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arch/x86/kvm/emulate.c | 5 ++++-
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1 file changed, 4 insertions(+), 1 deletion(-)
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diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
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index 16c037e..282d28c 100644
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--- a/arch/x86/kvm/emulate.c
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+++ b/arch/x86/kvm/emulate.c
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@@ -4117,7 +4117,10 @@ static int decode_operand(struct x86_emulate_ctxt *ctxt, struct operand *op,
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case OpMem8:
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ctxt->memop.bytes = 1;
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if (ctxt->memop.type == OP_REG) {
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- ctxt->memop.addr.reg = decode_register(ctxt, ctxt->modrm_rm, 1);
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+ int highbyte_regs = ctxt->rex_prefix == 0;
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+
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+ ctxt->memop.addr.reg = decode_register(ctxt, ctxt->modrm_rm,
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+ highbyte_regs);
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fetch_register_operand(&ctxt->memop);
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}
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goto mem_common;
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--
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1.8.3.1
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