On 02/11/2014 10:54, Nadav Amit wrote:
> Commit 7fe864dc942c ("KVM: x86: Emulator considers imm as memory operand")
> marked VEX instructions as such in protected mode. VEX-prefix instructions are
> not supported relevant on real-mode and VM86, but should cause #UD instead of
> being decoded as LES/LDS.
>
> Fix this behaviour to be consistent with real hardware.
>
> Signed-off-by: Nadav Amit <namit@xxxxxxxxxxxxxxxxx>
> ---
> arch/x86/kvm/emulate.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
> index db8cb4d6..24b0df7 100644
> --- a/arch/x86/kvm/emulate.c
> +++ b/arch/x86/kvm/emulate.c
> @@ -4505,8 +4505,7 @@ done_prefixes:
>
> /* vex-prefix instructions are not implemented */
> if (ctxt->opcode_len == 1 && (ctxt->b == 0xc5 || ctxt->b == 0xc4) &&
> - (mode == X86EMUL_MODE_PROT64 ||
> - (mode >= X86EMUL_MODE_PROT16 && (ctxt->modrm & 0x80)))) {
> + (mode == X86EMUL_MODE_PROT64 || (ctxt->modrm & 0x80))) {
This should also check for (ctxt->modrm & 0xc0) == 0xc0 instead of just
ctxt->modrm & 0x80. Otherwise, installation of Windows XP and 2003 is
broken on pre-Westmere system, because they execute LDS in the process
of transitioning from 16- to 32-bit protected mode.
This was not visible before because at this point CS is already 32-bit;
I fixed the patch.
Paolo
> ctxt->d = NotImpl;
> }
>
>
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