2014-10-03 01:10+0300, Nadav Amit:
> Once an instruction crosses a page boundary, the size read from the second
> page
> disregards the common case that part of the operand resides on the first page.
> As a result, fetch of long insturctions may fail, and thereby cause the
> decoding to fail as well.
>
> Signed-off-by: Nadav Amit <na...@cs.technion.ac.il>
> ---
Good catch, was it thanks to an exhaustive test-suite?
Reviewed-by: Radim Krčmář <rkrc...@redhat.com>
> arch/x86/kvm/emulate.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
> index 694dfa7..b2e8aba 100644
> --- a/arch/x86/kvm/emulate.c
> +++ b/arch/x86/kvm/emulate.c
> @@ -751,8 +751,10 @@ static int __do_insn_fetch_bytes(struct x86_emulate_ctxt
> *ctxt, int op_size)
> static __always_inline int do_insn_fetch_bytes(struct x86_emulate_ctxt *ctxt,
> unsigned size)
> {
> - if (unlikely(ctxt->fetch.end - ctxt->fetch.ptr < size))
> - return __do_insn_fetch_bytes(ctxt, size);
> + unsigned done_size = ctxt->fetch.end - ctxt->fetch.ptr;
> +
> + if (unlikely(done_size < size))
> + return __do_insn_fetch_bytes(ctxt, size - done_size);
> else
> return X86EMUL_CONTINUE;
> }
> --
> 1.9.1
>
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