Re: [Xen-devel] [PATCH] x86: don't clear high 32 bits of RAX on sub-word guest I/O port reads

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 08/05/15 13:08, Jan Beulich wrote:
> 1- or 2-byte operations never alter the high halves of registers.
>
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

>
> --- a/xen/arch/x86/traps.c
> +++ b/xen/arch/x86/traps.c
> @@ -2234,7 +2234,7 @@ static int emulate_privileged_op(struct 
>              if ( op_bytes == 4 )
>                  regs->eax = 0;
>              else
> -                regs->eax &= ~((1u << (op_bytes * 8)) - 1);
> +                regs->eax &= ~((1 << (op_bytes * 8)) - 1);
>              regs->eax |= guest_io_read(port, op_bytes, v, regs);
>          }
>          bpmatch = check_guest_io_breakpoint(v, port, op_bytes);
>
>
>


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