From mboxrd@z Thu Jan  1 00:00:00 1970
From: Andrew Cooper <andrew.cooper3@citrix.com>
Subject: Re: [PATCH] x86: don't clear high 32 bits of RAX on
 sub-word guest I/O port reads
Date: Fri, 8 May 2015 13:36:51 +0100
Message-ID: <554CADE3.2020601@citrix.com>
References: <554CC34502000078000783A3@mail.emea.novell.com>
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To: Jan Beulich <JBeulich@suse.com>, xen-devel <xen-devel@lists.xenproject.org>
Cc: Keir Fraser <keir@xen.org>
List-Id: xen-devel@lists.xenproject.org

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@suse.com>

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

>
> --- 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);
>
>
>