From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Jan Beulich" Subject: Re: trap bounce flags Date: Wed, 25 Apr 2007 12:11:01 +0100 Message-ID: <462F5365.76E4.0078.0@novell.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: Content-Disposition: inline List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Keir Fraser Cc: xen-devel@lists.xensource.com List-Id: xen-devel@lists.xenproject.org >>> Keir Fraser 25.04.07 12:56 >>> >On 25/4/07 11:41, "Keir Fraser" wrote: > >> Attached is my own proposed patch which I think cleans up all the = issues. >> Checking just flags in asm and keeping the null-bounce check in >> init_int80_direct_trap() seems fine to me. > >The change of a movw $0 to a movb $TBF_EXCEPTION in that patch is wrong, = by >the way. Should be movb $0. Which means there's not really a dependency on this being non-zero... The patch looks otherwise okay to me, though I think there's one more issue here: There's another suffix-less instruction (updating UREGS_rip in int80_slow_path) - this must be a subq, and it must imply that no = 32-bit guest places an int $0x80 at 0xfffffffe. And my patch has a not directly related adjustment removing the movl $TRAP_syscall,UREGS_entry_vector+8(%rsp) close to the end of compat_create_bounce_frame, as this is meaningless here. Jan