From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:41256) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZluiE-0001Wo-56 for qemu-devel@nongnu.org; Tue, 13 Oct 2015 04:13:34 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Zlui9-0007Rh-4t for qemu-devel@nongnu.org; Tue, 13 Oct 2015 04:13:34 -0400 Received: from mail-vk0-f53.google.com ([209.85.213.53]:34245) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Zlui9-0007Rc-1Z for qemu-devel@nongnu.org; Tue, 13 Oct 2015 04:13:29 -0400 Received: by vkat63 with SMTP id t63so5708662vka.1 for ; Tue, 13 Oct 2015 01:13:28 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <561C4CA4.9010506@twiddle.net> References: <1444211031-11624-1-git-send-email-rth@twiddle.net> <1444211031-11624-5-git-send-email-rth@twiddle.net> <5617C252.6070104@gmail.com> <561C4CA4.9010506@twiddle.net> From: Peter Maydell Date: Tue, 13 Oct 2015 09:13:08 +0100 Message-ID: Content-Type: text/plain; charset=UTF-8 Subject: Re: [Qemu-devel] [PULL 04/26] target-*: Introduce and use cpu_breakpoint_test List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Richard Henderson Cc: Sergey Fedorov , QEMU Developers On 13 October 2015 at 01:13, Richard Henderson wrote: > Why do you believe that a zero-length TB won't be cleared? > The TB still has a start address, which is contained within > a given page, which is invalidated. > > Some target-*/translate.c takes care to advance the PC, but I believe that > this is only required when the breakpoint instruction *itself* could span a > page boundary. I.e. the TB needs to be marked to span two pages. This > situation can never be true for many RISC targets. If this is the reason for the logic it would be good to have a comment explaining it in the code. I've never really understood that part... -- PMM