From mboxrd@z Thu Jan 1 00:00:00 1970 From: =?windows-1252?Q?Roger_Pau_Monn=E9?= Subject: Re: [PATCH v3 3/3] xen: rework paging_log_dirty_op to work with hvm guests Date: Wed, 6 May 2015 14:32:42 +0200 Message-ID: <554A09EA.3060706@citrix.com> References: <1428686959-2890-1-git-send-email-roger.pau@citrix.com> <1428686959-2890-4-git-send-email-roger.pau@citrix.com> <552D20D70200007800071E38@mail.emea.novell.com> <554A0123.9030408@citrix.com> <554A20BB02000078000771E4@mail.emea.novell.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail6.bemta5.messagelabs.com ([195.245.231.135]) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1YpyVb-0002GF-KT for xen-devel@lists.xenproject.org; Wed, 06 May 2015 12:33:03 +0000 In-Reply-To: <554A20BB02000078000771E4@mail.emea.novell.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Jan Beulich Cc: Andrew Cooper , Tim Deegan , xen-devel@lists.xenproject.org List-Id: xen-devel@lists.xenproject.org El 06/05/15 a les 14.10, Jan Beulich ha escrit: >>>> On 06.05.15 at 13:55, wrote: >> El 14/04/15 a les 14.14, Jan Beulich ha escrit: >>>>>> On 10.04.15 at 19:29, wrote: >>>> + BUG_ON(((pages >> 3) % PAGE_SIZE) + bytes > PAGE_SIZE); >>> >>> I don't seem to be able to spot the original for this one. If there >>> was none, please make this an ASSERT() instead. >> >> Yes, there's no previous BUG_ON because this was not a problem in the >> past, since we could write to any position on dirty_bitmap, but that's >> not the case any more. Since we only have one page mapped at a time we >> need to make sure that what we are about to write doesn't cross a page >> boundary. >> >> I understand this is not an ideal solution, but AFAICT there's no easy >> way to deal with writes that expand over a page boundary. > > I'm afraid I don't really see what you're asking for. Just to clarify - > I didn't put anything under question, all I asked for was to use > ASSERT() instead of BUG_ON() here. Yet what you wrote above > doesn't seem to related to that request. I don't think an ASSERT is appropriate here, because it means that on non-debug versions we might write past the end of the mapped page without noticing. Roger.