From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-yh0-f47.google.com (mail-yh0-f47.google.com [209.85.213.47]) by kanga.kvack.org (Postfix) with ESMTP id 6C41A6B0038 for ; Tue, 16 Jun 2015 10:33:26 -0400 (EDT) Received: by yhid80 with SMTP id d80so12565664yhi.1 for ; Tue, 16 Jun 2015 07:33:26 -0700 (PDT) Received: from SMTP02.CITRIX.COM (smtp02.citrix.com. [66.165.176.63]) by mx.google.com with ESMTPS id m46si376560yhb.99.2015.06.16.07.33.24 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Tue, 16 Jun 2015 07:33:25 -0700 (PDT) Message-ID: <5580326D.30006@citrix.com> Date: Tue, 16 Jun 2015 15:27:57 +0100 From: David Vrabel MIME-Version: 1.0 Subject: Re: [PATCH 07/12] x86/virt/guest/xen: Remove use of pgd_list from the Xen guest code References: <1434188955-31397-1-git-send-email-mingo@kernel.org> <1434188955-31397-8-git-send-email-mingo@kernel.org> <1434359109.13744.14.camel@hellion.org.uk> <557EA944.9020504@citrix.com> <20150615203532.GC13273@gmail.com> <55802F94.90306@citrix.com> <5580307F.8050007@oracle.com> In-Reply-To: <5580307F.8050007@oracle.com> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Boris Ostrovsky , Ingo Molnar Cc: Ian Campbell , Konrad Rzeszutek Wilk , linux-kernel@vger.kernel.org, linux-mm@kvack.org, xen-devel@lists.xenproject.org, Andy Lutomirski , Andrew Morton , Denys Vlasenko , Brian Gerst , Peter Zijlstra , Borislav Petkov , "H. Peter Anvin" , Linus Torvalds , Oleg Nesterov , Thomas Gleixner , Waiman Long On 16/06/15 15:19, Boris Ostrovsky wrote: > On 06/16/2015 10:15 AM, David Vrabel wrote: >> On 15/06/15 21:35, Ingo Molnar wrote: >>> * David Vrabel wrote: >>> >>>> On 15/06/15 10:05, Ian Campbell wrote: >>>>> On Sat, 2015-06-13 at 11:49 +0200, Ingo Molnar wrote: >>>>>> xen_mm_pin_all()/unpin_all() are used to implement full guest >>>>>> instance >>>>>> suspend/restore. It's a stop-all method that needs to iterate >>>>>> through all >>>>>> allocated pgds in the system to fix them up for Xen's use. >>>>>> >>>>>> This code uses pgd_list, probably because it was an easy interface. >>>>>> >>>>>> But we want to remove the pgd_list, so convert the code over to >>>>>> walk all >>>>>> tasks in the system. This is an equivalent method. >>>> It is not equivalent because pgd_alloc() now populates entries in >>>> pgds that are >>>> not visible to xen_mm_pin_all() (note how the original code adds the >>>> pgd to the >>>> pgd_list in pgd_ctor() before calling pgd_prepopulate_pmd()). These >>>> newly >>>> allocated page tables won't be correctly converted on suspend/resume >>>> and the new >>>> process will die after resume. >>> So how should the Xen logic be fixed for the new scheme? I can't say >>> I can see >>> through the paravirt complexity here. >> Actually, since we freeze_processes() before trying to pin page tables, >> I think it should be ok as-is. >> >> I'll put the patch through some tests. > > Actually, I just ran this through a couple of boot/suspend/resume tests > and didn't see any issues (with the one fix I mentioned to Ingo > earlier). On unstable Xen only. In which case this can have a: Reviewed-by: David Vrabel Thanks. David -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org