From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-yk0-f171.google.com (mail-yk0-f171.google.com [209.85.160.171]) by kanga.kvack.org (Postfix) with ESMTP id E9CD86B0038 for ; Tue, 16 Jun 2015 10:16:23 -0400 (EDT) Received: by ykfr66 with SMTP id r66so14397461ykf.0 for ; Tue, 16 Jun 2015 07:16:23 -0700 (PDT) Received: from SMTP.CITRIX.COM (smtp.citrix.com. [66.165.176.89]) by mx.google.com with ESMTPS id e3si357310ywf.121.2015.06.16.07.16.22 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Tue, 16 Jun 2015 07:16:23 -0700 (PDT) Message-ID: <55802F94.90306@citrix.com> Date: Tue, 16 Jun 2015 15:15:48 +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> In-Reply-To: <20150615203532.GC13273@gmail.com> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Ingo Molnar Cc: Ian Campbell , Konrad Rzeszutek Wilk , Boris Ostrovsky , 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 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. 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