Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756506AbbFPOQf (ORCPT ); Tue, 16 Jun 2015 10:16:35 -0400 Received: from smtp.citrix.com ([66.165.176.89]:61797 "EHLO SMTP.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754942AbbFPOQW (ORCPT ); Tue, 16 Jun 2015 10:16:22 -0400 X-IronPort-AV: E=Sophos;i="5.13,626,1427760000"; d="scan'208";a="272438537" Message-ID: <55802F94.90306@citrix.com> Date: Tue, 16 Jun 2015 15:15:48 +0100 From: David Vrabel User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Icedove/31.4.0 MIME-Version: 1.0 To: Ingo Molnar CC: Ian Campbell , Konrad Rzeszutek Wilk , Boris Ostrovsky , , , , Andy Lutomirski , Andrew Morton , Denys Vlasenko , Brian Gerst , Peter Zijlstra , Borislav Petkov , "H. Peter Anvin" , Linus Torvalds , "Oleg Nesterov" , Thomas Gleixner , Waiman Long 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 X-DLP: MIA2 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1526 Lines: 36 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 from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/