From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755174AbaHAMVg (ORCPT ); Fri, 1 Aug 2014 08:21:36 -0400 Received: from mx1.redhat.com ([209.132.183.28]:52393 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754881AbaHAMVf (ORCPT ); Fri, 1 Aug 2014 08:21:35 -0400 From: Vitaly Kuznetsov To: David Vrabel Cc: , Konrad Rzeszutek Wilk , Boris Ostrovsky , Stefano Stabellini , Andrew Jones , Subject: Re: [PATCH RFC 0/4] xen/pvhvm: fix shared_info and pirq issues with kexec References: <1405431640-649-1-git-send-email-vkuznets@redhat.com> <53D64F07.1070106@citrix.com> Date: Fri, 01 Aug 2014 14:21:20 +0200 In-Reply-To: <53D64F07.1070106@citrix.com> (David Vrabel's message of "Mon, 28 Jul 2014 14:24:23 +0100") Message-ID: <87k36s9z9b.fsf@vitty.brq.redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.3 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org David Vrabel writes: > On 15/07/14 14:40, Vitaly Kuznetsov wrote: >> With this patch series I'm trying to address several issues with kexec on pvhvm: >> - shared_info issue (1st patch, just sending Olaf's work with Konrad's fix) >> - create specific pvhvm shutdown handler for kexec (2nd patch) >> - GSI PIRQ issue (3rd patch, I'm pretty confident that it does the right thing) >> - MSI PIRQ issue (4th patch, and I'm not sure it doesn't break anything -> RFC) >> >> This patch series can be tested on single vCPU guest. We still have SMP issues with >> pvhvm guests and kexec which require additional fixes. > > In addition to the fixes for multi-VCPU guests, what else remains? > I'm aware of grants and ballooned out pages. > What's the plan for handling granted pages? > (if I got the design right) we have two issues: 1) Pages we grant access to other domains. We have the list so we can try doing gnttab_end_foreign_access for all unmapped grants but there is nothing we can do with mapped ones from guest. We can either assume that all such usages are short-term and try waiting for them to finish or we need to do something like force-unmap from hypervisor side. 2) Pages we mapped from other domains. There is no easy way to collect all grant handles from different places in kernel atm so I can see two possible solutions: - we keep track of all handles with new kernel structure in guest and unmap them all on kexec/kdump. - we introduce new GNTTABOP_reset which does something similar to gnttab_release_mappings(). There is nothing we need to do with transferred grants (and I don't see transfer usages in kernel). Please correct me if I'm wrong. > I don't think we want to accept a partial solution unless the known > non-working configurations fail fast on kexec load. *I think* we can leave ballooned out pages out of scope for now. Thanks, > > David -- Vitaly