From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8B6B6C3A589 for ; Thu, 15 Aug 2019 18:16:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 68A062064A for ; Thu, 15 Aug 2019 18:16:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732378AbfHOSQI (ORCPT ); Thu, 15 Aug 2019 14:16:08 -0400 Received: from mx1.redhat.com ([209.132.183.28]:57446 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726001AbfHOSQI (ORCPT ); Thu, 15 Aug 2019 14:16:08 -0400 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id DFA9DC057E9F; Thu, 15 Aug 2019 18:16:07 +0000 (UTC) Received: from x1.home (ovpn-116-99.phx2.redhat.com [10.3.116.99]) by smtp.corp.redhat.com (Postfix) with ESMTP id 79B5D43FD5; Thu, 15 Aug 2019 18:16:07 +0000 (UTC) Date: Thu, 15 Aug 2019 12:16:07 -0600 From: Alex Williamson To: Sean Christopherson Cc: Paolo Bonzini , Radim =?UTF-8?B?S3LEjW3DocWZ?= , kvm@vger.kernel.org, Xiao Guangrong Subject: Re: [PATCH v2 11/27] KVM: x86/mmu: Zap only the relevant pages when removing a memslot Message-ID: <20190815121607.29055aa2@x1.home> In-Reply-To: <20190815160006.GC27076@linux.intel.com> References: <20190205205443.1059-1-sean.j.christopherson@intel.com> <20190205210137.1377-11-sean.j.christopherson@intel.com> <20190813100458.70b7d82d@x1.home> <20190813170440.GC13991@linux.intel.com> <20190813115737.5db7d815@x1.home> <20190813133316.6fc6f257@x1.home> <20190813201914.GI13991@linux.intel.com> <20190815092324.46bb3ac1@x1.home> <20190815160006.GC27076@linux.intel.com> Organization: Red Hat MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.32]); Thu, 15 Aug 2019 18:16:08 +0000 (UTC) Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Thu, 15 Aug 2019 09:00:06 -0700 Sean Christopherson wrote: > On Thu, Aug 15, 2019 at 09:23:24AM -0600, Alex Williamson wrote: > > Ok, fun day of trying to figure out which ranges are relevant, I've > > narrowed it down to all of these: > > > > 0xffe00 > > 0xfee00 > > 0xfec00 > > APIC and I/O APIC stuff > > > 0xc1000 > > Assigned audio > > > 0x80a000 > > ? > > > 0x800000 > > GPU BAR > > > 0x100000 > > ? > > The APIC ranges are puzzling, I wouldn't expect their mappings to change. > > > ie. I can effective only say that sp->gfn values of 0x0, 0x40000, and > > 0x80000 can take the continue branch without seeing bad behavior in the > > VM. > > > > The assigned GPU has BARs at GPAs: > > > > 0xc0000000-0xc0ffffff > > 0x800000000-0x808000000 > > 0x808000000-0x809ffffff > > > > And the assigned companion audio function is at GPA: > > > > 0xc1080000-0xc1083fff > > > > Only one of those seems to align very well with a gfn base involved > > here. The virtio ethernet has an mmio range at GPA 0x80a000000, > > otherwise I don't find any other I/O devices coincident with the gfns > > above. > > > > I'm running the VM with 2MB hugepages, but I believe the issue still > > occurs with standard pages. When run with standard pages I see more > > hits to gfn values 0, 0x40000, 0x80000, but the same number of hits to > > the set above that cannot take the continue branch. I don't know if > > that means anything. > > > > Any further ideas what to look for? Thanks, > > Maybe try isolating which memslot removal causes problems? E.g. flush > the affected ranges if base_gfn == (xxx || yyy || zzz), otherwise flush > only the memslot's gfns. Based on the log you sent a while back for gfn > mismatches, I'm guessing the culprits are all GPU BARs, but it's > probably worth confirming. That might also explain why gfn == 0x80000 > can take the continue branch, i.e. if removing the corresponding memslot > is what's causing problems, then it's being flushed and not actually > taking the continue path. If I print out the memslot base_gfn, it seems pretty evident that only the assigned device mappings are triggering this branch. The base_gfns exclusively include: 0x800000 0x808000 0xc0089 Where the first two clearly match the 64bit BARs and the last is the result of a page that we need to emulate within the BAR @0xc0000000 at offset 0x88000, so the base_gfn is the remaining direct mapping. I don't know if this implies we're doing something wrong for assigned device slots, but maybe a more targeted workaround would be if we could specifically identify these slots, though there's no special registration of them versus other slots. Did you have any non-device assignment test cases that took this branch when developing the series? > One other thought would be to force a call to kvm_flush_remote_tlbs(kvm), > e.g. set flush=true just before the final kvm_mmu_remote_flush_or_zap(). > Maybe it's a case where there are no SPTEs for the memslot, but the TLB > flush is needed for some reason. This doesn't work. Thanks, Alex