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=-2.1 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 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 094D0C1975A for ; Wed, 18 Mar 2020 02:07:20 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id C50A020724 for ; Wed, 18 Mar 2020 02:07:19 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="fgoNNKGo" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C50A020724 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:44292 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jEO74-0003N0-TX for qemu-devel@archiver.kernel.org; Tue, 17 Mar 2020 22:07:18 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:55746) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jEO6F-0002lL-UC for qemu-devel@nongnu.org; Tue, 17 Mar 2020 22:06:29 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1jEO6E-0006Id-28 for qemu-devel@nongnu.org; Tue, 17 Mar 2020 22:06:27 -0400 Received: from us-smtp-delivery-74.mimecast.com ([63.128.21.74]:59450) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1jEO6D-0006Bp-S6 for qemu-devel@nongnu.org; Tue, 17 Mar 2020 22:06:26 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1584497185; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=mLOFuo89Uh9yZ5HRef4Gqf26z9hOxh+13iUsI2C+jb4=; b=fgoNNKGo7rnLlpHGZdUesYE9PpDrCYSI3xzVkTzqbpl3ARxU7XKNcU/5gRVoJRufVeocmt hHEJfFSyBnBWQXtieH9vAE4R+uz3b4VupNlZjqJrwFU0QlCW/0mxmTKMChclC6P/pzMW6h yI16AsljpTyTTFUkdYOQ15HO6pwXfk8= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-312--B_xp1FOMg-x_6V4Q2COrg-1; Tue, 17 Mar 2020 22:06:21 -0400 X-MC-Unique: -B_xp1FOMg-x_6V4Q2COrg-1 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 mimecast-mx01.redhat.com (Postfix) with ESMTPS id 65CCF800D50; Wed, 18 Mar 2020 02:06:20 +0000 (UTC) Received: from [10.72.13.166] (ovpn-13-166.pek2.redhat.com [10.72.13.166]) by smtp.corp.redhat.com (Postfix) with ESMTP id B3B7919C58; Wed, 18 Mar 2020 02:06:09 +0000 (UTC) Subject: Re: [PATCH V2] vhost: correctly turn on VIRTIO_F_IOMMU_PLATFORM To: Peter Xu References: <20200226163618.31aa86ed.pasic@linux.ibm.com> <20200226115009-mutt-send-email-mst@kernel.org> <20200227140215.2d12149c.pasic@linux.ibm.com> <20200227104233-mutt-send-email-mst@kernel.org> <20200313134446.782c5f7c.pasic@linux.ibm.com> <20200313112902-mutt-send-email-mst@kernel.org> <20200313163122.GB95517@xz-x1> <20200316131723-mutt-send-email-mst@kernel.org> <20200316181405.GB184827@xz-x1> <158fbd3b-1285-e18d-b535-a1e7a9802f1f@redhat.com> <20200317141316.GA199571@xz-x1> From: Jason Wang Message-ID: Date: Wed, 18 Mar 2020 10:06:08 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: <20200317141316.GA199571@xz-x1> Content-Language: en-US X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: quoted-printable X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 63.128.21.74 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Tom Lendacky , "Singh, Brijesh" , "Michael S. Tsirkin" , qemu-devel@nongnu.org, qemu-stable@nongnu.org, Halil Pasic , Paolo Bonzini Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 2020/3/17 =E4=B8=8B=E5=8D=8810:13, Peter Xu wrote: > On Tue, Mar 17, 2020 at 11:04:26AM +0800, Jason Wang wrote: >> On 2020/3/17 =E4=B8=8A=E5=8D=882:14, Peter Xu wrote: >>> On Mon, Mar 16, 2020 at 01:19:54PM -0400, Michael S. Tsirkin wrote: >>>> On Fri, Mar 13, 2020 at 12:31:22PM -0400, Peter Xu wrote: >>>>> On Fri, Mar 13, 2020 at 11:29:59AM -0400, Michael S. Tsirkin wrote: >>>>>> On Fri, Mar 13, 2020 at 01:44:46PM +0100, Halil Pasic wrote: >>>>>>> [..] >>>>>>>>> CCing Tom. @Tom does vhost-vsock work for you with SEV and curren= t qemu? >>>>>>>>> >>>>>>>>> Also, one can specify iommu_platform=3Don on a device that ain't = a part of >>>>>>>>> a secure-capable VM, just for the fun of it. And that breaks >>>>>>>>> vhost-vsock. Or is setting iommu_platform=3Don only valid if >>>>>>>>> qemu-system-s390x is protected virtualization capable? >>>>>>>>> >>>>>>>>> BTW, I don't have a strong opinion on the fixes tag. We currently= do not >>>>>>>>> recommend setting iommu_platform, and thus I don't think we care = too >>>>>>>>> much about past qemus having problems with it. >>>>>>>>> >>>>>>>>> Regards, >>>>>>>>> Halil >>>>>>>> Let's just say if we do have a Fixes: tag we want to set it correc= tly to >>>>>>>> the commit that needs this fix. >>>>>>>> >>>>>>> I finally did some digging regarding the performance degradation. F= or >>>>>>> s390x the performance degradation on vhost-net was introduced by co= mmit >>>>>>> 076a93d797 ("exec: simplify address_space_get_iotlb_entry"). Before >>>>>>> IOMMUTLBEntry.addr_mask used to be based on plen, which in turn was >>>>>>> calculated as the rest of the memory regions size (from address), a= nd >>>>>>> covered most of the guest address space. That is we didn't have a w= hole >>>>>>> lot of IOTLB API overhead. >>>>>>> >>>>>>> With commit 076a93d797 I see IOMMUTLBEntry.addr_mask =3D=3D 0xfff w= hich comes >>>>>>> as ~TARGET_PAGE_MASK from flatview_do_translate(). To have things w= orking >>>>>>> properly I applied 75e5b70e6, b021d1c044, and d542800d1e on the lev= el of >>>>>>> 076a93d797 and 076a93d797~1. >>>>>> Peter, what's your take on this one? >>>>> Commit 076a93d797 was one of the patchset where we want to provide >>>>> sensible IOTLB entries and also that should start to work with huge >>>>> pages. >>>> So the issue bundamentally is that it >>>> never produces entries larger than page size. >>>> >>>> Wasteful even just with huge pages, all the more >>>> so which passthrough which could have giga-byte >>>> entries. >>>> >>>> Want to try fixing that? >>> Yes we can fix that, but I'm still not sure whether changing the >>> interface of address_space_get_iotlb_entry() to cover adhoc regions is >>> a good idea, because I think it's still a memory core API and imho it >>> would still be good to have IOTLBs returned to be what the hardware >>> will be using (always page aligned IOTLBs). Also it would still be >>> not ideal because vhost backend will still need to send the MISSING >>> messages and block for each of the continuous guest memory ranges >>> registered, so there will still be misterious delay. Not to say >>> logically all the caches can be invalidated too so in that sense I >>> think it's as hacky as the vhost speedup patch mentioned below.. >>> >>> Ideally I think vhost should be able to know when PT is enabled or >>> disabled for the device, so the vhost backend (kernel or userspace) >>> should be able to directly use GPA for DMA. That might need some new >>> vhost interface. >> Yes but I think we don't need another API since we can send GPA->HVA map= ping >> via device IOTLB API when we find there's no DMA translation at all (eit= her >> PT or no vIOMMU). > Jason, > > Do you mean what we've worked on before? > > https://lists.gnu.org/archive/html/qemu-devel/2017-06/msg00574.html > > (I just read the previous discussion on that patch, it seems to be > exactly what we've discussed again...) > > Thanks, Right, something like that. But it's not urgent now consider this patch=20 has been merged. Thanks >