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=-15.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=ham 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 9F525C433E0 for ; Mon, 1 Feb 2021 03:13:34 +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 1F16C64E15 for ; Mon, 1 Feb 2021 03:13:34 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1F16C64E15 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=huawei.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:39814 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1l6Pef-00043n-0G for qemu-devel@archiver.kernel.org; Sun, 31 Jan 2021 22:13:33 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:56196) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1l6Pdm-0003VO-6M; Sun, 31 Jan 2021 22:12:38 -0500 Received: from szxga06-in.huawei.com ([45.249.212.32]:2604) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1l6Pdi-0007tw-AT; Sun, 31 Jan 2021 22:12:37 -0500 Received: from DGGEMS414-HUB.china.huawei.com (unknown [172.30.72.60]) by szxga06-in.huawei.com (SkyGuard) with ESMTP id 4DTXys5L03zjFs6; Mon, 1 Feb 2021 11:11:17 +0800 (CST) Received: from [10.174.184.214] (10.174.184.214) by DGGEMS414-HUB.china.huawei.com (10.3.19.214) with Microsoft SMTP Server id 14.3.498.0; Mon, 1 Feb 2021 11:12:12 +0800 Subject: Re: [RFC PATCH v2 3/3] vfio: Avoid disabling and enabling vectors repeatedly in VFIO migration To: Alex Williamson References: <20201209080919.156-1-lushenming@huawei.com> <20201209080919.156-4-lushenming@huawei.com> <20210126143614.175e271c@omen.home.shazbot.org> <7e61e7ae-e351-4228-d250-660251dcb0c0@huawei.com> <20210127072131.1c778247@x1.home.shazbot.org> From: Shenming Lu Message-ID: <2fc2db52-0677-c92e-f3c3-10fe9a77d75c@huawei.com> Date: Mon, 1 Feb 2021 11:12:12 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.2.2 MIME-Version: 1.0 In-Reply-To: <20210127072131.1c778247@x1.home.shazbot.org> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.184.214] X-CFilter-Loop: Reflected Received-SPF: pass client-ip=45.249.212.32; envelope-from=lushenming@huawei.com; helo=szxga06-in.huawei.com X-Spam_score_int: -42 X-Spam_score: -4.3 X-Spam_bar: ---- X-Spam_report: (-4.3 / 5.0 requ) BAYES_00=-1.9, NICE_REPLY_A=-0.079, RCVD_IN_DNSWL_MED=-2.3, RCVD_IN_MSPIKE_H4=-0.01, RCVD_IN_MSPIKE_WL=-0.01, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action 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: Lorenzo Pieralisi , Neo Jia , mst@redhat.com, Marc Zyngier , Cornelia Huck , "Dr . David Alan Gilbert" , qemu-devel@nongnu.org, Eric Auger , Kirti Wankhede , qemu-arm@nongnu.org, yuzenghui@huawei.com, wanghaibin.wang@huawei.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 2021/1/27 22:21, Alex Williamson wrote: > On Wed, 27 Jan 2021 19:27:35 +0800 > Shenming Lu wrote: > >> On 2021/1/27 5:36, Alex Williamson wrote: >>> On Wed, 9 Dec 2020 16:09:19 +0800 >>> Shenming Lu wrote: >>> >>>> Different from the normal situation when the guest starts, we can >>>> know the max unmasked vetctor (at the beginning) after msix_load() >>>> in VFIO migration. So in order to avoid ineffectively disabling and >>> >>> s/ineffectively/inefficiently/? It's "effective" either way I think. >> >> Yeah, I should say "inefficiently". :-) >> >>> >>>> enabling vectors repeatedly, let's allocate all needed vectors first >>>> and then enable these unmasked vectors one by one without disabling. >>>> >>>> Signed-off-by: Shenming Lu >>>> --- >>>> hw/pci/msix.c | 17 +++++++++++++++++ >>>> hw/vfio/pci.c | 10 ++++++++-- >>>> include/hw/pci/msix.h | 2 ++ >>>> 3 files changed, 27 insertions(+), 2 deletions(-) >>>> >>>> diff --git a/hw/pci/msix.c b/hw/pci/msix.c >>>> index 67e34f34d6..bf291d3ff8 100644 >>>> --- a/hw/pci/msix.c >>>> +++ b/hw/pci/msix.c >>>> @@ -557,6 +557,23 @@ unsigned int msix_nr_vectors_allocated(const PCIDevice *dev) >>>> return dev->msix_entries_nr; >>>> } >>>> >>>> +int msix_get_max_unmasked_vector(PCIDevice *dev) >>>> +{ >>>> + int max_unmasked_vector = -1; >>>> + int vector; >>>> + >>>> + if ((dev->config[dev->msix_cap + MSIX_CONTROL_OFFSET] & >>>> + (MSIX_ENABLE_MASK | MSIX_MASKALL_MASK)) == MSIX_ENABLE_MASK) { >>>> + for (vector = 0; vector < dev->msix_entries_nr; vector++) { >>>> + if (!msix_is_masked(dev, vector)) { >>>> + max_unmasked_vector = vector; >>>> + } >>>> + } >>>> + } >>>> + >>>> + return max_unmasked_vector; >>>> +} >>> >>> Comments from QEMU PCI folks? >>> >>>> + >>>> static int msix_set_notifier_for_vector(PCIDevice *dev, unsigned int vector) >>>> { >>>> MSIMessage msg; >>>> diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c >>>> index 51dc373695..e755ed2514 100644 >>>> --- a/hw/vfio/pci.c >>>> +++ b/hw/vfio/pci.c >>>> @@ -568,6 +568,9 @@ static void vfio_msix_vector_release(PCIDevice *pdev, unsigned int nr) >>>> >>>> static void vfio_msix_enable(VFIOPCIDevice *vdev) >>>> { >>>> + int max_unmasked_vector = msix_get_max_unmasked_vector(&vdev->pdev); >>>> + unsigned int used_vector = MAX(max_unmasked_vector, 0); >>>> + >>> >>> The above PCI function could also be done inline here pretty easily too: >>> >>> unsigned int nr, max_vec = 0; >>> >>> if (!msix_masked(&vdev->pdev)) >>> for (nr = 0; nr < msix_nr_vectors_allocated(&vdev->pdev); nr++) { >>> if (!msix_is_masked(&vdev->pdev, nr)) { >>> max_vec = nr; >>> } >>> } >>> } >>> >>> It's a bit cleaner than the msix utility function, imo. >> >> Yeah, it makes sense. >> >>> >>>> vfio_disable_interrupts(vdev); >>>> >>>> vdev->msi_vectors = g_new0(VFIOMSIVector, vdev->msix->entries); >>>> @@ -586,9 +589,12 @@ static void vfio_msix_enable(VFIOPCIDevice *vdev) >>>> * triggering to userspace, then immediately release the vector, leaving >>>> * the physical device with no vectors enabled, but MSI-X enabled, just >>>> * like the guest view. >>>> + * If there are unmasked vectors (such as in migration) which will be >>>> + * enabled soon, we can allocate them here to avoid ineffectively disabling >>>> + * and enabling vectors repeatedly later. >>> >>> It just happens that migration triggers this usage model where the >>> MSI-X enable bit is set with vectors unmasked in the vector table, but >>> this is not unique to migration, guests can follow this pattern as well. >>> Has this been tested with a variety of guests? Logically it seems >>> correct, but always good to prove so. Thanks, >> >> I have tested it in migration and normal guest startup (only the latest Linux). >> And I can try to test with some other kernels, could you be more specific about this? > > Minimally also Windows, ideally a BSD as well. Thanks, > Hi Alex, I have tested this patch with a Windows guest (Windows Server 2012 R2 Datacenter, Intel X722 Ethernet controller (passthrough)) and nothing went wrong. And I found that it does trigger our usage model in the normal guest startup: has all needed vectors already unmasked in the vector table when calling vfio_msix_enable()... Thanks, Shenming