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=-13.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable 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 201D8C4361B for ; Tue, 15 Dec 2020 00:17:55 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (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 A9802221EF for ; Tue, 15 Dec 2020 00:17:54 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A9802221EF Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To:Message-ID: Subject:To:From:Date:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=aHEmcunw2QwovZC1z2oskhpjIh5aC3ZXgGdPCfNAJnE=; b=wiRZ3+/dCRssi6n1bwQUL9u56 u1NCxiN5/f6UJmeXIne4ZtDSiDEgUgAskWDQPnCMYc4Eli6/KrVm7Xiq38p2tmMXYrv0cZFVvOmI9 BvS/ie7L92dN43gChHeV4reiSrZAfLX31J7r52qYkX9Z0su4IknPYy92yvmtUK2rMbfKqOzx9jIpW MZ0B6LOQMEvNTqNVmBHAcG2siFDdoOWiNADUDqNYPmstqTtpNqVj9jll33gIzQuTGZh9IMgUxu8FL SrcuQjpYOOoDjN8F1mrY3qfn9p17AT3RVTBC9MedtD8rWQaavUG6BQQDbxxpwSf1AUj6tZRdP0Zoj 3ZYWAxjKw==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1koy16-0000Oe-TK; Tue, 15 Dec 2020 00:16:36 +0000 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1koy13-0000Nv-Pu for linux-arm-kernel@lists.infradead.org; Tue, 15 Dec 2020 00:16:34 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1607991393; 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=+KH49WHOC8U/vy7q7vIiLi7+DPF7822/r/b8oPP/btI=; b=eEFc6JrPa7iXH/eDmnj0bI3EVJ6ICdPc5JSoKVjk8q+vBEGtaGAHO8Q8ljRZN/55mWAR2I 1HkMzyB4sNSK7bEbtjH5mV9Fp7Cx7qGklyKlhOMJ1b2XPFsR0A4RjS/npMRWFGhJ9lnBp5 PA8HFZznpbDPWvNua9JWs7nuyTb/KpM= 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-291-aQP1cyCSMyiy2PSi3XYmag-1; Mon, 14 Dec 2020 19:16:29 -0500 X-MC-Unique: aQP1cyCSMyiy2PSi3XYmag-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id AC33E1922960; Tue, 15 Dec 2020 00:16:25 +0000 (UTC) Received: from omen.home (ovpn-112-193.phx2.redhat.com [10.3.112.193]) by smtp.corp.redhat.com (Postfix) with ESMTP id C55F510023B8; Tue, 15 Dec 2020 00:16:23 +0000 (UTC) Date: Mon, 14 Dec 2020 17:16:23 -0700 From: Alex Williamson To: zhukeqian Subject: Re: [PATCH 1/7] vfio: iommu_type1: Clear added dirty bit when unwind pin Message-ID: <20201214171623.6e909138@omen.home> In-Reply-To: References: <20201210073425.25960-1-zhukeqian1@huawei.com> <20201210073425.25960-2-zhukeqian1@huawei.com> <20201210121646.24fb3cd8@omen.home> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201214_191633_900304_8FFE2D4D X-CRM114-Status: GOOD ( 30.43 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: jiangkunkun@huawei.com, Andrew Morton , kvm@vger.kernel.org, Suzuki K Poulose , Marc Zyngier , Joerg Roedel , Cornelia Huck , linux-kernel@vger.kernel.org, Sean Christopherson , Alexios Zavras , iommu@lists.linux-foundation.org, Mark Brown , James Morse , Julien Thierry , Catalin Marinas , wanghaibin.wang@huawei.com, Thomas Gleixner , Will Deacon , kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org, Robin Murphy Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, 11 Dec 2020 14:51:47 +0800 zhukeqian wrote: > On 2020/12/11 3:16, Alex Williamson wrote: > > On Thu, 10 Dec 2020 15:34:19 +0800 > > Keqian Zhu wrote: > > > >> Currently we do not clear added dirty bit of bitmap when unwind > >> pin, so if pin failed at halfway, we set unnecessary dirty bit > >> in bitmap. Clearing added dirty bit when unwind pin, userspace > >> will see less dirty page, which can save much time to handle them. > >> > >> Note that we should distinguish the bits added by pin and the bits > >> already set before pin, so introduce bitmap_added to record this. > >> > >> Signed-off-by: Keqian Zhu > >> --- > >> drivers/vfio/vfio_iommu_type1.c | 33 ++++++++++++++++++++++----------- > >> 1 file changed, 22 insertions(+), 11 deletions(-) > >> > >> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c > >> index 67e827638995..f129d24a6ec3 100644 > >> --- a/drivers/vfio/vfio_iommu_type1.c > >> +++ b/drivers/vfio/vfio_iommu_type1.c > >> @@ -637,7 +637,11 @@ static int vfio_iommu_type1_pin_pages(void *iommu_data, > >> struct vfio_iommu *iommu = iommu_data; > >> struct vfio_group *group; > >> int i, j, ret; > >> + unsigned long pgshift = __ffs(iommu->pgsize_bitmap); > >> unsigned long remote_vaddr; > >> + unsigned long bitmap_offset; > >> + unsigned long *bitmap_added; > >> + dma_addr_t iova; > >> struct vfio_dma *dma; > >> bool do_accounting; > >> > >> @@ -650,6 +654,12 @@ static int vfio_iommu_type1_pin_pages(void *iommu_data, > >> > >> mutex_lock(&iommu->lock); > >> > >> + bitmap_added = bitmap_zalloc(npage, GFP_KERNEL); > >> + if (!bitmap_added) { > >> + ret = -ENOMEM; > >> + goto pin_done; > >> + } > > > > > > This is allocated regardless of whether dirty tracking is enabled, so > > this adds overhead to the common case in order to reduce user overhead > > (not correctness) in the rare condition that dirty tracking is enabled, > > and the even rarer condition that there's a fault during that case. > > This is not a good trade-off. Thanks, > > Hi Alex, > > We can allocate the bitmap when dirty tracking is active, do you accept this? > Or we can set the dirty bitmap after all pins succeed, but this costs cpu time > to locate vfio_dma with iova. TBH I don't see this as a terribly significant problem, in the rare event of an error with dirty tracking enabled, the user might see some pages marked dirty that were not successfully pinned by the mdev vendor driver. The solution shouldn't impose more overhead than the original issue. Thanks, Alex > >> + > >> /* Fail if notifier list is empty */ > >> if (!iommu->notifier.head) { > >> ret = -EINVAL; > >> @@ -664,7 +674,6 @@ static int vfio_iommu_type1_pin_pages(void *iommu_data, > >> do_accounting = !IS_IOMMU_CAP_DOMAIN_IN_CONTAINER(iommu); > >> > >> for (i = 0; i < npage; i++) { > >> - dma_addr_t iova; > >> struct vfio_pfn *vpfn; > >> > >> iova = user_pfn[i] << PAGE_SHIFT; > >> @@ -699,14 +708,10 @@ static int vfio_iommu_type1_pin_pages(void *iommu_data, > >> } > >> > >> if (iommu->dirty_page_tracking) { > >> - unsigned long pgshift = __ffs(iommu->pgsize_bitmap); > >> - > >> - /* > >> - * Bitmap populated with the smallest supported page > >> - * size > >> - */ > >> - bitmap_set(dma->bitmap, > >> - (iova - dma->iova) >> pgshift, 1); > >> + /* Populated with the smallest supported page size */ > >> + bitmap_offset = (iova - dma->iova) >> pgshift; > >> + if (!test_and_set_bit(bitmap_offset, dma->bitmap)) > >> + set_bit(i, bitmap_added); > >> } > >> } > >> ret = i; > >> @@ -722,14 +727,20 @@ static int vfio_iommu_type1_pin_pages(void *iommu_data, > >> pin_unwind: > >> phys_pfn[i] = 0; > >> for (j = 0; j < i; j++) { > >> - dma_addr_t iova; > >> - > >> iova = user_pfn[j] << PAGE_SHIFT; > >> dma = vfio_find_dma(iommu, iova, PAGE_SIZE); > >> vfio_unpin_page_external(dma, iova, do_accounting); > >> phys_pfn[j] = 0; > >> + > >> + if (test_bit(j, bitmap_added)) { > >> + bitmap_offset = (iova - dma->iova) >> pgshift; > >> + clear_bit(bitmap_offset, dma->bitmap); > >> + } > >> } > >> pin_done: > >> + if (bitmap_added) > >> + bitmap_free(bitmap_added); > >> + > >> mutex_unlock(&iommu->lock); > >> return ret; > >> } > > > > . > > > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel