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=-13.5 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,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 06D0EC2BB48 for ; Tue, 15 Dec 2020 00:16:39 +0000 (UTC) Received: from whitealder.osuosl.org (smtp1.osuosl.org [140.211.166.138]) (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 9973522209 for ; Tue, 15 Dec 2020 00:16:38 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9973522209 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=iommu-bounces@lists.linux-foundation.org Received: from localhost (localhost [127.0.0.1]) by whitealder.osuosl.org (Postfix) with ESMTP id 4DE2D87304; Tue, 15 Dec 2020 00:16:38 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from whitealder.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id E2K2ReF79PNq; Tue, 15 Dec 2020 00:16:36 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [140.211.9.56]) by whitealder.osuosl.org (Postfix) with ESMTP id B9F5287168; Tue, 15 Dec 2020 00:16:36 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id AB18EC0893; Tue, 15 Dec 2020 00:16:36 +0000 (UTC) Received: from silver.osuosl.org (smtp3.osuosl.org [140.211.166.136]) by lists.linuxfoundation.org (Postfix) with ESMTP id C86FDC013B for ; Tue, 15 Dec 2020 00:16:35 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by silver.osuosl.org (Postfix) with ESMTP id B20CF20511 for ; Tue, 15 Dec 2020 00:16:35 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from silver.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id C9yVkFttkkrb for ; Tue, 15 Dec 2020 00:16:34 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.7.6 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [216.205.24.124]) by silver.osuosl.org (Postfix) with ESMTPS id 2A5C02011A for ; Tue, 15 Dec 2020 00:16:34 +0000 (UTC) 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 Cc: jiangkunkun@huawei.com, Andrew Morton , kvm@vger.kernel.org, Suzuki K Poulose , Marc Zyngier , 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 X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" 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; > >> } > > > > . > > > _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu