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=-8.1 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 17C18C4332B for ; Tue, 24 Mar 2020 19:36:03 +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 D238520714 for ; Tue, 24 Mar 2020 19:36:02 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=nvidia.com header.i=@nvidia.com header.b="gbO5Pwjk" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D238520714 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=nvidia.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:54060 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jGpLG-0005io-2M for qemu-devel@archiver.kernel.org; Tue, 24 Mar 2020 15:36:02 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:49031) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jGpKL-0004nt-Ur for qemu-devel@nongnu.org; Tue, 24 Mar 2020 15:35:06 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1jGpKK-0007Le-SZ for qemu-devel@nongnu.org; Tue, 24 Mar 2020 15:35:05 -0400 Received: from hqnvemgate24.nvidia.com ([216.228.121.143]:11784) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1jGpKK-0007KO-MS for qemu-devel@nongnu.org; Tue, 24 Mar 2020 15:35:04 -0400 Received: from hqpgpgate101.nvidia.com (Not Verified[216.228.121.13]) by hqnvemgate24.nvidia.com (using TLS: TLSv1.2, DES-CBC3-SHA) id ; Tue, 24 Mar 2020 12:33:32 -0700 Received: from hqmail.nvidia.com ([172.20.161.6]) by hqpgpgate101.nvidia.com (PGP Universal service); Tue, 24 Mar 2020 12:35:03 -0700 X-PGP-Universal: processed; by hqpgpgate101.nvidia.com on Tue, 24 Mar 2020 12:35:03 -0700 Received: from [10.40.103.72] (172.20.13.39) by HQMAIL107.nvidia.com (172.20.187.13) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Tue, 24 Mar 2020 19:34:54 +0000 Subject: Re: [PATCH v15 Kernel 2/7] vfio iommu: Remove atomicity of ref_count of pinned pages To: Auger Eric , , References: <1584649004-8285-1-git-send-email-kwankhede@nvidia.com> <1584649004-8285-3-git-send-email-kwankhede@nvidia.com> X-Nvconfidentiality: public From: Kirti Wankhede Message-ID: Date: Wed, 25 Mar 2020 01:04:50 +0530 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: X-Originating-IP: [172.20.13.39] X-ClientProxiedBy: HQMAIL107.nvidia.com (172.20.187.13) To HQMAIL107.nvidia.com (172.20.187.13) Content-Type: text/plain; charset="windows-1252"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nvidia.com; s=n1; t=1585078412; bh=40wVc0Yor8YTosJnEQ2TGgBM6wIvNiRWDsFVZ7Q/Fjg=; h=X-PGP-Universal:Subject:To:CC:References:X-Nvconfidentiality:From: Message-ID:Date:User-Agent:MIME-Version:In-Reply-To: X-Originating-IP:X-ClientProxiedBy:Content-Type:Content-Language: Content-Transfer-Encoding; b=gbO5PwjkX/gKB+EUSCsbtRqYcPexTnIjStcBsnRgvqlKBBhAReRViuGL9KGrip2k0 alwsjRbBM3RM08beJomQv/L1sQqapeflSlKBP2U+VkH9scY8iV7pdV6urcQ4Go+bww MW62nZnfwjKBCykW750YUNfwjjAl3bVvAQvxYERWtHJhJzidFA2u49f4x/DRHET9sx Cb6MFYQRuZA+XurNLS8nB5k5kbhTNXqsADBAQ4nHW8jRIm24QmAKjYKmD7VUJsYDtb vdd5yOFWZSRBADJA/J85Z9VxOpuJ/6GHI4uaOEzp6BBGykCT7ekkE0uXNqYw3AsezB WmNRW9IEqjy8w== X-detected-operating-system: by eggs.gnu.org: Windows 7 or 8 [fuzzy] X-Received-From: 216.228.121.143 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: Zhengxiao.zx@Alibaba-inc.com, kevin.tian@intel.com, yi.l.liu@intel.com, yan.y.zhao@intel.com, kvm@vger.kernel.org, eskultet@redhat.com, ziye.yang@intel.com, qemu-devel@nongnu.org, cohuck@redhat.com, shuangtai.tst@alibaba-inc.com, dgilbert@redhat.com, zhi.a.wang@intel.com, mlevitsk@redhat.com, pasic@linux.ibm.com, aik@ozlabs.ru, eauger@redhat.com, felipe@nutanix.com, jonathan.davies@nutanix.com, changpeng.liu@intel.com, Ken.Xue@amd.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 3/24/2020 2:00 AM, Auger Eric wrote: > Hi Kirti, > > On 3/19/20 9:16 PM, Kirti Wankhede wrote: >> vfio_pfn.ref_count is always updated by holding iommu->lock, using atomic >> variable is overkill. >> >> Signed-off-by: Kirti Wankhede >> Reviewed-by: Neo Jia > Reviewed-by: Eric Auger > Thanks. Kirti. > Thanks > > Eric >> --- >> drivers/vfio/vfio_iommu_type1.c | 9 +++++---- >> 1 file changed, 5 insertions(+), 4 deletions(-) >> >> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c >> index 9fdfae1cb17a..70aeab921d0f 100644 >> --- a/drivers/vfio/vfio_iommu_type1.c >> +++ b/drivers/vfio/vfio_iommu_type1.c >> @@ -112,7 +112,7 @@ struct vfio_pfn { >> struct rb_node node; >> dma_addr_t iova; /* Device address */ >> unsigned long pfn; /* Host pfn */ >> - atomic_t ref_count; >> + unsigned int ref_count; >> }; >> >> struct vfio_regions { >> @@ -233,7 +233,7 @@ static int vfio_add_to_pfn_list(struct vfio_dma *dma, dma_addr_t iova, >> >> vpfn->iova = iova; >> vpfn->pfn = pfn; >> - atomic_set(&vpfn->ref_count, 1); >> + vpfn->ref_count = 1; >> vfio_link_pfn(dma, vpfn); >> return 0; >> } >> @@ -251,7 +251,7 @@ static struct vfio_pfn *vfio_iova_get_vfio_pfn(struct vfio_dma *dma, >> struct vfio_pfn *vpfn = vfio_find_vpfn(dma, iova); >> >> if (vpfn) >> - atomic_inc(&vpfn->ref_count); >> + vpfn->ref_count++; >> return vpfn; >> } >> >> @@ -259,7 +259,8 @@ static int vfio_iova_put_vfio_pfn(struct vfio_dma *dma, struct vfio_pfn *vpfn) >> { >> int ret = 0; >> >> - if (atomic_dec_and_test(&vpfn->ref_count)) { >> + vpfn->ref_count--; >> + if (!vpfn->ref_count) { >> ret = put_pfn(vpfn->pfn, dma->prot); >> vfio_remove_from_pfn_list(dma, vpfn); >> } >> >