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[142.68.80.239]) by smtp.gmail.com with ESMTPSA id u10-20020a0cdd0a000000b0069b60baec46sm4402412qvk.146.2024.04.22.12.31.00 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 22 Apr 2024 12:31:00 -0700 (PDT) Received: from jgg by wakko with local (Exim 4.95) (envelope-from ) id 1ryzNT-0015IM-Mf; Mon, 22 Apr 2024 16:30:59 -0300 Date: Mon, 22 Apr 2024 16:30:59 -0300 From: Jason Gunthorpe To: Baolu Lu Cc: Tomasz Jeznach , Joerg Roedel , Will Deacon , Robin Murphy , Paul Walmsley , Palmer Dabbelt , Albert Ou , Anup Patel , Sunil V L , Nick Kossifidis , Sebastien Boeuf , Rob Herring , Krzysztof Kozlowski , Conor Dooley , devicetree@vger.kernel.org, iommu@lists.linux.dev, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, linux@rivosinc.com Subject: Re: [PATCH v2 7/7] iommu/riscv: Paging domain support Message-ID: <20240422193059.GC231144@ziepe.ca> References: <301244bc3ff5da484b46d3fecc931cdad7d2806f.1713456598.git.tjeznach@rivosinc.com> <2f2750cd-a5bf-4486-8f50-c93d246f8b0c@linux.intel.com> Precedence: bulk X-Mailing-List: iommu@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <2f2750cd-a5bf-4486-8f50-c93d246f8b0c@linux.intel.com> On Mon, Apr 22, 2024 at 01:21:05PM +0800, Baolu Lu wrote: > > + /* Track domain to devices mapping. */ > > + if (bond) > > + list_add_rcu(&bond->list, &domain->bonds); > > + > > + /* Remove tracking from previous domain, if needed. */ > > + iommu_domain = iommu_get_domain_for_dev(dev); > > Calling iommu_get_domain_for_dev() in the domain attaching path is very > fragile because it heavily depends on the order of calling the attach > callback and setting the domain pointer in the core. We have a couple places doing this already, the core code accomodates it well enough for deleting from a list.. So I think it is OK to keep doing. > Perhaps the driver can use dev_iommu_priv_set/get() to keep the active > domain in the per-device private data? > > > + if (iommu_domain && !!(iommu_domain->type & __IOMMU_DOMAIN_PAGING)) { > > + domain = iommu_domain_to_riscv(iommu_domain); > > + bond = NULL; > > + rcu_read_lock(); > > + list_for_each_entry_rcu(b, &domain->bonds, list) { > > + if (b->dev == dev) { > > + bond = b; > > + break; > > + } > > + } > > + rcu_read_unlock(); But now that I look again, this is not safe, you have to hold some kind of per-domain lock to mutate the list. rcu_*read*_lock() cannot be used for write. Jason 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 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 1A51CC4345F for ; Mon, 22 Apr 2024 19:31:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: 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=mTM0lkeRg+4rJ9Z074SRN3zrdSDNJ+SzfxQqRfa0s8Y=; b=Bt38/RZiRDo6bG kuYzQSovcFi5mS+cMMTlb7TJD48yMOiiyAWsMgl8pJqnWRp/30+sCxB5K4TMoaptefA0SZTG5W4tN 16KGXD3s5ThhZYGdcXU5NzL6EiNxnSTZGbl7Se83f+3KNiWnjxxMT2pevftmOvUju8WJdvyfjsKGh YlBoKkleu1c9IAgu0yJd85cwtLKsH3nSV2YMc2j7e9I7VNRcjOe1lHj6XQt/h1M0Yy19TLWartlws QXLXL2XMnjazsLrl2/KbYSAJnhUeTluGAH1r5/RBdqbfYlgg1dBJtke4VuZr3dmrTN7HFjK0xRoKb nRFBBLvzBO52Vzl/Lxng==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1ryzNd-0000000EoJH-16f7; Mon, 22 Apr 2024 19:31:09 +0000 Received: from mail-il1-x135.google.com ([2607:f8b0:4864:20::135]) by bombadil.infradead.org with esmtps (Exim 4.97.1 #2 (Red Hat Linux)) id 1ryzNY-0000000EoFH-270T for linux-riscv@lists.infradead.org; Mon, 22 Apr 2024 19:31:08 +0000 Received: by mail-il1-x135.google.com with SMTP id e9e14a558f8ab-36c11a66458so2902215ab.0 for ; Mon, 22 Apr 2024 12:31:02 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ziepe.ca; s=google; t=1713814261; x=1714419061; darn=lists.infradead.org; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=yh3rgiRcQXBNCIidxjhakiopwH4ays77o8Kd/hCbWDI=; b=dDRHmgZiQT5Gn0vuYty2Ef74zIR1NvIkPmUL5//UMiRkryuxWdw1uJH1ZUhevgcOud rzadLUjZOKwH+ZJqTCVl/i5u4n4OTSDigf3l+gQyEHmlH0N/xm4mfW2MAQXi/f+CvsDZ MP2xMv+7wj9S/OZjRYsHmir95L/wodXsKmbSm1S7uu0ZT/R9kS0mzCuQAF5rMYSo2ARi U93WRmf0rnD2RWl5kdSD0TNnbhB/A5ey3VSpqPp3qHjL0GQsEDSwQ25KetjObKp1sJil 4CEJjfjKGzkbaxRT/w8XhqYfQIedQuLXCCIUi5qFgrxXfdkOVUBNlqUqBpZEj4AmYN+v IPPg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1713814261; x=1714419061; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=yh3rgiRcQXBNCIidxjhakiopwH4ays77o8Kd/hCbWDI=; b=arjGybFsd0ZkJXAAO4w8u8N5kWJDkoah+T5IV9hG31+JY5aGAtWmPEIumX7s0HExKf 14wLdbRLrZbN14ndhXjSCydCCQ247NLUA7ebR5/HVz9rYCO3Mox0PAFla+QQZzgGN+b9 gLRqBsFqGtZN4cxdLvV2NVv5v6FFgFjX945TGfHnMjrUadwoy0QYvZQSHnxBJvztspyx egoAKam2qfekqy7PBEgr3hG2462TcOuq9EzdrIEEI3M/cwOFmwYcTWHbiij22rmgHK6S MRrlKof+yBU1v1C2eQ5ufIwtVlzDWY2mYeoz3Kiuyrmaoz6SyM/GdxOeUpJSO+HotqEe Y2Ow== X-Forwarded-Encrypted: i=1; AJvYcCX8Xp/BhaxGL/vUq083ap9diO0wzTLqYRWIHCs1O+az9aidyrY5M92kO0Cinr+UfIivZ1Qpz8ydJqtF5qxms8Zoj5Ohkyi0ZaUQlfn8NyIb X-Gm-Message-State: AOJu0Yz4CjlR7SD0sLB847SEtlqVD7jvEzX+G29y2j60kdOsYYRs2JC+ 3UaHPXfR5BRn+X3LTkS1nzO5nmuw+OdPXPU8UGDuWSPGoU2zMyLdaOqJ0zERK60= X-Google-Smtp-Source: AGHT+IH895F9KLddG1s2eZCz4/bKHter3T6UNI8IsPcUq25R04uAGE5maPekZYiqnwm1PrKXKmatlA== X-Received: by 2002:a05:6e02:b45:b0:36b:1868:fab7 with SMTP id f5-20020a056e020b4500b0036b1868fab7mr15663679ilu.15.1713814261611; Mon, 22 Apr 2024 12:31:01 -0700 (PDT) Received: from ziepe.ca (hlfxns017vw-142-68-80-239.dhcp-dynamic.fibreop.ns.bellaliant.net. [142.68.80.239]) by smtp.gmail.com with ESMTPSA id u10-20020a0cdd0a000000b0069b60baec46sm4402412qvk.146.2024.04.22.12.31.00 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 22 Apr 2024 12:31:00 -0700 (PDT) Received: from jgg by wakko with local (Exim 4.95) (envelope-from ) id 1ryzNT-0015IM-Mf; Mon, 22 Apr 2024 16:30:59 -0300 Date: Mon, 22 Apr 2024 16:30:59 -0300 From: Jason Gunthorpe To: Baolu Lu Subject: Re: [PATCH v2 7/7] iommu/riscv: Paging domain support Message-ID: <20240422193059.GC231144@ziepe.ca> References: <301244bc3ff5da484b46d3fecc931cdad7d2806f.1713456598.git.tjeznach@rivosinc.com> <2f2750cd-a5bf-4486-8f50-c93d246f8b0c@linux.intel.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <2f2750cd-a5bf-4486-8f50-c93d246f8b0c@linux.intel.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240422_123104_742147_3535EDB4 X-CRM114-Status: GOOD ( 15.42 ) X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Anup Patel , devicetree@vger.kernel.org, Conor Dooley , Albert Ou , Tomasz Jeznach , linux@rivosinc.com, Robin Murphy , Joerg Roedel , linux-kernel@vger.kernel.org, Rob Herring , Sebastien Boeuf , iommu@lists.linux.dev, Palmer Dabbelt , Paul Walmsley , Nick Kossifidis , Krzysztof Kozlowski , Will Deacon , linux-riscv@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org On Mon, Apr 22, 2024 at 01:21:05PM +0800, Baolu Lu wrote: > > + /* Track domain to devices mapping. */ > > + if (bond) > > + list_add_rcu(&bond->list, &domain->bonds); > > + > > + /* Remove tracking from previous domain, if needed. */ > > + iommu_domain = iommu_get_domain_for_dev(dev); > > Calling iommu_get_domain_for_dev() in the domain attaching path is very > fragile because it heavily depends on the order of calling the attach > callback and setting the domain pointer in the core. We have a couple places doing this already, the core code accomodates it well enough for deleting from a list.. So I think it is OK to keep doing. > Perhaps the driver can use dev_iommu_priv_set/get() to keep the active > domain in the per-device private data? > > > + if (iommu_domain && !!(iommu_domain->type & __IOMMU_DOMAIN_PAGING)) { > > + domain = iommu_domain_to_riscv(iommu_domain); > > + bond = NULL; > > + rcu_read_lock(); > > + list_for_each_entry_rcu(b, &domain->bonds, list) { > > + if (b->dev == dev) { > > + bond = b; > > + break; > > + } > > + } > > + rcu_read_unlock(); But now that I look again, this is not safe, you have to hold some kind of per-domain lock to mutate the list. rcu_*read*_lock() cannot be used for write. Jason _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv