From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [192.55.52.88]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 068984432 for ; Mon, 11 Sep 2023 12:46:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1694436394; x=1725972394; h=message-id:date:mime-version:cc:subject:to:references: from:in-reply-to:content-transfer-encoding; bh=XG3f/Go4Kskr9FPWHx1DIAciSaD0sIA1smH1YceAZ4E=; b=PdsMkpo9uo7m5gg8bnAGiEPAfjzga2mPNA9ApGFf8JFubZI+gWDVpIH0 mvskMawx7nlpqasiN4ObxJe/vb4/wXVUDmMOPBv0AAVkXpFPw7psx2nPK QiklcTmERWpuxmkdFDPhNoSp9AcRW9lZ1fSvH/zHsnxCh2INFNA/QLa7F M/0mbukRsryPB+ev3tpuKYREBs1SVrkEemhu3UxwHNjdbcazc+1kPl5g6 ZCxCori9uLzazIvAnNn40+PXibLKz0qcNnOXRrdfhTvLBW6VH3tOW57M6 LJacEl0NeY5mFSpMtXziht52549ppsQMVhb3MkaIkUjlEdGNGcIlq1PsG Q==; X-IronPort-AV: E=McAfee;i="6600,9927,10830"; a="409038061" X-IronPort-AV: E=Sophos;i="6.02,244,1688454000"; d="scan'208";a="409038061" Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by fmsmga101.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 Sep 2023 05:46:32 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10830"; a="808815482" X-IronPort-AV: E=Sophos;i="6.02,244,1688454000"; d="scan'208";a="808815482" Received: from blu2-mobl.ccr.corp.intel.com (HELO [10.255.28.234]) ([10.255.28.234]) by fmsmga008-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 Sep 2023 05:46:28 -0700 Message-ID: Date: Mon, 11 Sep 2023 20:46:26 +0800 Precedence: bulk X-Mailing-List: iommu@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.15.0 Cc: baolu.lu@linux.intel.com, "Liu, Yi L" , Jacob Pan , "iommu@lists.linux.dev" , "kvm@vger.kernel.org" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH v4 09/10] iommu: Make iommu_queue_iopf() more generic Content-Language: en-US To: "Tian, Kevin" , Joerg Roedel , Will Deacon , Robin Murphy , Jason Gunthorpe , Jean-Philippe Brucker , Nicolin Chen References: <20230825023026.132919-1-baolu.lu@linux.intel.com> <20230825023026.132919-10-baolu.lu@linux.intel.com> From: Baolu Lu In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 2023/9/11 14:57, Tian, Kevin wrote: >> From: Baolu Lu >> Sent: Tuesday, September 5, 2023 1:24 PM >> >> Hi Kevin, >> >> I am trying to address this issue in below patch. Does it looks sane to >> you? >> >> iommu: Consolidate per-device fault data management >> >> The per-device fault data is a data structure that is used to store >> information about faults that occur on a device. This data is allocated >> when IOPF is enabled on the device and freed when IOPF is disabled. The >> data is used in the paths of iopf reporting, handling, responding, and >> draining. >> >> The fault data is protected by two locks: >> >> - dev->iommu->lock: This lock is used to protect the allocation and >> freeing of the fault data. >> - dev->iommu->fault_parameter->lock: This lock is used to protect the >> fault data itself. >> >> Improve the iopf code to enforce this lock mechanism and add a reference >> counter in the fault data to avoid use-after-free issue. >> > > Can you elaborate the use-after-free issue and why a new user count > is required? I was concerned that when iommufd uses iopf, page fault report/response may occur simultaneously with enable/disable PRI. Currently, this is not an issue as the enable/disable PRI is in its own path. In the future, we may discard this interface and enable PRI when attaching the first PRI-capable domain, and disable it when detaching the last PRI-capable domain. > > btw a Fix tag is required given this mislocking issue has been there for > quite some time... I don't see any real issue fixed by this change. It's only a lock refactoring after the code refactoring and preparing it for iommufd use. Perhaps I missed anything? Best regards, baolu