From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.15]) (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 96430BE48; Fri, 23 Feb 2024 02:29:38 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=192.198.163.15 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708655380; cv=none; b=gPHsiw6l07Xju8oqG61stK7XCjrWc/Ifmaq7gOCxivGgxSsRu9yuuw71vpJkE+ix1dG157sgrlp6lIlShD93vMqaMWIRFyeAImbDq3ollOY/QOZaVTVwv8i/VjHI92+lt/HCM9R/Qlh+BhrfHSiWLpvmCCMSvqpwzgfQaNH1rGM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708655380; c=relaxed/simple; bh=PonAp4P0aFtIcd+rOQ5XyV76Ss3r/bbPSNZvKReTEb4=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=eNnDsvn11UgBwbp9jOl5ssNGD1q4Cm1PXiRXS9VyaYSAtaUMEOUt/Fn2NJxeQE9Fex6QyUobHVEgvND6Hg6HTkrNKigfiFkP/v6fdXuN5kUsO91m2SJ7oR2AeUE9fMd3gIHQpUblhitCprrYyngOvqf8zq9Py45K6H8qiHe3QZg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com; spf=none smtp.mailfrom=linux.intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=UA//yCiM; arc=none smtp.client-ip=192.198.163.15 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="UA//yCiM" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1708655379; x=1740191379; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=PonAp4P0aFtIcd+rOQ5XyV76Ss3r/bbPSNZvKReTEb4=; b=UA//yCiMBciyyFDeOhKkTyVk8cWAcRzTOmrnU9AvdkZMqqEf6+L6oa+t ssOJ6JPW+6txmZ/xRAM+1LXi8ZTuseDTz4QMq8XHMUJ9C2A5qeBoOLAUK FDBZM33/BdfxGjL0dBT/zKybXb8Abbe/U7G1Q8eX2I0VmqfybFEosHPI/ 1edqiVWLZhVjmWK+tKDxW8gOPUDkxu/UmWpTTnn901OwIwrE89rA9/1rY Vtfx3a8mxz/N7UgQswUEdvye7CdJ6LFR1EQnlPS7ccHs3o0jFLRoaREN9 ikE+1/svfbTgJb9ZczLjYjnKL2JBLMYmRoc27vcNASl0Su0gjPx2LDf98 g==; X-IronPort-AV: E=McAfee;i="6600,9927,10992"; a="3110258" X-IronPort-AV: E=Sophos;i="6.06,179,1705392000"; d="scan'208";a="3110258" Received: from orviesa006.jf.intel.com ([10.64.159.146]) by fmvoesa109.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 22 Feb 2024 18:29:38 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.06,179,1705392000"; d="scan'208";a="6171175" Received: from zhaohaif-mobl.ccr.corp.intel.com (HELO [10.255.30.59]) ([10.255.30.59]) by orviesa006-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 22 Feb 2024 18:29:32 -0800 Message-ID: <2d1788da-521c-4531-a159-81d2fb801d6c@linux.intel.com> Date: Fri, 23 Feb 2024 10:29:28 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v13 3/3] iommu/vt-d: improve ITE fault handling if target device isn't valid To: Dan Carpenter Cc: baolu.lu@linux.intel.com, bhelgaas@google.com, robin.murphy@arm.com, jgg@ziepe.ca, kevin.tian@intel.com, dwmw2@infradead.org, will@kernel.org, lukas@wunner.de, yi.l.liu@intel.com, iommu@lists.linux.dev, linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org References: <20240222090251.2849702-1-haifeng.zhao@linux.intel.com> <20240222090251.2849702-4-haifeng.zhao@linux.intel.com> From: Ethan Zhao In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 2/22/2024 7:24 PM, Dan Carpenter wrote: > I'm sorry, I'm coming into this late and this is the first time I have > reviewed this patch. I see that we are at v13, and I hate to come in > with picky comments when a patch has already gone through 13 > revisions... Never mind that. some are totally new. > On Thu, Feb 22, 2024 at 04:02:51AM -0500, Ethan Zhao wrote: >> Because surprise removal could happen anytime, e.g. user could request safe >> removal to EP(endpoint device) via sysfs and brings its link down to do >> surprise removal cocurrently. such aggressive cases would cause ATS >> invalidation request issued to non-existence target device, then deadly >> loop to retry that request after ITE fault triggered in interrupt context. >> this patch aims to optimize the ITE handling by checking the target device >> presence state to avoid retrying the timeout request blindly, thus avoid >> hard lockup or system hang. >> >> Devices are valid ATS invalidation request target only when they reside > "valid invalidation" is awkward wording. Can we instead say: If you read them together, sounds like tongue twister. but here "ATS invalidation request target" is one term in PCIe spec. > > Devices should only be invalidated when they are in the > iommu->device_rbtree (probed, not released) and present. > >> in the iommu->device_rbtre (probed, not released) and present. > ^ > Missing e in _rbtree. Yup. >> Signed-off-by: Ethan Zhao > This patch should have a Fixes tags and be backported to stable kernels. > I think it goes back all the way... > > Fixes: 704126ad81b8 ("VT-d: handle Invalidation Queue Error to avoid system hang") Sounds reasonable. > >> --- >> drivers/iommu/intel/dmar.c | 25 +++++++++++++++++++++++++ >> 1 file changed, 25 insertions(+) >> >> diff --git a/drivers/iommu/intel/dmar.c b/drivers/iommu/intel/dmar.c >> index d14797aabb7a..d01d68205557 100644 >> --- a/drivers/iommu/intel/dmar.c >> +++ b/drivers/iommu/intel/dmar.c >> @@ -1273,6 +1273,9 @@ static int qi_check_fault(struct intel_iommu *iommu, int index, int wait_index) >> { >> u32 fault; >> int head, tail; >> + u64 iqe_err, ite_sid; >> + struct device *dev = NULL; >> + struct pci_dev *pdev = NULL; >> struct q_inval *qi = iommu->qi; >> int shift = qi_shift(iommu); >> >> @@ -1317,6 +1320,13 @@ static int qi_check_fault(struct intel_iommu *iommu, int index, int wait_index) >> tail = readl(iommu->reg + DMAR_IQT_REG); >> tail = ((tail >> shift) - 1 + QI_LENGTH) % QI_LENGTH; >> >> + /* >> + * SID field is valid only when the ITE field is Set in FSTS_REG >> + * see Intel VT-d spec r4.1, section 11.4.9.9 >> + */ >> + iqe_err = dmar_readq(iommu->reg + DMAR_IQER_REG); >> + ite_sid = DMAR_IQER_REG_ITESID(iqe_err); >> + >> writel(DMA_FSTS_ITE, iommu->reg + DMAR_FSTS_REG); >> pr_info("Invalidation Time-out Error (ITE) cleared\n"); >> >> @@ -1326,6 +1336,21 @@ static int qi_check_fault(struct intel_iommu *iommu, int index, int wait_index) >> head = (head - 2 + QI_LENGTH) % QI_LENGTH; >> } while (head != tail); >> >> + /* >> + * If got ITE, we need to check if the sid of ITE is one of the >> + * current valid ATS invalidation target devices, if no, or the >> + * target device isn't presnet, don't try this request anymore. >> + * 0 value of ite_sid means old VT-d device, no ite_sid value. >> + */ > This comment is kind of confusing. Really confusing ? this is typo there, resnet-> "present" > > /* > * If we have an ITE, then we need to check whether the sid of the ITE > * is in the rbtree (meaning it is probed and not released), and that > * the PCI device is present. > */ > > My comment is slightly shorter but I think it has the necessary > information. > >> + if (ite_sid) { >> + dev = device_rbtree_find(iommu, ite_sid); >> + if (!dev || !dev_is_pci(dev)) >> + return -ETIMEDOUT; > -ETIMEDOUT is weird. The callers don't care which error code we return. > Change this to -ENODEV or something -ETIMEDOUT means prior ATS invalidation request hit timeout fault, and the caller really cares about the returned value. > >> + pdev = to_pci_dev(dev); >> + if (!pci_device_is_present(pdev) && >> + ite_sid == pci_dev_id(pci_physfn(pdev))) > The && confused me, but then I realized that probably "ite_sid == > pci_dev_id(pci_physfn(pdev))" is always true. Can we delete that part? Here is the fault handling, just double confirm nothing else goes wrong -- beyond the assumption. > > pdev = to_pci_dev(dev); > if (!pci_device_is_present(pdev)) > return -ENODEV; > > >> + return -ETIMEDOUT; > -ENODEV. The ATS invalidation request could be sent from userland in later code, the userland code will care about the returned value, -ENODEV is one aspect of the fact (target device not present), while -ETIMEDOUT is another (timeout happened). we couldn't return them both. > >> + } >> if (qi->desc_status[wait_index] == QI_ABORT) >> return -EAGAIN; >> } > Sorry, again for nit picking a v13 patch. I'm not a domain expert but > this patchset seems reasonable to me. Though this is the v13, it is based on new rbtree code, you are welcome. Thanks, Ethan > regards, > dan carpenter