From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [192.55.52.151]) (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 1DDB979C6; Thu, 28 Dec 2023 13:10:13 +0000 (UTC) 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="ecqsIWj3" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1703769014; x=1735305014; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=+h48D15/TNyIh+MOL0pe6S5/Owyp+lm7qG0IVc8QWuw=; b=ecqsIWj3/SlvYxiJdvQQ+jMFkjwvrob97Z5f24GKDHLN0Y2E1TNbOXSI tbB65H+6Rkjit3obz2CpR0EnuzqlrDGNFcphJcfCPmdDgp3nYoR6kTjFX uWmFBp4KvhdXtWl+cKBXgau33ZmA3OLzJ6TcBjaF8qhqKoUFjx2sRdQzf kQ9a6lT1Wa8OoNNP5wb176u2L5S8/g63yMr7TgGQDC7AO1DKNXsJj5MVz e/t/iGFWmqYpaEShk3h7HxXRrMA72H2SwrGEnNA4TGCV3a6v6lEG1dFR2 1UIchmJ2zJ8hATbMFiSJfTl28CdvHk6/PiYNcB5tnPHLmtpvCUeW3CN3T w==; X-IronPort-AV: E=McAfee;i="6600,9927,10936"; a="376701617" X-IronPort-AV: E=Sophos;i="6.04,312,1695711600"; d="scan'208";a="376701617" Received: from fmsmga004.fm.intel.com ([10.253.24.48]) by fmsmga107.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 28 Dec 2023 05:10:13 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10936"; a="848946415" X-IronPort-AV: E=Sophos;i="6.04,312,1695711600"; d="scan'208";a="848946415" Received: from zhaohaif-mobl.ccr.corp.intel.com (HELO [10.249.169.62]) ([10.249.169.62]) by fmsmga004-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 28 Dec 2023 05:10:10 -0800 Message-ID: Date: Thu, 28 Dec 2023 21:10:08 +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: [RFC PATCH v9 5/5] iommu/vt-d: don't loop for timeout ATS Invalidation request forever To: "Tian, Kevin" , "bhelgaas@google.com" , "baolu.lu@linux.intel.com" , "dwmw2@infradead.org" , "will@kernel.org" , "robin.murphy@arm.com" , "lukas@wunner.de" Cc: "linux-pci@vger.kernel.org" , "iommu@lists.linux.dev" , "linux-kernel@vger.kernel.org" References: <20231228001646.587653-1-haifeng.zhao@linux.intel.com> <20231228001646.587653-6-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 12/28/2023 4:38 PM, Tian, Kevin wrote: >> From: Ethan Zhao >> Sent: Thursday, December 28, 2023 8:17 AM >> >> When the ATS Invalidation request timeout happens, the qi_submit_sync() >> will restart and loop for the invalidation request forever till it is >> done, it will block another Invalidation thread such as the fq_timer >> to issue invalidation request, cause the system lockup as following >> >> [exception RIP: native_queued_spin_lock_slowpath+92] >> >> RIP: ffffffffa9d1025c RSP: ffffb202f268cdc8 RFLAGS: 00000002 >> >> RAX: 0000000000000101 RBX: ffffffffab36c2a0 RCX: 0000000000000000 >> >> RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffffab36c2a0 >> >> RBP: ffffffffab36c2a0 R8: 0000000000000001 R9: 0000000000000000 >> >> R10: 0000000000000010 R11: 0000000000000018 R12: 0000000000000000 >> >> R13: 0000000000000004 R14: ffff9e10d71b1c88 R15: ffff9e10d71b1980 >> >> ORIG_RAX: ffffffffffffffff CS: 0010 SS: 0018 >> >> #12 [ffffb202f268cdc8] native_queued_spin_lock_slowpath at >> ffffffffa9d1025c >> >> #13 [ffffb202f268cdc8] do_raw_spin_lock at ffffffffa9d121f1 >> >> #14 [ffffb202f268cdd8] _raw_spin_lock_irqsave at ffffffffaa51795b >> >> #15 [ffffb202f268cdf8] iommu_flush_dev_iotlb at ffffffffaa20df48 >> >> #16 [ffffb202f268ce28] iommu_flush_iova at ffffffffaa20e182 >> >> #17 [ffffb202f268ce60] iova_domain_flush at ffffffffaa220e27 >> >> #18 [ffffb202f268ce70] fq_flush_timeout at ffffffffaa221c9d >> >> #19 [ffffb202f268cea8] call_timer_fn at ffffffffa9d46661 >> >> #20 [ffffb202f268cf08] run_timer_softirq at ffffffffa9d47933 >> >> #21 [ffffb202f268cf98] __softirqentry_text_start at ffffffffaa8000e0 >> >> #22 [ffffb202f268cff0] asm_call_sysvec_on_stack at ffffffffaa60114f >> --- --- >> (the left part of exception see the hotplug case of ATS capable device) >> >> If one endpoint device just no response to the ATS Invalidation request, >> but is not gone, it will bring down the whole system, to avoid such >> case, don't try the timeout ATS Invalidation request forever. >> >> Signed-off-by: Ethan Zhao >> --- >> drivers/iommu/intel/dmar.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/drivers/iommu/intel/dmar.c b/drivers/iommu/intel/dmar.c >> index 76903a8bf963..206ab0b7294f 100644 >> --- a/drivers/iommu/intel/dmar.c >> +++ b/drivers/iommu/intel/dmar.c >> @@ -1457,7 +1457,7 @@ int qi_submit_sync(struct intel_iommu *iommu, >> struct qi_desc *desc, >> reclaim_free_desc(qi); >> raw_spin_unlock_irqrestore(&qi->q_lock, flags); >> >> - if (rc == -EAGAIN) >> + if (rc == -EAGAIN && type !=QI_DIOTLB_TYPE && type != >> QI_DEIOTLB_TYPE) >> goto restart; >> > this change is moot. > > -EAGAIN is set only when hardware detects a ATS invalidation completion > timeout in qi_check_fault(). so above just essentially kills the restart logic. This change is intended to break the restar login when device-TLB invalidation timeout happens, we don't know how long the ITE took if the device is just no reponse. > > I'd wait for the maintainer of this driver to comment. this part doesn't > look good but there might be some history reason so carefulness must > be paid. I would like to know the reason a hole is left here to hang the driver forever. Thanks, Ethan