Return-path: Received: from mail2.candelatech.com ([208.74.158.173]:60552 "EHLO mail2.candelatech.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751993AbdDNQTj (ORCPT ); Fri, 14 Apr 2017 12:19:39 -0400 Subject: Re: How to debug DMAR errors? To: Alexander Duyck References: Cc: "linux-wireless@vger.kernel.org" , netdev From: Ben Greear Message-ID: (sfid-20170414_181951_032359_5B6C9587) Date: Fri, 14 Apr 2017 09:19:36 -0700 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Sender: linux-wireless-owner@vger.kernel.org List-ID: On 04/14/2017 08:45 AM, Alexander Duyck wrote: > On Thu, Apr 13, 2017 at 11:12 AM, Ben Greear wrote: >> Hello, >> >> I have been seeing a regular occurrence of DMAR errors, looking something >> like this when testing my ath10k driver/firmware under some specific loads >> (maximum receive of 512 byte frames in AP mode): >> >> DMAR: DRHD: handling fault status reg 3 >> DMAR: [DMA Read] Request device [05:00.0] fault addr fd99f000 [fault reason >> 06] PTE Read access is not set >> ath10k_pci 0000:05:00.0: firmware crashed! (uuid >> 594b1393-ae35-42b5-9dec-74ff0c6791ff) >> >> So, I am wondering if there is any way I can get more information about what >> this fd99f000 address >> is? >> >> Once this problem hits, the entire OS locks hard (not even sysrq-boot will >> do anything), >> so I guess I would need the DMAR logic to print out more info on that >> address somehow. >> >> Thanks, >> Ben > > There isn't much more info to give you. The problem is that the device > at 5:00.0 attempted to read at fd99f000 even though it didn't have > permissions. In response this should trigger a PCI Master Abort > message to that function. It looks like the firmware for the device > doesn't handle that and so that is likely why things got hung. > > Really you would need to interrogate the ath10k_pci to see if there > is/was a mapping somewhere for that address and what it was supposed > to be used for. I'm working on a hook in DMAR logic to call into ath10k_pci when the error is seen, so the ath10k can dump debug info, including recent DMA addresses. My code is an awful hack so far, but if someone could add a clean way to register DMAR error callbacks, I think that would be very welcome. It might could tie into automated dma map/unmap debugging logic, and at the least, someone could write custom debugging callbacks for the driver(s) in question. Thanks, Ben > > - Alex > -- Ben Greear Candela Technologies Inc http://www.candelatech.com