No description
aec0e86172
We met the DMAR fault both on hpsa P420i and P421 SmartArray controllers under kdump, it can be steadily reproduced on several different machines, the dmesg log is like: HP HPSA Driver (v 3.4.16-0) hpsa 0000:02:00.0: using doorbell to reset controller hpsa 0000:02:00.0: board ready after hard reset. hpsa 0000:02:00.0: Waiting for controller to respond to no-op DMAR: Setting identity map for device 0000:02:00.0 [0xe8000 - 0xe8fff] DMAR: Setting identity map for device 0000:02:00.0 [0xf4000 - 0xf4fff] DMAR: Setting identity map for device 0000:02:00.0 [0xbdf6e000 - 0xbdf6efff] DMAR: Setting identity map for device 0000:02:00.0 [0xbdf6f000 - 0xbdf7efff] DMAR: Setting identity map for device 0000:02:00.0 [0xbdf7f000 - 0xbdf82fff] DMAR: Setting identity map for device 0000:02:00.0 [0xbdf83000 - 0xbdf84fff] DMAR: DRHD: handling fault status reg 2 DMAR: [DMA Read] Request device [02:00.0] fault addr fffff000 [fault reason 06] PTE Read access is not set hpsa 0000:02:00.0: controller message 03:00 timed out hpsa 0000:02:00.0: no-op failed; re-trying After some debugging, we found that the fault addr is from DMA initiated at the driver probe stage after reset(not in-flight DMA), and the corresponding pte entry value is correct, the fault is likely due to the old iommu caches of the in-flight DMA before it. Thus we need to flush the old cache after context mapping is setup for the device, where the device is supposed to finish reset at its driver probe stage and no in-flight DMA exists hereafter. I'm not sure if the hardware is responsible for invalidating all the related caches allocated in the iommu hardware before, but seems not the case for hpsa, actually many device drivers have problems in properly resetting the hardware. Anyway flushing (again) by software in kdump kernel when the device gets context mapped which is a quite infrequent operation does little harm. With this patch, the problematic machine can survive the kdump tests. CC: Myron Stowe <myron.stowe@gmail.com> CC: Joseph Szczypek <jszczype@redhat.com> CC: Don Brace <don.brace@microsemi.com> CC: Baoquan He <bhe@redhat.com> CC: Dave Young <dyoung@redhat.com> Fixes: |
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Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.