a8a86631f4
commit 5ce97f4ec5e0f8726a5dda1710727b1ee9badcac upstream. The AMD IOMMU logs I/O page faults and such to a ring buffer in system memory, and this ring buffer can overflow. The AMD IOMMU spec has the following to say about the interrupt status bit that signals this overflow condition: EventOverflow: Event log overflow. RW1C. Reset 0b. 1 = IOMMU event log overflow has occurred. This bit is set when a new event is to be written to the event log and there is no usable entry in the event log, causing the new event information to be discarded. An interrupt is generated when EventOverflow = 1b and MMIO Offset 0018h[EventIntEn] = 1b. No new event log entries are written while this bit is set. Software Note: To resume logging, clear EventOverflow (W1C), and write a 1 to MMIO Offset 0018h[EventLogEn]. The AMD IOMMU driver doesn't currently implement this recovery sequence, meaning that if a ring buffer overflow occurs, logging of EVT/PPR/GA events will cease entirely. This patch implements the spec-mandated reset sequence, with the minor tweak that the hardware seems to want to have a 0 written to MMIO Offset 0018h[EventLogEn] first, before writing an 1 into this field, or the IOMMU won't actually resume logging events. Signed-off-by: Lennert Buytenhek <buytenh@arista.com> Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/YVrSXEdW2rzEfOvk@wantstofly.org Signed-off-by: Joerg Roedel <jroedel@suse.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
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.