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Poison (or ECC) errors can be very common on a large size cluster. The kernel MM currently does not handle ECC errors / poison on a memory region that is not backed by struct pages. If a memory region mapped using remap_pfn_range() for example, but not added to the kernel, MM will not have associated struct pages. Add a new mechanism to handle memory failure on such memory. Make kernel MM expose a function to allow modules managing the device memory to register the device memory SPA and the address space associated it. MM maintains this information as an interval tree. On poison, MM can search for the range that the poisoned PFN belong and use the address_space to determine the mapping VMA. In this implementation, kernel MM follows the following sequence that is largely similar to the memory_failure() handler for struct page backed memory: 1. memory_failure() is triggered on reception of a poison error. An absence of struct page is detected and consequently memory_failure_pfn() is executed. 2. memory_failure_pfn() collects the processes mapped to the PFN. 3. memory_failure_pfn() sends SIGBUS to all the processes mapping the faulty PFN using kill_procs(). Note that there is one primary difference versus the handling of the poison on struct pages, which is to skip unmapping to the faulty PFN. This is done to handle the huge PFNMAP support added recently [1] that enables VM_PFNMAP vmas to map at PMD or PUD level. A poison to a PFN mapped in such as way would need breaking the PMD/PUD mapping into PTEs that will get mirrored into the S2. This can greatly increase the cost of table walks and have a major performance impact. Link: https://lore.kernel.org/all/20240826204353.2228736-1-peterx@redhat.com/ [1] Link: https://lkml.kernel.org/r/20251102184434.2406-3-ankita@nvidia.com Signed-off-by: Ankit Agrawal <ankita@nvidia.com> Cc: Aniket Agashe <aniketa@nvidia.com> Cc: Borislav Betkov <bp@alien8.de> Cc: David Hildenbrand <david@redhat.com> Cc: Hanjun Guo <guohanjun@huawei.com> Cc: Ira Weiny <ira.weiny@intel.com> Cc: Jason Gunthorpe <jgg@nvidia.com> Cc: Joanthan Cameron <Jonathan.Cameron@huawei.com> Cc: Kevin Tian <kevin.tian@intel.com> Cc: Kirti Wankhede <kwankhede@nvidia.com> Cc: Len Brown <lenb@kernel.org> Cc: Liam Howlett <liam.howlett@oracle.com> Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: "Luck, Tony" <tony.luck@intel.com> Cc: Matthew R. Ochs <mochs@nvidia.com> Cc: Mauro Carvalho Chehab <mchehab@kernel.org> Cc: Miaohe Lin <linmiaohe@huawei.com> Cc: Michal Hocko <mhocko@suse.com> Cc: Mike Rapoport <rppt@kernel.org> Cc: Naoya Horiguchi <nao.horiguchi@gmail.com> Cc: Neo Jia <cjia@nvidia.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Shuai Xue <xueshuai@linux.alibaba.com> Cc: Smita Koralahalli Channabasappa <smita.koralahallichannabasappa@amd.com> Cc: Suren Baghdasaryan <surenb@google.com> Cc: Tarun Gupta <targupta@nvidia.com> Cc: Uwe Kleine-König <u.kleine-koenig@baylibre.com> Cc: Vikram Sethi <vsethi@nvidia.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Zhi Wang <zhiw@nvidia.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.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 reStructuredText 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.