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The page faults may be spurious because of the racy access to the page table. For example, a non-populated virtual page is accessed on 2 CPUs simultaneously, thus the page faults are triggered on both CPUs. However, it's possible that one CPU (say CPU A) cannot find the reason for the page fault if the other CPU (say CPU B) has changed the page table before the PTE is checked on CPU A. Most of the time, the spurious page faults can be ignored safely. However, if the page fault is for the write access, it's possible that a stale read-only TLB entry exists in the local CPU and needs to be flushed on some architectures. This is called the spurious page fault fixing. In the current kernel, there is spurious fault fixing support for pte, but not for huge pmd because no architectures need it. But in the next patch in the series, we will change the write protection fault handling logic on arm64, so that some stale huge pmd entries may remain in the TLB. These entries need to be flushed via the huge pmd spurious fault fixing mechanism. Signed-off-by: Huang Ying <ying.huang@linux.alibaba.com> Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Acked-by: David Hildenbrand <david@redhat.com> Acked-by: Zi Yan <ziy@nvidia.com> Cc: Will Deacon <will@kernel.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Baolin Wang <baolin.wang@linux.alibaba.com> Cc: Ryan Roberts <ryan.roberts@arm.com> Cc: Yang Shi <yang@os.amperecomputing.com> Cc: Christoph Lameter (Ampere) <cl@gentwo.org> Cc: Dev Jain <dev.jain@arm.com> Cc: Barry Song <baohua@kernel.org> Cc: Anshuman Khandual <anshuman.khandual@arm.com> Cc: Kefeng Wang <wangkefeng.wang@huawei.com> Cc: Kevin Brodsky <kevin.brodsky@arm.com> Cc: Yin Fengwei <fengwei_yin@linux.alibaba.com> Cc: linux-arm-kernel@lists.infradead.org Cc: linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
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.