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Nadav Amit
8f1d56f64f
Commitaa44284960("x86/mm/tlb: Avoid reading mm_tlb_gen when possible") introduced an optimization to skip superfluous TLB flushes based on the generation provided in flush_tlb_info. However, arch_tlbbatch_flush() does not provide any generation in flush_tlb_info and populates the flush_tlb_info generation with 0. This 0 is causes the flush_tlb_info to be interpreted as a superfluous, old flush. As a result, try_to_unmap_one() would not perform any TLB flushes. Fix it by checking whether f->new_tlb_gen is nonzero. Zero value is anyhow is an invalid generation value. To avoid future confusion, introduce TLB_GENERATION_INVALID constant and use it properly. Add warnings to ensure no partial flushes are done with TLB_GENERATION_INVALID or when f->mm is NULL, since this does not make any sense. In addition, add the missing unlikely(). [ dhansen: change VM_BUG_ON() -> VM_WARN_ON(), clarify changelog ] Fixes:aa44284960("x86/mm/tlb: Avoid reading mm_tlb_gen when possible") Reported-by: Hugh Dickins <hughd@google.com> Signed-off-by: Nadav Amit <namit@vmware.com> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> Tested-by: Hugh Dickins <hughd@google.com> Link: https://lkml.kernel.org/r/20220710232837.3618-1-namit@vmware.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 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.