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83ab598362
The NIOS2 hardware does not support conflicting mappings for the same virtual address (see Nios II Processor Reference Guide from 2023.08.28): "The operating system software is responsible for guaranteeing that multiple TLB entries do not map the same virtual address. The hardware behavior is undefined when multiple entries map the same virtual address." When flushing tlb-entries, the kernel may violate this invariant for virtual addresses related to PID 0 as flushing is currently implemented by assigning physical address, pid and flags to 0. A small example: Before flushing TLB mappings for pid:0x42: dump tlb-entries for line=0xd (addr 000d0000): -- way:09 vpn:0x0006d000 phys:0x01145000 pid:0x00 flags:rw--c ... -- way:0d vpn:0x0006d000 phys:0x02020000 pid:0x42 flags:rw--c After flushing TLB mappings for pid:0x42: dump tlb-entries for line=0xd (addr 000d0000): -- way:09 vpn:0x0006d000 phys:0x01145000 pid:0x00 flags:rw--c ... -- way:0d vpn:0x0006d000 phys:0x00000000 pid:0x00 flags:----- As functions such as replace_tlb_one_pid operate on the assumption of unique mappings, this can cause repeated pagefaults for a single address that are not covered by the existing spurious pagefault handling. This commit fixes this issue by keeping the pid field of the entries when flushing. That way, no conflicting mappings are introduced as the pair of <address,pid> is now kept unique: Fixed example after flushing TLB mappings for pid:0x42: dump tlb-entries for line=0xd (addr 000d0000): -- way:09 vpn:0x0006d000 phys:0x01145000 pid:0x00 flags:rw--c ... -- way:0d vpn:0x0006d000 phys:0x00000000 pid:0x42 flags:----- When flushing the complete tlb/initialising all entries, the way is used as a substitute mmu pid value for the "invalid" entries. Signed-off-by: Simon Schuster <schuster.simon@siemens-energy.com> Signed-off-by: Andreas Oetken <andreas.oetken@siemens-energy.com> Signed-off-by: Dinh Nguyen <dinguyen@kernel.org> |
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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.