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Sachin reported a warning when running the inject-ra-err selftest: # selftests: powerpc/mce: inject-ra-err Disabling lock debugging due to kernel taint MCE: CPU19: machine check (Severe) Real address Load/Store (foreign/control memory) [Not recovered] MCE: CPU19: PID: 5254 Comm: inject-ra-err NIP: [0000000010000e48] MCE: CPU19: Initiator CPU MCE: CPU19: Unknown ------------[ cut here ]------------ WARNING: CPU: 19 PID: 5254 at arch/powerpc/mm/book3s64/radix_tlb.c:1221 radix__tlb_flush+0x160/0x180 CPU: 19 PID: 5254 Comm: inject-ra-err Kdump: loaded Tainted: G M E 6.6.0-rc3-00055-g9ed22ae6be81 #4 Hardware name: IBM,9080-HEX POWER10 (raw) 0x800200 0xf000006 of:IBM,FW1030.20 (NH1030_058) hv:phyp pSeries ... NIP radix__tlb_flush+0x160/0x180 LR radix__tlb_flush+0x104/0x180 Call Trace: radix__tlb_flush+0xf4/0x180 (unreliable) tlb_finish_mmu+0x15c/0x1e0 exit_mmap+0x1a0/0x510 __mmput+0x60/0x1e0 exit_mm+0xdc/0x170 do_exit+0x2bc/0x5a0 do_group_exit+0x4c/0xc0 sys_exit_group+0x28/0x30 system_call_exception+0x138/0x330 system_call_vectored_common+0x15c/0x2ec And bisected it to commite43c0a0c3c("powerpc/64s/radix: combine final TLB flush and lazy tlb mm shootdown IPIs"), which added a warning in radix__tlb_flush() if mm->context.copros is still elevated. However it's possible for the copros count to be elevated if a process exits without first closing file descriptors that are associated with a copro, eg. VAS. If the process exits with a VAS file still open, the release callback is queued up for exit_task_work() via: exit_files() put_files_struct() close_files() filp_close() fput() And called via: exit_task_work() ____fput() __fput() file->f_op->release(inode, file) coproc_release() vas_user_win_ops->close_win() vas_deallocate_window() mm_context_remove_vas_window() mm_context_remove_copro() But that is after exit_mm() has been called from do_exit() and triggered the warning. Fix it by dropping the warning, and always calling __flush_all_mm(). In the normal case of no copros, that will result in a call to _tlbiel_pid(mm->context.id, RIC_FLUSH_ALL) just as the current code does. If the copros count is elevated then it will cause a global flush, which should flush translations from any copros. Note that the process table entry was cleared in arch_exit_mmap(), so copros should not be able to fetch any new translations. Fixes:e43c0a0c3c("powerpc/64s/radix: combine final TLB flush and lazy tlb mm shootdown IPIs") Reported-by: Sachin Sant <sachinp@linux.ibm.com> Closes: https://lore.kernel.org/all/A8E52547-4BF1-47CE-8AEA-BC5A9D7E3567@linux.ibm.com/ Signed-off-by: Nicholas Piggin <npiggin@gmail.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Tested-by: Sachin Sant <sachinp@linux.ibm.com> Link: https://msgid.link/20231017121527.1574104-1-mpe@ellerman.id.au
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.