kernel/linux.git/arch/xtensa/mm/fault.c, branch linux-7.0.y

xtensa: fault: include

2023-09-20T12:03:18+00:00

Use to provide the function prototype for do_page_fault() to prevent a build warning: arch/xtensa/mm/fault.c:87:6: warning: no previous prototype for 'do_page_fault' [-Wmissing-prototypes] 87 | void do_page_fault(struct pt_regs *regs) Signed-off-by: Randy Dunlap Cc: Chris Zankel Cc: Max Filippov Message-Id: <20230920052139.10570-3-rdunlap@infradead.org> Signed-off-by: Max Filippov

mm/fault: convert remaining simple cases to lock_mm_and_find_vma()

2023-06-24T21:12:58+00:00

This does the simple pattern conversion of alpha, arc, csky, hexagon, loongarch, nios2, sh, sparc32, and xtensa to the lock_mm_and_find_vma() helper. They all have the regular fault handling pattern without odd special cases. The remaining architectures all have something that keeps us from a straightforward conversion: ia64 and parisc have stacks that can grow both up as well as down (and ia64 has special address region checks). And m68k, microblaze, openrisc, sparc64, and um end up having extra rules about only expanding the stack down a limited amount below the user space stack pointer. That is something that x86 used to do too (long long ago), and it probably could just be skipped, but it still makes the conversion less than trivial. Note that this conversion was done manually and with the exception of alpha without any build testing, because I have a fairly limited cross- building environment. The cases are all simple, and I went through the changes several times, but... Signed-off-by: Linus Torvalds

xtensa: drop unused members of struct thread_struct

2023-01-07T07:33:11+00:00

bad_vaddr, bad_uaddr and error_code fields are set but never read by the xtensa arch-specific code. Drop them. Also drop the commented out info field. Signed-off-by: Max Filippov

mm: avoid unnecessary page fault retires on shared memory types

2022-06-17T02:48:27+00:00

I observed that for each of the shared file-backed page faults, we're very likely to retry one more time for the 1st write fault upon no page. It's because we'll need to release the mmap lock for dirty rate limit purpose with balance_dirty_pages_ratelimited() (in fault_dirty_shared_page()). Then after that throttling we return VM_FAULT_RETRY. We did that probably because VM_FAULT_RETRY is the only way we can return to the fault handler at that time telling it we've released the mmap lock. However that's not ideal because it's very likely the fault does not need to be retried at all since the pgtable was well installed before the throttling, so the next continuous fault (including taking mmap read lock, walk the pgtable, etc.) could be in most cases unnecessary. It's not only slowing down page faults for shared file-backed, but also add more mmap lock contention which is in most cases not needed at all. To observe this, one could try to write to some shmem page and look at "pgfault" value in /proc/vmstat, then we should expect 2 counts for each shmem write simply because we retried, and vm event "pgfault" will capture that. To make it more efficient, add a new VM_FAULT_COMPLETED return code just to show that we've completed the whole fault and released the lock. It's also a hint that we should very possibly not need another fault immediately on this page because we've just completed it. This patch provides a ~12% perf boost on my aarch64 test VM with a simple program sequentially dirtying 400MB shmem file being mmap()ed and these are the time it needs: Before: 650.980 ms (+-1.94%) After: 569.396 ms (+-1.38%) I believe it could help more than that. We need some special care on GUP and the s390 pgfault handler (for gmap code before returning from pgfault), the rest changes in the page fault handlers should be relatively straightforward. Another thing to mention is that mm_account_fault() does take this new fault as a generic fault to be accounted, unlike VM_FAULT_RETRY. I explicitly didn't touch hmm_vma_fault() and break_ksm() because they do not handle VM_FAULT_RETRY even with existing code, so I'm literally keeping them as-is. Link: https://lkml.kernel.org/r/20220530183450.42886-1-peterx@redhat.com Signed-off-by: Peter Xu Acked-by: Geert Uytterhoeven Acked-by: Peter Zijlstra (Intel) Acked-by: Johannes Weiner Acked-by: Vineet Gupta Acked-by: Guo Ren Acked-by: Max Filippov Acked-by: Christian Borntraeger Acked-by: Michael Ellerman (powerpc) Acked-by: Catalin Marinas Reviewed-by: Alistair Popple Reviewed-by: Ingo Molnar Acked-by: Russell King (Oracle) [arm part] Acked-by: Heiko Carstens Cc: Vasily Gorbik Cc: Stafford Horne Cc: David S. Miller Cc: Johannes Berg Cc: Brian Cain Cc: Richard Henderson Cc: Richard Weinberger Cc: Benjamin Herrenschmidt Cc: Thomas Gleixner Cc: Janosch Frank Cc: Albert Ou Cc: Anton Ivanov Cc: Dave Hansen Cc: Borislav Petkov Cc: Sven Schnelle Cc: Andrea Arcangeli Cc: James Bottomley Cc: Al Viro Cc: Alexander Gordeev Cc: Jonas Bonn Cc: Will Deacon Cc: Vlastimil Babka Cc: Michal Simek Cc: Matt Turner Cc: Paul Mackerras Cc: David Hildenbrand Cc: Nicholas Piggin Cc: Palmer Dabbelt Cc: Stefan Kristiansson Cc: Paul Walmsley Cc: Ivan Kokshaysky Cc: Chris Zankel Cc: Hugh Dickins Cc: Dinh Nguyen Cc: Rich Felker Cc: H. Peter Anvin Cc: Andy Lutomirski Cc: Thomas Bogendoerfer Cc: Helge Deller Cc: Yoshinori Sato Signed-off-by: Andrew Morton

xtensa: noMMU: allow handling protection faults

2022-05-02T02:51:21+00:00

Many xtensa CPU cores without full MMU still have memory protection features capable of raising exceptions for invalid instruction fetches/data access. Allow handling such exceptions. This improves behavior of processes that pass invalid memory pointers to syscalls in noMMU configs: in case of exception the kernel instead of killing the process is now able to return -EINVAL from a syscall. Introduce CONFIG_PFAULT that controls whether protection fault code is enabled and register handlers for common memory protection exceptions when it is enabled. Signed-off-by: Max Filippov

xtensa: extract vmalloc_fault code into a function

2022-05-02T02:51:21+00:00

Move full MMU-specific code into a separate function to isolate it from more generic do_page_fault code. No functional changes. Signed-off-by: Max Filippov

xtensa: move asid_cache from fault.c to mmu.c

2022-05-02T02:51:20+00:00

asid_cache is only useful with full MMU, but fault.c is also useful with MPU. Move asid_cache definition to MMU-specific source file. Signed-off-by: Max Filippov

mm: remove redundant check about FAULT_FLAG_ALLOW_RETRY bit

2022-01-15T14:30:27+00:00

Since commit 4064b9827063 ("mm: allow VM_FAULT_RETRY for multiple times") allowed VM_FAULT_RETRY for multiple times, the FAULT_FLAG_ALLOW_RETRY bit of fault_flag will not be changed in the page fault path, so the following check is no longer needed: flags & FAULT_FLAG_ALLOW_RETRY So just remove it. [akpm@linux-foundation.org: coding style fixes] Link: https://lkml.kernel.org/r/20211110123358.36511-1-zhengqi.arch@bytedance.com Signed-off-by: Qi Zheng Cc: Peter Zijlstra Cc: Ingo Molnar Cc: David Hildenbrand Cc: Kirill Shutemov Cc: Peter Xu Cc: Muchun Song Cc: Chengming Zhou Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

exit: Remove calls of do_exit after noreturn versions of die

2021-10-20T18:09:47+00:00

On nds32, openrisc, s390, sh, and xtensa the function die never returns. Mark die __noreturn so that no one expects die to return. Remove the do_exit calls after die as they will never be reached. Cc: Jonas Bonn Cc: Stefan Kristiansson Cc: Stafford Horne Cc: openrisc@lists.librecores.org Cc: Nick Hu Cc: Greentime Hu Cc: Vincent Chen Cc: Heiko Carstens Cc: Vasily Gorbik Cc: Christian Borntraeger Cc: linux-s390@vger.kernel.org Cc: Yoshinori Sato Cc: Rich Felker Cc: linux-sh@vger.kernel.org Cc: linux-xtensa@linux-xtensa.org Cc: Chris Zankel Cc: Max Filippov Fixes: 2.3.16 Fixes: 2.3.99-pre8 Fixes: 3f65ce4d141e ("[PATCH] xtensa: Architecture support for Tensilica Xtensa Part 5") Fixes: 664eec400bf8 ("nds32: MMU fault handling and page table management") Fixes: 61e85e367535 ("OpenRISC: Memory management") Link: https://lkml.kernel.org/r/20211020174406.17889-2-ebiederm@xmission.com Signed-off-by: Eric W. Biederman

xtensa: fix uaccess-related livelock in do_page_fault

2021-03-29T18:25:11+00:00

If a uaccess (e.g. get_user()) triggers a fault and there's a fault signal pending, the handler will return to the uaccess without having performed a uaccess fault fixup, and so the CPU will immediately execute the uaccess instruction again, whereupon it will livelock bouncing between that instruction and the fault handler. https://lore.kernel.org/lkml/20210121123140.GD48431@C02TD0UTHF1T.local/ Cc: stable@vger.kernel.org Reported-by: Mark Rutland Signed-off-by: Max Filippov