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authorLinus Torvalds <torvalds@linux-foundation.org>2020-08-06 22:02:58 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2020-08-06 22:02:58 +0300
commit7b4ea9456dd3f73238408126ab00f1d906963d81 (patch)
treee7acb558ee7e2eb8d3cc1035377742b0f82e2d7f /kernel/locking
parent6d2b84a4e5b954bd2587e06c29577256f59e0030 (diff)
downloadlinux-7b4ea9456dd3f73238408126ab00f1d906963d81.tar.xz
Revert "x86/mm/64: Do not sync vmalloc/ioremap mappings"
This reverts commit 8bb9bf242d1fee925636353807c511d54fde8986. It seems the vmalloc page tables aren't always preallocated in all situations, because Jason Donenfeld reports an oops with this commit: BUG: unable to handle page fault for address: ffffe8ffffd00608 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 0 P4D 0 Oops: 0000 [#1] PREEMPT SMP CPU: 2 PID: 22 Comm: kworker/2:0 Not tainted 5.8.0+ #154 RIP: process_one_work+0x2c/0x2d0 Code: 41 56 41 55 41 54 55 48 89 f5 53 48 89 fb 48 83 ec 08 48 8b 06 4c 8b 67 40 49 89 c6 45 30 f6 a8 04 b8 00 00 00 00 4c 0f 44 f0 <49> 8b 46 08 44 8b a8 00 01 05 Call Trace: worker_thread+0x4b/0x3b0 ? rescuer_thread+0x360/0x360 kthread+0x116/0x140 ? __kthread_create_worker+0x110/0x110 ret_from_fork+0x1f/0x30 CR2: ffffe8ffffd00608 and that page fault address is right in that vmalloc space, and we clearly don't have a PGD/P4D entry for it. Looking at the "Code:" line, the actual fault seems to come from the 'pwq->wq' dereference at the top of the process_one_work() function: struct pool_workqueue *pwq = get_work_pwq(work); struct worker_pool *pool = worker->pool; bool cpu_intensive = pwq->wq->flags & WQ_CPU_INTENSIVE; so 'struct pool_workqueue *pwq' is the allocation that hasn't been synchronized across CPUs. Just revert for now, while Joerg figures out the cause. Reported-and-bisected-by: Jason A. Donenfeld <Jason@zx2c4.com> Acked-by: Ingo Molnar <mingo@kernel.org> Acked-by: Joerg Roedel <jroedel@suse.de> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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