From 7b4ea9456dd3f73238408126ab00f1d906963d81 Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Thu, 6 Aug 2020 12:02:58 -0700 Subject: [PATCH] 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 Acked-by: Ingo Molnar Acked-by: Joerg Roedel Signed-off-by: Linus Torvalds --- arch/x86/include/asm/pgtable_64_types.h | 2 ++ arch/x86/mm/init_64.c | 5 +++++ 2 files changed, 7 insertions(+) diff --git a/arch/x86/include/asm/pgtable_64_types.h b/arch/x86/include/asm/pgtable_64_types.h index 52e5f5f..8f63efb 100644 --- a/arch/x86/include/asm/pgtable_64_types.h +++ b/arch/x86/include/asm/pgtable_64_types.h @@ -159,4 +159,6 @@ extern unsigned int ptrs_per_p4d; #define PGD_KERNEL_START ((PAGE_SIZE / 2) / sizeof(pgd_t)) +#define ARCH_PAGE_TABLE_SYNC_MASK (pgtable_l5_enabled() ? PGTBL_PGD_MODIFIED : PGTBL_P4D_MODIFIED) + #endif /* _ASM_X86_PGTABLE_64_DEFS_H */ diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c index e65b96f..3f4e29a 100644 --- a/arch/x86/mm/init_64.c +++ b/arch/x86/mm/init_64.c @@ -217,6 +217,11 @@ static void sync_global_pgds(unsigned long start, unsigned long end) sync_global_pgds_l4(start, end); } +void arch_sync_kernel_mappings(unsigned long start, unsigned long end) +{ + sync_global_pgds(start, end); +} + /* * NOTE: This function is marked __ref because it calls __init function * (alloc_bootmem_pages). It's safe to do it ONLY when after_bootmem == 0. -- 2.7.4