The following commit has been merged into the x86/urgent branch of tip: Commit-ID: f17506e2f14bfa8a6a2de9b8b6a3ccc6b6f7c9b6 Gitweb: https://git.kernel.org/tip/f17506e2f14bfa8a6a2de9b8b6a3ccc6b6f7c9b6 Author: Ingo Molnar <mingo@xxxxxxxxxx> AuthorDate: Thu, 06 Aug 2020 15:11:03 +02:00 Committer: Ingo Molnar <mingo@xxxxxxxxxx> CommitterDate: Thu, 06 Aug 2020 15:11:03 +02:00 Revert "x86/mm/64: Do not sync vmalloc/ioremap mappings" This reverts commit 8bb9bf242d1fee925636353807c511d54fde8986. Jason reported that this causes a new oops in process_one_work(), and bisected it to this commit. Linus suspects that it was caused by missing pagetable synchronization: > > 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 > > Yeah, missing page table because it wasn't copied. > > Presumably because that kthread is using the active_mm of some random > user space process that didn't get sync'ed. > > And the sync_global_pgds() may have ended up being sufficient > synchronization with whoever allocated thigns, even if it wasn't about > the TLB contents themselves. > > So apparently the "the page-table pages are all pre-allocated now" is > simply not true. Revert the commit for now. Reported-by: "Jason A. Donenfeld" <Jason@xxxxxxxxx> Analyzed-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Cc: Joerg Roedel <jroedel@xxxxxxx> Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx> --- 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.
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