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 <mi...@kernel.org>
AuthorDate: Thu, 06 Aug 2020 15:11:03 +02:00
Committer: Ingo Molnar <mi...@kernel.org>
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" <ja...@zx2c4.com>
Analyzed-by: Linus Torvalds <torva...@linux-foundation.org>
Cc: Joerg Roedel <jroe...@suse.de>
Signed-off-by: Ingo Molnar <mi...@kernel.org>
---
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.
