Messages in this thread Patch in this message | | | Date | Tue, 27 Jun 2017 00:19:10 -0700 | From | "tip-bot for Jérôme Glisse" <> | Subject | [tip:x86/urgent] x86/mm/hotplug: Fix BUG_ON() after hot-remove by not freeing PUD |
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Commit-ID: 98fe3633c5a44e5ee3d642907739eb0210407886 Gitweb: http://git.kernel.org/tip/98fe3633c5a44e5ee3d642907739eb0210407886 Author: Jérôme Glisse <jglisse@redhat.com> AuthorDate: Sat, 24 Jun 2017 14:05:14 -0400 Committer: Ingo Molnar <mingo@kernel.org> CommitDate: Mon, 26 Jun 2017 11:44:19 +0200
x86/mm/hotplug: Fix BUG_ON() after hot-remove by not freeing PUD
Since commit:
af2cf278ef4f ("x86/mm/hotplug: Don't remove PGD entries in remove_pagetable()")
we no longer free PUDs so that we do not have to synchronize all PGDs on hot-remove/vfree().
But the new 5-level page table patchset reverted that for 4-level page tables, in the following commit:
f2a6a7050109: ("x86: Convert the rest of the code to support p4d_t")
This patch restores the damage and disables free_pud() if we are in the 4-level page table case, thus avoiding BUG_ON() after hot-remove.
Signed-off-by: Jérôme Glisse <jglisse@redhat.com> [ Clarified the changelog and the code comments. ] Reviewed-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Andy Lutomirski <luto@kernel.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Logan Gunthorpe <logang@deltatee.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: linux-mm@kvack.org Link: http://lkml.kernel.org/r/20170624180514.3821-1-jglisse@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org> --- arch/x86/mm/init_64.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c index 95651dc..0a59daf 100644 --- a/arch/x86/mm/init_64.c +++ b/arch/x86/mm/init_64.c @@ -990,7 +990,13 @@ remove_p4d_table(p4d_t *p4d_start, unsigned long addr, unsigned long end, pud_base = pud_offset(p4d, 0); remove_pud_table(pud_base, addr, next, direct); - free_pud_table(pud_base, p4d); + /* + * For 4-level page tables we do not want to free PUDs, but in the + * 5-level case we should free them. This code will have to change + * to adapt for boot-time switching between 4 and 5 level page tables. + */ + if (CONFIG_PGTABLE_LEVELS == 5) + free_pud_table(pud_base, p4d); } if (direct)
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