From 67dd5a25f4efbfccf973159429cb20acdc5b0e0e Mon Sep 17 00:00:00 2001 From: Jeremy Fitzhardinge Date: Fri, 5 Oct 2007 17:19:35 -0700 Subject: [PATCH] xen: disable split pte locks for now When pinning and unpinning pagetables, we must protect them against being used by other CPUs, lest they see the pagetable in an intermediate read-only-but-not-pinned state. When using split pte locks, doing this properly would require taking all the pte locks for the pagetable while pinning, but this may overflow the PREEMPT_BITS part of the preempt counter if the process has mapped more than about 512M of memory. However, failing to take the pte locks causes write-protect faults when the pageout code is trying to clear the Access bit on a pte which is part of a freshy created and still being pinned process after fork. This is a short-term fix until the problem is solved properly. Signed-off-by: Jeremy Fitzhardinge Acked-by: Rik van Riel Acked-by: Hugh Dickins Cc: David Rientjes Cc: Andrew Morton Cc: Andi Kleen Cc: Keir Fraser Cc: Jan Beulich Signed-off-by: Linus Torvalds --- mm/Kconfig | 1 + 1 file changed, 1 insertion(+) diff --git a/mm/Kconfig b/mm/Kconfig index e24d348083c3..a7609cbcb00d 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -137,6 +137,7 @@ config SPLIT_PTLOCK_CPUS int default "4096" if ARM && !CPU_CACHE_VIPT default "4096" if PARISC && !PA20 + default "4096" if XEN default "4" # -- GitLab