From 74260714c56de4f967fcb2f17a8656bc574b75be Mon Sep 17 00:00:00 2001 From: Jeremy Fitzhardinge Date: Tue, 16 Oct 2007 11:51:30 -0700 Subject: xen: lock pte pages while pinning/unpinning When a pagetable is created, it is made globally visible in the rmap prio tree before it is pinned via arch_dup_mmap(), and remains in the rmap tree while it is unpinned with arch_exit_mmap(). This means that other CPUs may race with the pinning/unpinning process, and see a pte between when it gets marked RO and actually pinned, causing any pte updates to fail with write-protect faults. As a result, all pte pages must be properly locked, and only unlocked once the pinning/unpinning process has finished. In order to avoid taking spinlocks for the whole pagetable - which may overflow the PREEMPT_BITS portion of preempt counter - it locks and pins each pte page individually, and then finally pins the whole pagetable. Signed-off-by: Jeremy Fitzhardinge Cc: Rik van Riel Cc: Hugh Dickens Cc: David Rientjes Cc: Andrew Morton Cc: Andi Kleen Cc: Keir Fraser Cc: Jan Beulich --- mm/Kconfig | 1 - 1 file changed, 1 deletion(-) (limited to 'mm/Kconfig') diff --git a/mm/Kconfig b/mm/Kconfig index a7609cbcb00..e24d348083c 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -137,7 +137,6 @@ config SPLIT_PTLOCK_CPUS int default "4096" if ARM && !CPU_CACHE_VIPT default "4096" if PARISC && !PA20 - default "4096" if XEN default "4" # -- cgit v1.2.3