From cd94154cc6a28dd9dc271042c1a59c08d26da886 Mon Sep 17 00:00:00 2001 From: Martin Schwidefsky Date: Wed, 11 Apr 2012 14:28:07 +0200 Subject: [S390] fix tlb flushing for page table pages Git commit 36409f6353fc2d7b6516e631415f938eadd92ffa "use generic RCU page-table freeing code" introduced a tlb flushing bug. Partially revert the above git commit and go back to s390 specific page table flush code. For s390 the TLB can contain three types of entries, "normal" TLB page-table entries, TLB combined region-and-segment-table (CRST) entries and real-space entries. Linux does not use real-space entries which leaves normal TLB entries and CRST entries. The CRST entries are intermediate steps in the page-table translation called translation paths. For example a 4K page access in a three-level page table setup will create two CRST TLB entries and one page-table TLB entry. The advantage of that approach is that a page access next to the previous one can reuse the CRST entries and needs just a single read from memory to create the page-table TLB entry. The disadvantage is that the TLB flushing rules are more complicated, before any page-table may be freed the TLB needs to be flushed. In short: the generic RCU page-table freeing code is incorrect for the CRST entries, in particular the check for mm_users < 2 is troublesome. This is applicable to 3.0+ kernels. Cc: Signed-off-by: Martin Schwidefsky --- arch/s390/Kconfig | 1 - 1 file changed, 1 deletion(-) (limited to 'arch/s390/Kconfig') diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig index 2b7c0fbe578e..9015060919a0 100644 --- a/arch/s390/Kconfig +++ b/arch/s390/Kconfig @@ -90,7 +90,6 @@ config S390 select HAVE_KERNEL_XZ select HAVE_ARCH_MUTEX_CPU_RELAX select HAVE_ARCH_JUMP_LABEL if !MARCH_G5 - select HAVE_RCU_TABLE_FREE if SMP select ARCH_SAVE_PAGE_KEYS if HIBERNATION select HAVE_MEMBLOCK select HAVE_MEMBLOCK_NODE_MAP -- cgit v1.2.1