From 5843d9a4d0ba89719916c8f07fc9c57b7126be6d Mon Sep 17 00:00:00 2001 From: Nick Piggin Date: Fri, 1 Aug 2008 03:15:21 +0200 Subject: [PATCH] x86, pat: avoid highmem cache attribute aliasing Highmem code can leave ptes and tlb entries around for a given page even after kunmap, and after it has been freed. >From what I can gather, the PAT code may change the cache attributes of arbitrary physical addresses (ie. including highmem pages), which would result in aliases in the case that it operates on one of these lazy tlb highmem pages. Flushing kmaps should solve the problem. I've also just added code for conditional flushing if we haven't got any dangling highmem aliases -- this should help performance if we change page attributes frequently or systems that aren't using much highmem pages (eg. if < 4G RAM). Should be turned into 2 patches, but just for RFC... Signed-off-by: Ingo Molnar --- arch/x86/mm/pageattr.c | 3 +++ mm/highmem.c | 5 ++++- 2 files changed, 7 insertions(+), 1 deletion(-) diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c index 2c5c18c..4adb336 100644 --- a/arch/x86/mm/pageattr.c +++ b/arch/x86/mm/pageattr.c @@ -777,6 +777,9 @@ static int do_change_page_attr_set_clr(unsigned long addr, int numpages, WARN_ON_ONCE(1); } + /* Must avoid aliasing mappings in the highmem code */ + kmap_flush_unused(); + cpa.vaddr = addr; cpa.numpages = numpages; cpa.mask_set = mask_set; diff --git a/mm/highmem.c b/mm/highmem.c index e16e152..b36b83b 100644 --- a/mm/highmem.c +++ b/mm/highmem.c @@ -70,6 +70,7 @@ static DECLARE_WAIT_QUEUE_HEAD(pkmap_map_wait); static void flush_all_zero_pkmaps(void) { int i; + int need_flush = 0; flush_cache_kmaps(); @@ -101,8 +102,10 @@ static void flush_all_zero_pkmaps(void) &pkmap_page_table[i]); set_page_address(page, NULL); + need_flush = 1; } - flush_tlb_kernel_range(PKMAP_ADDR(0), PKMAP_ADDR(LAST_PKMAP)); + if (need_flush) + flush_tlb_kernel_range(PKMAP_ADDR(0), PKMAP_ADDR(LAST_PKMAP)); } /** -- 2.7.4