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authorTony Luck <tony.luck@intel.com>2018-01-25 14:23:48 -0800
committerIngo Molnar <mingo@kernel.org>2018-02-13 16:25:06 +0100
commitfd0e786d9d09024f67bd71ec094b110237dc3840 (patch)
treeeff5acbc6ccf20e160d96cf0a608b27d438eb754 /mm/memory-failure.c
parentx86/error_inject: Make just_return_func() globally visible (diff)
downloadlinux-dev-fd0e786d9d09024f67bd71ec094b110237dc3840.tar.xz
linux-dev-fd0e786d9d09024f67bd71ec094b110237dc3840.zip
x86/mm, mm/hwpoison: Don't unconditionally unmap kernel 1:1 pages
In the following commit: ce0fa3e56ad2 ("x86/mm, mm/hwpoison: Clear PRESENT bit for kernel 1:1 mappings of poison pages") ... we added code to memory_failure() to unmap the page from the kernel 1:1 virtual address space to avoid speculative access to the page logging additional errors. But memory_failure() may not always succeed in taking the page offline, especially if the page belongs to the kernel. This can happen if there are too many corrected errors on a page and either mcelog(8) or drivers/ras/cec.c asks to take a page offline. Since we remove the 1:1 mapping early in memory_failure(), we can end up with the page unmapped, but still in use. On the next access the kernel crashes :-( There are also various debug paths that call memory_failure() to simulate occurrence of an error. Since there is no actual error in memory, we don't need to map out the page for those cases. Revert most of the previous attempt and keep the solution local to arch/x86/kernel/cpu/mcheck/mce.c. Unmap the page only when: 1) there is a real error 2) memory_failure() succeeds. All of this only applies to 64-bit systems. 32-bit kernel doesn't map all of memory into kernel space. It isn't worth adding the code to unmap the piece that is mapped because nobody would run a 32-bit kernel on a machine that has recoverable machine checks. Signed-off-by: Tony Luck <tony.luck@intel.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Andy Lutomirski <luto@kernel.org> Cc: Borislav Petkov <bp@suse.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Dave <dave.hansen@intel.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Robert (Persistent Memory) <elliott@hpe.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: linux-mm@kvack.org Cc: stable@vger.kernel.org #v4.14 Fixes: ce0fa3e56ad2 ("x86/mm, mm/hwpoison: Clear PRESENT bit for kernel 1:1 mappings of poison pages") Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to '')
-rw-r--r--mm/memory-failure.c2
1 files changed, 0 insertions, 2 deletions
diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 4b80ccee4535..8291b75f42c8 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -1139,8 +1139,6 @@ int memory_failure(unsigned long pfn, int flags)
return 0;
}
- arch_unmap_kpfn(pfn);
-
orig_head = hpage = compound_head(p);
num_poisoned_pages_inc();