lk/linux-kernel-test
1
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity

MIPS: Fix machine check exception in kmap_coherent()

Browse Source 
On an SMP system with cache aliases, the following sequence of events may
happen:

1) copy_user_highpage() runs on CPU0, invoking kmap_coherent() to create a
   temporary mapping in the fixmap region
2) copy_page() starts on CPU0
3) CPU1 sends CPU0 an IPI asking CPU0 to run local_r4k_flush_cache_page()
4) CPU0 takes the interrupt, interrupting copy_page()
5) local_r4k_flush_cache_page() on CPU0 calls kmap_coherent() again
6) The second invocation of kmap_coherent() on CPU0 tries to use the
   same fixmap virtual address that was being used by copy_user_highpage()
7) CPU0 throws a machine check exception for the TLB address conflict

Fixed by creating an extra set of fixmap entries for use in interrupt
handlers.  This prevents fixmap VA conflicts between copy_user_highpage()
running in user context, and local_r4k_flush_cache_page() invoked from an
SMP IPI.

Signed-off-by: Kevin Cernekee <cernekee@gmail.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
This commit is contained in:
Kevin Cernekee
2009-09-07 11:11:31 -07:00
committed by Ralf Baechle
parent 39d2211d20
commit 0f334a3e8c
2 changed files with 7 additions and 3 deletions
Download Patch File Download Diff File Expand all files Collapse all files

4
arch/mips/include/asm/fixmap.h
View File

@@ -48,9 +48,9 @@ enum fixed_addresses {
#define FIX_N_COLOURS 8
FIX_CMAP_BEGIN,
#ifdef CONFIG_MIPS_MT_SMTC
FIX_CMAP_END = FIX_CMAP_BEGIN + (FIX_N_COLOURS * NR_CPUS),
FIX_CMAP_END = FIX_CMAP_BEGIN + (FIX_N_COLOURS * NR_CPUS * 2),
#else
FIX_CMAP_END = FIX_CMAP_BEGIN + FIX_N_COLOURS,
FIX_CMAP_END = FIX_CMAP_BEGIN + (FIX_N_COLOURS * 2),
#endif
#ifdef CONFIG_HIGHMEM
/* reserved pte's for temporary kernel mappings */