linux/arch/mips/include/asm/cacheflush.h

153 lines
4.9 KiB

MIPS: Fix race condition in lazy cache flushing. The lazy cache flushing implemented in the MIPS kernel suffers from a race condition that is exposed by do_set_pte() in mm/memory.c. A pre-condition is a file-system that writes to the page from the CPU in its readpage method and then calls flush_dcache_page(). One example is ubifs. Another pre-condition is that the dcache flush is postponed in __flush_dcache_page(). Upon a page fault for an executable mapping not existing in the page-cache, the following will happen: 1. Write to the page 2. flush_dcache_page 3. flush_icache_page 4. set_pte_at 5. update_mmu_cache (commits the flush of a dcache-dirty page) Between steps 4 and 5 another thread can hit the same page and it will encounter a valid pte. Because the data still is in the L1 dcache the CPU will fetch stale data from L2 into the icache and execute garbage. This fix moves the commit of the cache flush to step 3 to close the race window. It also reduces the amount of flushes on non-executable mappings because we never enter __flush_dcache_page() for non-aliasing CPUs. Regressions can occur in drivers that mistakenly relies on the flush_dcache_page() in get_user_pages() for DMA operations. [ralf@linux-mips.org: Folded in patch 9346 to fix highmem issue.] Signed-off-by: Lars Persson <larper@axis.com> Cc: linux-mips@linux-mips.org Cc: paul.burton@imgtec.com Cc: linux-kernel@vger.kernel.org Patchwork: https://patchwork.linux-mips.org/patch/9346/ Patchwork: https://patchwork.linux-mips.org/patch/9738/ Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
2015-02-26 14:16:03 +01:00
MIPS: Fix race condition in lazy cache flushing. The lazy cache flushing implemented in the MIPS kernel suffers from a race condition that is exposed by do_set_pte() in mm/memory.c. A pre-condition is a file-system that writes to the page from the CPU in its readpage method and then calls flush_dcache_page(). One example is ubifs. Another pre-condition is that the dcache flush is postponed in __flush_dcache_page(). Upon a page fault for an executable mapping not existing in the page-cache, the following will happen: 1. Write to the page 2. flush_dcache_page 3. flush_icache_page 4. set_pte_at 5. update_mmu_cache (commits the flush of a dcache-dirty page) Between steps 4 and 5 another thread can hit the same page and it will encounter a valid pte. Because the data still is in the L1 dcache the CPU will fetch stale data from L2 into the icache and execute garbage. This fix moves the commit of the cache flush to step 3 to close the race window. It also reduces the amount of flushes on non-executable mappings because we never enter __flush_dcache_page() for non-aliasing CPUs. Regressions can occur in drivers that mistakenly relies on the flush_dcache_page() in get_user_pages() for DMA operations. [ralf@linux-mips.org: Folded in patch 9346 to fix highmem issue.] Signed-off-by: Lars Persson <larper@axis.com> Cc: linux-mips@linux-mips.org Cc: paul.burton@imgtec.com Cc: linux-kernel@vger.kernel.org Patchwork: https://patchwork.linux-mips.org/patch/9346/ Patchwork: https://patchwork.linux-mips.org/patch/9738/ Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
2015-02-26 14:16:03 +01:00
MIPS: Fix race condition in lazy cache flushing. The lazy cache flushing implemented in the MIPS kernel suffers from a race condition that is exposed by do_set_pte() in mm/memory.c. A pre-condition is a file-system that writes to the page from the CPU in its readpage method and then calls flush_dcache_page(). One example is ubifs. Another pre-condition is that the dcache flush is postponed in __flush_dcache_page(). Upon a page fault for an executable mapping not existing in the page-cache, the following will happen: 1. Write to the page 2. flush_dcache_page 3. flush_icache_page 4. set_pte_at 5. update_mmu_cache (commits the flush of a dcache-dirty page) Between steps 4 and 5 another thread can hit the same page and it will encounter a valid pte. Because the data still is in the L1 dcache the CPU will fetch stale data from L2 into the icache and execute garbage. This fix moves the commit of the cache flush to step 3 to close the race window. It also reduces the amount of flushes on non-executable mappings because we never enter __flush_dcache_page() for non-aliasing CPUs. Regressions can occur in drivers that mistakenly relies on the flush_dcache_page() in get_user_pages() for DMA operations. [ralf@linux-mips.org: Folded in patch 9346 to fix highmem issue.] Signed-off-by: Lars Persson <larper@axis.com> Cc: linux-mips@linux-mips.org Cc: paul.burton@imgtec.com Cc: linux-kernel@vger.kernel.org Patchwork: https://patchwork.linux-mips.org/patch/9346/ Patchwork: https://patchwork.linux-mips.org/patch/9738/ Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
2015-02-26 14:16:03 +01:00
[MIPS] Retire flush_icache_page from mm use. On the 34K the redundant cache operations were causing excessive stalls resulting in realtime code running on the second VPE missing its deadline. For all other platforms this patch is just a significant performance improvment as illustrated by below benchmark numbers. Processor, Processes - times in microseconds - smaller is better ------------------------------------------------------------------------------ Host OS Mhz null null open slct sig sig fork exec sh call I/O stat clos TCP inst hndl proc proc proc --------- ------------- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- 25Kf 2.6.18-rc4 533 0.49 1.16 7.57 33.4 30.5 1.34 12.4 5497 17.K 54.K 25Kf 2.6.18-rc4-p 533 0.49 1.16 6.68 23.0 30.7 1.36 8.55 5030 16.K 48.K 4Kc 2.6.18-rc4 80 4.21 15.0 131. 289. 261. 16.5 258. 18.K 70.K 227K 4Kc 2.6.18-rc4-p 80 4.34 13.1 128. 285. 262. 18.2 258. 12.K 52.K 176K 34Kc 2.6.18-rc4 40 5.01 14.0 61.6 90.0 477. 17.9 94.7 29.K 108K 342K 34Kc 2.6.18-rc4-p 40 4.98 13.9 61.2 89.7 475. 17.6 93.7 8758 44.K 158K BCM1480 2.6.18-rc4 700 0.28 0.60 3.68 5.92 16.0 0.78 5.08 931. 3163 15.K BCM1480 2.6.18-rc4-p 700 0.28 0.61 3.65 5.85 16.0 0.79 5.20 395. 1464 8385 TX49-16K 2.6.18-rc3 197 0.73 2.41 19.0 37.8 82.9 2.94 17.5 4438 14.K 56.K TX49-16K 2.6.18-rc3-p 197 0.73 2.40 19.9 36.3 82.9 2.94 23.4 2577 9103 38.K TX49-32K 2.6.18-rc3 396 0.36 1.19 6.80 11.8 41.0 1.46 8.17 2738 8465 32.K TX49-32K 2.6.18-rc3-p 396 0.36 1.19 6.82 10.2 41.0 1.46 8.18 1330 4638 18.K Original patch by me with enhancements by Atsushi Nemoto. Signed-off-by: Ralf Baechle <ralf@linux-mips.org> Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
2006-08-12 16:40:08 +01:00