tjh.dev / kernel
Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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MIPS: Avoid potential hazard on Context register

set_saved_sp reads Context register. Avoid reading stale value from
earlier incomplete write.

Issue found and fixed for head.S by Chris Dearman <chris@mips.com>.

Signed-off-by: Chris Dearman <chris@mips.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

Ralf Baechle c2ea1d56 cd847b78

+4
unified split
+3
arch/mips/include/asm/mmu_context.h
··· 16 16 #include <linux/smp.h> 17 17 #include <linux/slab.h> 18 18 #include <asm/cacheflush.h> 19 + #include <asm/hazards.h> 19 20 #include <asm/tlbflush.h> 20 21 #ifdef CONFIG_MIPS_MT_SMTC 21 22 #include <asm/mipsmtregs.h> ··· 37 36 #ifdef CONFIG_32BIT 38 37 #define TLBMISS_HANDLER_SETUP() \ 39 38 write_c0_context((unsigned long) smp_processor_id() << 25); \ 39 + back_to_back_c0_hazard(); \ 40 40 TLBMISS_HANDLER_SETUP_PGD(swapper_pg_dir) 41 41 #endif 42 42 #ifdef CONFIG_64BIT 43 43 #define TLBMISS_HANDLER_SETUP() \ 44 44 write_c0_context((unsigned long) smp_processor_id() << 26); \ 45 + back_to_back_c0_hazard(); \ 45 46 TLBMISS_HANDLER_SETUP_PGD(swapper_pg_dir) 46 47 #endif 47 48
+1
arch/mips/kernel/head.S
··· 191 191 /* Set the SP after an empty pt_regs. */ 192 192 PTR_LI sp, _THREAD_SIZE - 32 - PT_SIZE 193 193 PTR_ADDU sp, $28 194 + back_to_back_c0_hazard 194 195 set_saved_sp sp, t0, t1 195 196 PTR_SUBU sp, 4 * SZREG # init stack pointer 196 197