From: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx> 3.12-stable review patch. If anyone has any objections, please let me know. =============== commit 0c4888ef1d8a8b82c29075ce7e257ff795af15c7 upstream. When restoring the PPR value, we incorrectly access the thread structure at a time where MSR:RI is clear, which means we cannot recover from nested faults. However the thread structure isn't covered by the "bolted" SLB entries and thus accessing can fault. This fixes it by splitting the code so that the PPR value is loaded into a GPR before MSR:RI is cleared. Signed-off-by: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx> Signed-off-by: Jiri Slaby <jslaby@xxxxxxx> --- arch/powerpc/include/asm/ppc_asm.h | 7 ------- arch/powerpc/kernel/entry_64.S | 10 +++++++++- 2 files changed, 9 insertions(+), 8 deletions(-) diff --git a/arch/powerpc/include/asm/ppc_asm.h b/arch/powerpc/include/asm/ppc_asm.h index 599545738af3..c2dcfaa51987 100644 --- a/arch/powerpc/include/asm/ppc_asm.h +++ b/arch/powerpc/include/asm/ppc_asm.h @@ -478,13 +478,6 @@ BEGIN_FTR_SECTION_NESTED(945) \ std ra,TASKTHREADPPR(rb); \ END_FTR_SECTION_NESTED(CPU_FTR_HAS_PPR,CPU_FTR_HAS_PPR,945) -#define RESTORE_PPR(ra, rb) \ -BEGIN_FTR_SECTION_NESTED(946) \ - ld ra,PACACURRENT(r13); \ - ld rb,TASKTHREADPPR(ra); \ - mtspr SPRN_PPR,rb; /* Restore PPR */ \ -END_FTR_SECTION_NESTED(CPU_FTR_HAS_PPR,CPU_FTR_HAS_PPR,946) - #endif /* diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S index c04cdf70d487..7be37170fda7 100644 --- a/arch/powerpc/kernel/entry_64.S +++ b/arch/powerpc/kernel/entry_64.S @@ -820,6 +820,12 @@ fast_exception_return: andi. r0,r3,MSR_RI beq- unrecov_restore + /* Load PPR from thread struct before we clear MSR:RI */ +BEGIN_FTR_SECTION + ld r2,PACACURRENT(r13) + ld r2,TASKTHREADPPR(r2) +END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR) + /* * Clear RI before restoring r13. If we are returning to * userspace and we take an exception after restoring r13, @@ -840,8 +846,10 @@ fast_exception_return: */ andi. r0,r3,MSR_PR beq 1f +BEGIN_FTR_SECTION + mtspr SPRN_PPR,r2 /* Restore PPR */ +END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR) ACCOUNT_CPU_USER_EXIT(r2, r4) - RESTORE_PPR(r2, r4) REST_GPR(13, r1) 1: mtspr SPRN_SRR1,r3 -- 1.9.0 -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html