From: Benjamin Herrenschmidt Date: Tue, 5 Nov 2013 05:33:22 +0000 (+1100) Subject: powerpc: Fix fatal SLB miss when restoring PPR X-Git-Tag: v3.12.15~142 X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=d30b39cb984459873b0fe79ba07a84e6e0c729d5;p=thirdparty%2Fkernel%2Fstable.git powerpc: Fix fatal SLB miss when restoring PPR 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 Signed-off-by: Jiri Slaby --- diff --git a/arch/powerpc/include/asm/ppc_asm.h b/arch/powerpc/include/asm/ppc_asm.h index 599545738af3e..c2dcfaa51987b 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 c04cdf70d4875..7be37170fda77 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