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Commit 0c4888ef authored by Benjamin Herrenschmidt's avatar Benjamin Herrenschmidt
Browse files

powerpc: Fix fatal SLB miss when restoring PPR 



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: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
parent 36954dc7

arch/powerpc/include/asm/ppc_asm.h

+0 −7
Original line number Diff line number Diff line
@@ -406,13 +406,6 @@ 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



/*

arch/powerpc/kernel/entry_64.S

+9 −1
Original line number Diff line number Diff line
@@ -818,6 +818,12 @@ 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,
@@ -838,8 +844,10 @@ 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