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Commit e9500dd8 authored by Max Filippov's avatar Max Filippov
Browse files

xtensa: make fast_unaligned store restartable 



fast_unaligned may encounter DTLB miss or SEGFAULT during the store
emulation. Don't update epc1 and lcount until after the store emulation
is complete, so that the faulting store instruction could be replayed.
Remove duplicate code handling zero overhead loops and calculate new
epc1 and lcount in one place.

Signed-off-by: default avatarMax Filippov <jcmvbkbc@gmail.com>
parent c3ef1f4d

arch/xtensa/kernel/align.S

+19 −32
Original line number Diff line number Diff line
@@ -277,18 +277,6 @@ ENTRY(fast_unaligned) 
	/* Set target register. */



1:



#if XCHAL_HAVE_LOOPS

	rsr	a5, lend		# check if we reached LEND

	bne	a7, a5, 1f

	rsr	a5, lcount		# and LCOUNT != 0

	beqz	a5, 1f

	addi	a5, a5, -1		# decrement LCOUNT and set

	rsr	a7, lbeg		# set PC to LBEGIN

	wsr	a5, lcount

#endif



1:	wsr	a7, epc1		# skip load instruction

	extui	a4, a4, INSN_T, 4	# extract target register

	movi	a5, .Lload_table

	addx8	a4, a4, a5
@@ -358,17 +346,6 @@ ENTRY(fast_unaligned) 
	/* Get memory address */



1:

#if XCHAL_HAVE_LOOPS

	rsr	a4, lend		# check if we reached LEND

	bne	a7, a4, 1f

	rsr	a4, lcount		# and LCOUNT != 0

	beqz	a4, 1f

	addi	a4, a4, -1		# decrement LCOUNT and set

	rsr	a7, lbeg		# set PC to LBEGIN

	wsr	a4, lcount

#endif



1:	wsr	a7, epc1		# skip store instruction

	movi	a4, ~3

	and	a4, a4, a8		# align memory address
@@ -380,25 +357,25 @@ ENTRY(fast_unaligned) 
#endif



	__ssa8r a8

	__src_b	a7, a5, a6		# lo-mask  F..F0..0 (BE) 0..0F..F (LE)

	__src_b	a8, a5, a6		# lo-mask  F..F0..0 (BE) 0..0F..F (LE)

	__src_b	a6, a6, a5		# hi-mask  0..0F..F (BE) F..F0..0 (LE)

#ifdef UNALIGNED_USER_EXCEPTION

	l32e	a5, a4, -8

#else

	l32i	a5, a4, 0		# load lower address word

#endif

	and	a5, a5, a7		# mask

	__sh	a7, a3 			# shift value

	or	a5, a5, a7		# or with original value

	and	a5, a5, a8		# mask

	__sh	a8, a3 			# shift value

	or	a5, a5, a8		# or with original value

#ifdef UNALIGNED_USER_EXCEPTION

	s32e	a5, a4, -8

	l32e	a7, a4, -4

	l32e	a8, a4, -4

#else

	s32i	a5, a4, 0		# store

	l32i	a7, a4, 4		# same for upper address word

	l32i	a8, a4, 4		# same for upper address word

#endif

	__sl	a5, a3

	and	a6, a7, a6

	and	a6, a8, a6

	or	a6, a6, a5

#ifdef UNALIGNED_USER_EXCEPTION

	s32e	a6, a4, -4
@@ -406,9 +383,19 @@ ENTRY(fast_unaligned) 
	s32i	a6, a4, 4

#endif



	/* Done. restore stack and return */



.Lexit:

#if XCHAL_HAVE_LOOPS

	rsr	a4, lend		# check if we reached LEND

	bne	a7, a4, 1f

	rsr	a4, lcount		# and LCOUNT != 0

	beqz	a4, 1f

	addi	a4, a4, -1		# decrement LCOUNT and set

	rsr	a7, lbeg		# set PC to LBEGIN

	wsr	a4, lcount

#endif



1:	wsr	a7, epc1		# skip emulated instruction



	movi	a4, 0

	rsr	a3, excsave1

	s32i	a4, a3, EXC_TABLE_FIXUP