linux.git/arch/powerpc/kernel/traps.c, branch v5.14 Linux kernel source tree powerpc/interrupt: Do not call single_step_exception() from other exceptions 2021-08-12T12:22:57+00:00 Christophe Leroy christophe.leroy@csgroup.eu 2021-08-10T16:13:17+00:00 01fcac8e4dfc112f420dcaeb70056a74e326cacf single_step_exception() is called by emulate_single_step() which is called from (at least) alignment exception() handler and program_check_exception() handler. Redefine it as a regular __single_step_exception() which is called by both single_step_exception() handler and emulate_single_step() function. Fixes: 3a96570ffceb ("powerpc: convert interrupt handlers to use wrappers") Cc: stable@vger.kernel.org # v5.12+ Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> Reviewed-by: Nicholas Piggin <npiggin@gmail.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/aed174f5cbc06f2cf95233c071d8aac948e46043.1628611921.git.christophe.leroy@csgroup.eu 
single_step_exception() is called by emulate_single_step() which
is called from (at least) alignment exception() handler and
program_check_exception() handler.

Redefine it as a regular __single_step_exception() which is called
by both single_step_exception() handler and emulate_single_step()
function.

Fixes: 3a96570ffceb ("powerpc: convert interrupt handlers to use wrappers")
Cc: stable@vger.kernel.org # v5.12+
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/aed174f5cbc06f2cf95233c071d8aac948e46043.1628611921.git.christophe.leroy@csgroup.eu
powerpc/64s: avoid reloading (H)SRR registers if they are still valid 2021-06-24T14:06:55+00:00 Nicholas Piggin npiggin@gmail.com 2021-06-17T15:51:03+00:00 59dc5bfca0cb6a29db1a50847684eb5c19f8f400 When an interrupt is taken, the SRR registers are set to return to where it left off. Unless they are modified in the meantime, or the return address or MSR are modified, there is no need to reload these registers when returning from interrupt. Introduce per-CPU flags that track the validity of SRR and HSRR registers. These are cleared when returning from interrupt, when using the registers for something else (e.g., OPAL calls), when adjusting the return address or MSR of a context, and when context switching (which changes the return address and MSR). This improves the performance of interrupt returns. Signed-off-by: Nicholas Piggin <npiggin@gmail.com> [mpe: Fold in fixup patch from Nick] Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20210617155116.2167984-5-npiggin@gmail.com 
When an interrupt is taken, the SRR registers are set to return to where
it left off. Unless they are modified in the meantime, or the return
address or MSR are modified, there is no need to reload these registers
when returning from interrupt.

Introduce per-CPU flags that track the validity of SRR and HSRR
registers. These are cleared when returning from interrupt, when
using the registers for something else (e.g., OPAL calls), when
adjusting the return address or MSR of a context, and when context
switching (which changes the return address and MSR).

This improves the performance of interrupt returns.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
[mpe: Fold in fixup patch from Nick]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210617155116.2167984-5-npiggin@gmail.com
powerpc/traps: Start using PPC_RAW_xx() macros 2021-06-15T14:16:48+00:00 Christophe Leroy christophe.leroy@csgroup.eu 2021-05-20T10:23:10+00:00 deefd0ae990a689089ea1e4f5ad41799d63d4fd9 Start using PPC_RAW_xx() macros where relevant. PPC_INST_SYNC is used to both represent the 'sync' instruction and the family of synchronisation instructions. Keep it for the later, maybe we'll change the name in the future to avoid confusion. Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/0945c155d6cb113431185fc1296ac127359fe29b.1621506159.git.christophe.leroy@csgroup.eu 
Start using PPC_RAW_xx() macros where relevant.

PPC_INST_SYNC is used to both represent the 'sync' instruction and
the family of synchronisation instructions. Keep it for the later,
maybe we'll change the name in the future to avoid confusion.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/0945c155d6cb113431185fc1296ac127359fe29b.1621506159.git.christophe.leroy@csgroup.eu
powerpc/traps: Enhance readability for trap types 2021-04-17T12:20:19+00:00 Xiongwei Song sxwjean@gmail.com 2021-04-14T11:00:33+00:00 7153d4bf0b373428d0393c001019da4d0483fddb Define macros to list ppc interrupt types in interttupt.h, replace the reference of the trap hex values with these macros. Referred the hex numbers in arch/powerpc/kernel/exceptions-64e.S, arch/powerpc/kernel/exceptions-64s.S, arch/powerpc/kernel/head_*.S, arch/powerpc/kernel/head_booke.h and arch/powerpc/include/asm/kvm_asm.h. Signed-off-by: Xiongwei Song <sxwjean@gmail.com> [mpe: Resolve conflicts in nmi_disables_ftrace(), fix 40x build] Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/1618398033-13025-1-git-send-email-sxwjean@me.com 
Define macros to list ppc interrupt types in interttupt.h, replace the
reference of the trap hex values with these macros.

Referred the hex numbers in arch/powerpc/kernel/exceptions-64e.S,
arch/powerpc/kernel/exceptions-64s.S, arch/powerpc/kernel/head_*.S,
arch/powerpc/kernel/head_booke.h and arch/powerpc/include/asm/kvm_asm.h.

Signed-off-by: Xiongwei Song <sxwjean@gmail.com>
[mpe: Resolve conflicts in nmi_disables_ftrace(), fix 40x build]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/1618398033-13025-1-git-send-email-sxwjean@me.com
powerpc: remove partial register save logic 2021-04-14T13:04:44+00:00 Nicholas Piggin npiggin@gmail.com 2021-03-16T10:42:04+00:00 8dc7f0229b7892ccb23e19c9f30511c68cc0fdcc All subarchitectures always save all GPRs to pt_regs interrupt frames now. Remove FULL_REGS and associated bits. Signed-off-by: Nicholas Piggin <npiggin@gmail.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20210316104206.407354-11-npiggin@gmail.com 
All subarchitectures always save all GPRs to pt_regs interrupt frames
now. Remove FULL_REGS and associated bits.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210316104206.407354-11-npiggin@gmail.com
powerpc/64e/interrupt: NMI save irq soft-mask state in C 2021-04-14T13:04:20+00:00 Nicholas Piggin npiggin@gmail.com 2021-03-16T10:41:59+00:00 3db8aa10de9a478b3086db7894e0266def3d77af 64e non-maskable interrupts save the state of the irq soft-mask in asm. This can be done in C in interrupt wrappers as 64s does. I haven't been able to test this with qemu because it doesn't seem to cause FSL bookE WDT interrupts. This makes WatchdogException an NMI interrupt, which affects 32-bit as well (okay, or create a new handler?) Signed-off-by: Nicholas Piggin <npiggin@gmail.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20210316104206.407354-6-npiggin@gmail.com 
64e non-maskable interrupts save the state of the irq soft-mask in
asm. This can be done in C in interrupt wrappers as 64s does.

I haven't been able to test this with qemu because it doesn't seem
to cause FSL bookE WDT interrupts.

This makes WatchdogException an NMI interrupt, which affects 32-bit
as well (okay, or create a new handler?)

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210316104206.407354-6-npiggin@gmail.com
powerpc/uaccess: Remove __get/put_user_inatomic() 2021-04-03T10:21:41+00:00 Christophe Leroy christophe.leroy@csgroup.eu 2021-03-10T17:46:43+00:00 bad956b8fe1a8b3b634d596ed2023ec30726cdf1 Powerpc is the only architecture having _inatomic variants of __get_user() and __put_user() accessors. They were introduced by commit e68c825bb016 ("[POWERPC] Add inatomic versions of __get_user and __put_user"). Those variants expand to the _nosleep macros instead of expanding to the _nocheck macros. The only difference between the _nocheck and the _nosleep macros is the call to might_fault(). Since commit 662bbcb2747c ("mm, sched: Allow uaccess in atomic with pagefault_disable()"), __get/put_user() can be used in atomic parts of the code, therefore __get/put_user_inatomic() have become useless. Remove __get_user_inatomic() and __put_user_inatomic(). Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> Reviewed-by: Daniel Axtens <dja@axtens.net> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/1e5c895669e8d54a7810b62dc61eb111f33c2c37.1615398265.git.christophe.leroy@csgroup.eu 
Powerpc is the only architecture having _inatomic variants of
__get_user() and __put_user() accessors. They were introduced
by commit e68c825bb016 ("[POWERPC] Add inatomic versions of __get_user
and __put_user").

Those variants expand to the _nosleep macros instead of expanding
to the _nocheck macros. The only difference between the _nocheck
and the _nosleep macros is the call to might_fault().

Since commit 662bbcb2747c ("mm, sched: Allow uaccess in atomic with
pagefault_disable()"), __get/put_user() can be used in atomic parts
of the code, therefore __get/put_user_inatomic() have become useless.

Remove __get_user_inatomic() and __put_user_inatomic().

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Reviewed-by: Daniel Axtens <dja@axtens.net>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/1e5c895669e8d54a7810b62dc61eb111f33c2c37.1615398265.git.christophe.leroy@csgroup.eu
powerpc/math: Fix missing __user qualifier for get_user() and other sparse warnings 2021-03-29T02:22:12+00:00 Christophe Leroy christophe.leroy@csgroup.eu 2021-03-15T12:00:09+00:00 e448e1e774dc0ca307c17e961daf7ede2e635c57 Sparse reports the following problems: arch/powerpc/math-emu/math.c:228:21: warning: Using plain integer as NULL pointer arch/powerpc/math-emu/math.c:228:31: warning: Using plain integer as NULL pointer arch/powerpc/math-emu/math.c:228:41: warning: Using plain integer as NULL pointer arch/powerpc/math-emu/math.c:228:51: warning: Using plain integer as NULL pointer arch/powerpc/math-emu/math.c:237:13: warning: incorrect type in initializer (different address spaces) arch/powerpc/math-emu/math.c:237:13: expected unsigned int [noderef] __user *_gu_addr arch/powerpc/math-emu/math.c:237:13: got unsigned int [usertype] * arch/powerpc/math-emu/math.c:226:1: warning: symbol 'do_mathemu' was not declared. Should it be static? Add missing __user qualifier when casting pointer used in get_user() Use NULL instead of 0 to initialise opX local variables. Add a prototype for do_mathemu() (Added in processor.h like sparc) Reported-by: kernel test robot <lkp@intel.com> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/e4d1aae7604d89c98a52dfd8ce8443462e595670.1615809591.git.christophe.leroy@csgroup.eu 
Sparse reports the following problems:

arch/powerpc/math-emu/math.c:228:21: warning: Using plain integer as NULL pointer
arch/powerpc/math-emu/math.c:228:31: warning: Using plain integer as NULL pointer
arch/powerpc/math-emu/math.c:228:41: warning: Using plain integer as NULL pointer
arch/powerpc/math-emu/math.c:228:51: warning: Using plain integer as NULL pointer
arch/powerpc/math-emu/math.c:237:13: warning: incorrect type in initializer (different address spaces)
arch/powerpc/math-emu/math.c:237:13:    expected unsigned int [noderef] __user *_gu_addr
arch/powerpc/math-emu/math.c:237:13:    got unsigned int [usertype] *
arch/powerpc/math-emu/math.c:226:1: warning: symbol 'do_mathemu' was not declared. Should it be static?

Add missing __user qualifier when casting pointer used in get_user()

Use NULL instead of 0 to initialise opX local variables.

Add a prototype for do_mathemu() (Added in processor.h like sparc)

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/e4d1aae7604d89c98a52dfd8ce8443462e595670.1615809591.git.christophe.leroy@csgroup.eu
powerpc/32: Remove ksp_limit 2021-03-29T02:22:05+00:00 Christophe Leroy christophe.leroy@csgroup.eu 2021-03-12T12:50:21+00:00 5747230645562921b5bc19f6409f7af08fe17c6d ksp_limit is there to help detect stack overflows. That is specific to ppc32 as it was removed from ppc64 in commit cbc9565ee826 ("powerpc: Remove ksp_limit on ppc64"). There are other means for detecting stack overflows. As ppc64 has proven to not need it, ppc32 should be able to do without it too. Lets remove it and simplify exception handling. Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/d789c3385b22e07bedc997613c0d26074cb513e7.1615552866.git.christophe.leroy@csgroup.eu 
ksp_limit is there to help detect stack overflows.
That is specific to ppc32 as it was removed from ppc64 in
commit cbc9565ee826 ("powerpc: Remove ksp_limit on ppc64").

There are other means for detecting stack overflows.

As ppc64 has proven to not need it, ppc32 should be able to do
without it too.

Lets remove it and simplify exception handling.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/d789c3385b22e07bedc997613c0d26074cb513e7.1615552866.git.christophe.leroy@csgroup.eu
powerpc/traps: Declare unrecoverable_exception() as __noreturn 2021-03-29T02:22:02+00:00 Christophe Leroy christophe.leroy@csgroup.eu 2021-03-12T12:50:10+00:00 a58cbed68315111c663f35603a42547f72acd6f8 unrecoverable_exception() is never expected to return, most callers have an infiniteloop in case it returns. Ensure it really never returns by terminating it with a BUG(), and declare it __no_return. It always GCC to really simplify functions calling it. In the exemple below, it avoids the stack frame in the likely fast path and avoids code duplication for the exit. With this patch: 00000348 <interrupt_exit_kernel_prepare>: 348: 81 43 00 84 lwz r10,132(r3) 34c: 71 48 00 02 andi. r8,r10,2 350: 41 82 00 2c beq 37c <interrupt_exit_kernel_prepare+0x34> 354: 71 4a 40 00 andi. r10,r10,16384 358: 40 82 00 20 bne 378 <interrupt_exit_kernel_prepare+0x30> 35c: 80 62 00 70 lwz r3,112(r2) 360: 74 63 00 01 andis. r3,r3,1 364: 40 82 00 28 bne 38c <interrupt_exit_kernel_prepare+0x44> 368: 7d 40 00 a6 mfmsr r10 36c: 7c 11 13 a6 mtspr 81,r0 370: 7c 12 13 a6 mtspr 82,r0 374: 4e 80 00 20 blr 378: 48 00 00 00 b 378 <interrupt_exit_kernel_prepare+0x30> 37c: 94 21 ff f0 stwu r1,-16(r1) 380: 7c 08 02 a6 mflr r0 384: 90 01 00 14 stw r0,20(r1) 388: 48 00 00 01 bl 388 <interrupt_exit_kernel_prepare+0x40> 388: R_PPC_REL24 unrecoverable_exception 38c: 38 e2 00 70 addi r7,r2,112 390: 3d 00 00 01 lis r8,1 394: 7c c0 38 28 lwarx r6,0,r7 398: 7c c6 40 78 andc r6,r6,r8 39c: 7c c0 39 2d stwcx. r6,0,r7 3a0: 40 a2 ff f4 bne 394 <interrupt_exit_kernel_prepare+0x4c> 3a4: 38 60 00 01 li r3,1 3a8: 4b ff ff c0 b 368 <interrupt_exit_kernel_prepare+0x20> Without this patch: 00000348 <interrupt_exit_kernel_prepare>: 348: 94 21 ff f0 stwu r1,-16(r1) 34c: 93 e1 00 0c stw r31,12(r1) 350: 7c 7f 1b 78 mr r31,r3 354: 81 23 00 84 lwz r9,132(r3) 358: 71 2a 00 02 andi. r10,r9,2 35c: 41 82 00 34 beq 390 <interrupt_exit_kernel_prepare+0x48> 360: 71 29 40 00 andi. r9,r9,16384 364: 40 82 00 28 bne 38c <interrupt_exit_kernel_prepare+0x44> 368: 80 62 00 70 lwz r3,112(r2) 36c: 74 63 00 01 andis. r3,r3,1 370: 40 82 00 3c bne 3ac <interrupt_exit_kernel_prepare+0x64> 374: 7d 20 00 a6 mfmsr r9 378: 7c 11 13 a6 mtspr 81,r0 37c: 7c 12 13 a6 mtspr 82,r0 380: 83 e1 00 0c lwz r31,12(r1) 384: 38 21 00 10 addi r1,r1,16 388: 4e 80 00 20 blr 38c: 48 00 00 00 b 38c <interrupt_exit_kernel_prepare+0x44> 390: 7c 08 02 a6 mflr r0 394: 90 01 00 14 stw r0,20(r1) 398: 48 00 00 01 bl 398 <interrupt_exit_kernel_prepare+0x50> 398: R_PPC_REL24 unrecoverable_exception 39c: 80 01 00 14 lwz r0,20(r1) 3a0: 81 3f 00 84 lwz r9,132(r31) 3a4: 7c 08 03 a6 mtlr r0 3a8: 4b ff ff b8 b 360 <interrupt_exit_kernel_prepare+0x18> 3ac: 39 02 00 70 addi r8,r2,112 3b0: 3d 40 00 01 lis r10,1 3b4: 7c e0 40 28 lwarx r7,0,r8 3b8: 7c e7 50 78 andc r7,r7,r10 3bc: 7c e0 41 2d stwcx. r7,0,r8 3c0: 40 a2 ff f4 bne 3b4 <interrupt_exit_kernel_prepare+0x6c> 3c4: 38 60 00 01 li r3,1 3c8: 4b ff ff ac b 374 <interrupt_exit_kernel_prepare+0x2c> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> Reviewed-by: Nicholas Piggin <npiggin@gmail.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/1e883e9d93fdb256853d1434c8ad77c257349b2d.1615552866.git.christophe.leroy@csgroup.eu 
unrecoverable_exception() is never expected to return, most callers
have an infiniteloop in case it returns.

Ensure it really never returns by terminating it with a BUG(), and
declare it __no_return.

It always GCC to really simplify functions calling it. In the exemple
below, it avoids the stack frame in the likely fast path and avoids
code duplication for the exit.

With this patch:

	00000348 <interrupt_exit_kernel_prepare>:
	 348:	81 43 00 84 	lwz     r10,132(r3)
	 34c:	71 48 00 02 	andi.   r8,r10,2
	 350:	41 82 00 2c 	beq     37c <interrupt_exit_kernel_prepare+0x34>
	 354:	71 4a 40 00 	andi.   r10,r10,16384
	 358:	40 82 00 20 	bne     378 <interrupt_exit_kernel_prepare+0x30>
	 35c:	80 62 00 70 	lwz     r3,112(r2)
	 360:	74 63 00 01 	andis.  r3,r3,1
	 364:	40 82 00 28 	bne     38c <interrupt_exit_kernel_prepare+0x44>
	 368:	7d 40 00 a6 	mfmsr   r10
	 36c:	7c 11 13 a6 	mtspr   81,r0
	 370:	7c 12 13 a6 	mtspr   82,r0
	 374:	4e 80 00 20 	blr
	 378:	48 00 00 00 	b       378 <interrupt_exit_kernel_prepare+0x30>
	 37c:	94 21 ff f0 	stwu    r1,-16(r1)
	 380:	7c 08 02 a6 	mflr    r0
	 384:	90 01 00 14 	stw     r0,20(r1)
	 388:	48 00 00 01 	bl      388 <interrupt_exit_kernel_prepare+0x40>
				388: R_PPC_REL24	unrecoverable_exception
	 38c:	38 e2 00 70 	addi    r7,r2,112
	 390:	3d 00 00 01 	lis     r8,1
	 394:	7c c0 38 28 	lwarx   r6,0,r7
	 398:	7c c6 40 78 	andc    r6,r6,r8
	 39c:	7c c0 39 2d 	stwcx.  r6,0,r7
	 3a0:	40 a2 ff f4 	bne     394 <interrupt_exit_kernel_prepare+0x4c>
	 3a4:	38 60 00 01 	li      r3,1
	 3a8:	4b ff ff c0 	b       368 <interrupt_exit_kernel_prepare+0x20>

Without this patch:

	00000348 <interrupt_exit_kernel_prepare>:
	 348:	94 21 ff f0 	stwu    r1,-16(r1)
	 34c:	93 e1 00 0c 	stw     r31,12(r1)
	 350:	7c 7f 1b 78 	mr      r31,r3
	 354:	81 23 00 84 	lwz     r9,132(r3)
	 358:	71 2a 00 02 	andi.   r10,r9,2
	 35c:	41 82 00 34 	beq     390 <interrupt_exit_kernel_prepare+0x48>
	 360:	71 29 40 00 	andi.   r9,r9,16384
	 364:	40 82 00 28 	bne     38c <interrupt_exit_kernel_prepare+0x44>
	 368:	80 62 00 70 	lwz     r3,112(r2)
	 36c:	74 63 00 01 	andis.  r3,r3,1
	 370:	40 82 00 3c 	bne     3ac <interrupt_exit_kernel_prepare+0x64>
	 374:	7d 20 00 a6 	mfmsr   r9
	 378:	7c 11 13 a6 	mtspr   81,r0
	 37c:	7c 12 13 a6 	mtspr   82,r0
	 380:	83 e1 00 0c 	lwz     r31,12(r1)
	 384:	38 21 00 10 	addi    r1,r1,16
	 388:	4e 80 00 20 	blr
	 38c:	48 00 00 00 	b       38c <interrupt_exit_kernel_prepare+0x44>
	 390:	7c 08 02 a6 	mflr    r0
	 394:	90 01 00 14 	stw     r0,20(r1)
	 398:	48 00 00 01 	bl      398 <interrupt_exit_kernel_prepare+0x50>
				398: R_PPC_REL24	unrecoverable_exception
	 39c:	80 01 00 14 	lwz     r0,20(r1)
	 3a0:	81 3f 00 84 	lwz     r9,132(r31)
	 3a4:	7c 08 03 a6 	mtlr    r0
	 3a8:	4b ff ff b8 	b       360 <interrupt_exit_kernel_prepare+0x18>
	 3ac:	39 02 00 70 	addi    r8,r2,112
	 3b0:	3d 40 00 01 	lis     r10,1
	 3b4:	7c e0 40 28 	lwarx   r7,0,r8
	 3b8:	7c e7 50 78 	andc    r7,r7,r10
	 3bc:	7c e0 41 2d 	stwcx.  r7,0,r8
	 3c0:	40 a2 ff f4 	bne     3b4 <interrupt_exit_kernel_prepare+0x6c>
	 3c4:	38 60 00 01 	li      r3,1
	 3c8:	4b ff ff ac 	b       374 <interrupt_exit_kernel_prepare+0x2c>

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/1e883e9d93fdb256853d1434c8ad77c257349b2d.1615552866.git.christophe.leroy@csgroup.eu