Commit c06f0aff authored by Christophe Leroy's avatar Christophe Leroy Committed by Michael Ellerman
Browse files

powerpc: Don't use thread struct for saving SRR0/1 on syscall. 



CR0 can be saved later, and CTR can also be used for saving.

Keep SRR1 in r9 and stash SRR0 in CTR, this avoids using thread_struct
in memory for that.

Saves 3 cycles (ie 1%) in null_syscall selftest on 8xx.

Signed-off-by: default avatarChristophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/b94c3bc03bac9431fec2dadb686384c481889422.1580470483.git.christophe.leroy@c-s.fr
parent 9e270862

arch/powerpc/kernel/head_32.h

+7 −9
Original line number Diff line number Diff line
@@ -114,28 +114,23 @@ 
	mfspr	r9, SPRN_SRR1

#ifdef CONFIG_VMAP_STACK

	mfspr	r11, SPRN_SRR0

	stw	r11, SRR0(r12)

	stw	r9, SRR1(r12)

	mtctr	r11

#endif

	mfcr	r10

	andi.	r11, r9, MSR_PR

	lwz	r11,TASK_STACK-THREAD(r12)

	beq-	99f

	rlwinm	r10,r10,0,4,2	/* Clear SO bit in CR */

	addi	r11, r11, THREAD_SIZE - INT_FRAME_SIZE

#ifdef CONFIG_VMAP_STACK

	li	r9, MSR_KERNEL & ~(MSR_IR | MSR_RI) /* can take DTLB miss */

	mtmsr	r9

	li	r10, MSR_KERNEL & ~(MSR_IR | MSR_RI) /* can take DTLB miss */

	mtmsr	r10

	isync

#endif

	tovirt_vmstack r12, r12

	tophys_novmstack r11, r11

	stw	r10,_CCR(r11)		/* save registers */

	mflr	r10

	stw	r10, _LINK(r11)

#ifdef CONFIG_VMAP_STACK

	lwz	r10, SRR0(r12)

	lwz	r9, SRR1(r12)

	mfctr	r10

#else

	mfspr	r10,SPRN_SRR0

#endif
@@ -143,6 +138,9 @@ 
	stw	r1,0(r11)

	tovirt_novmstack r1, r11	/* set new kernel sp */

	stw	r10,_NIP(r11)

	mfcr	r10

	rlwinm	r10,r10,0,4,2	/* Clear SO bit in CR */

	stw	r10,_CCR(r11)		/* save registers */

#ifdef CONFIG_40x

	rlwinm	r9,r9,0,14,12		/* clear MSR_WE (necessary?) */

#else

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