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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: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/b94c3bc03bac9431fec2dadb686384c481889422.1580470483.git.christophe.leroy@c-s.fr
This commit is contained in:
Christophe Leroy 2020-01-31 11:34:55 +00:00 committed by Michael Ellerman
parent 9e27086292
commit c06f0aff03
1 changed files with 7 additions and 9 deletions
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16
arch/powerpc/kernel/head_32.h
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@ -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