powerpc/32s: Save content of sr0 to avoid 'mfsr'

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Calling 'mfsr' to get the content of segment registers is heavy,
in addition it requires clearing of the 'reserved' bits.

In order to avoid this operation, save it in mm context and in
thread struct.

The saved sr0 is the one used by kernel, this means that on
locking entry it can be used as is.

For unlocking, the only thing to do is to clear SR_NX.

This improves null_syscall selftest by 12 cycles, ie 4%.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/b02baf2ed8f09bad910dfaeeb7353b2ae6830525.1634627931.git.christophe.leroy@csgroup.eu

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This commit is contained in:

Christophe Leroy 2021-10-19 09:29:18 +02:00 • committed by Michael Ellerman

parent 526d4a4c77

commit 70428da94c

8 changed files with 33 additions and 14 deletions

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5

arch/powerpc/include/asm/book3s/32/mmu-hash.h

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arch/powerpc/include/asm/processor.h

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arch/powerpc/kernel/asm-offsets.c

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arch/powerpc/kernel/entry_32.S

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arch/powerpc/mm/book3s32/kuap.c

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arch/powerpc/mm/book3s32/kuep.c

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arch/powerpc/mm/book3s32/mmu_context.c

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arch/powerpc/mm/mmu_context.c

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