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powerpc/64s: Avoid cpabort in context switch when possible

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The ISA v3.0B copy-paste facility only requires cpabort when switching
to a process that has foreign real addresses mapped (direct access to
accelerators), to clear a potential copy buffer filled by a previous
thread. There is no accelerator driver implemented yet, so cpabort can
be removed. It can be be re-added when a driver is implemented.

POWER9 DD1 requires the copy buffer to always be cleared on context
switch, but if accelerators are not in use, then an unpaired copy from
a dummy region is sufficient to clear data out of the copy buffer.

This increases context switch performance by about 5% on POWER9.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Nicholas Piggin
2017-06-09 01:36:09 +10:00
committed by Michael Ellerman
parent 9145effd62
commit 07d2a628bc
3 changed files with 30 additions and 14 deletions
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8
arch/powerpc/include/asm/ppc-opcode.h
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@@ -189,8 +189,7 @@
/* sorted alphabetically */
#define PPC_INST_BHRBE 0x7c00025c
#define PPC_INST_CLRBHRB 0x7c00035c
#define PPC_INST_COPY 0x7c00060c
#define PPC_INST_COPY_FIRST 0x7c20060c
#define PPC_INST_COPY 0x7c20060c
#define PPC_INST_CP_ABORT 0x7c00068c
#define PPC_INST_DCBA 0x7c0005ec
#define PPC_INST_DCBA_MASK 0xfc0007fe
@@ -223,8 +222,7 @@
#define PPC_INST_MSGSNDP 0x7c00011c
#define PPC_INST_MTTMR 0x7c0003dc
#define PPC_INST_NOP 0x60000000
#define PPC_INST_PASTE 0x7c00070c
#define PPC_INST_PASTE_LAST 0x7c20070d
#define PPC_INST_PASTE 0x7c20070d
#define PPC_INST_POPCNTB 0x7c0000f4
#define PPC_INST_POPCNTB_MASK 0xfc0007fe
#define PPC_INST_POPCNTD 0x7c0003f4
@@ -392,6 +390,8 @@
/* Deal with instructions that older assemblers aren't aware of */
#define PPC_CP_ABORT stringify_in_c(.long PPC_INST_CP_ABORT)
#define PPC_COPY(a, b) stringify_in_c(.long PPC_INST_COPY | \
___PPC_RA(a) | ___PPC_RB(b))
#define PPC_DCBAL(a, b) stringify_in_c(.long PPC_INST_DCBAL | \
__PPC_RA(a) | __PPC_RB(b))
#define PPC_DCBZL(a, b) stringify_in_c(.long PPC_INST_DCBZL | \