diff options
| author | Nicholas Piggin | 2017-06-09 01:36:09 +1000 |
|---|---|---|
| committer | Michael Ellerman | 2017-06-15 16:34:39 +1000 |
| commit | 07d2a628bc0008f90754ac7982289f6cb0f46cf8 (patch) | |
| tree | fa8554770bf35735a791fd798a2dc3bd8ab45807 /arch/powerpc/kernel/entry_64.S | |
| parent | 9145effd626d155484f73db24ab3e142ecda31db (diff) | |
powerpc/64s: Avoid cpabort in context switch when possible
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>
Diffstat (limited to 'arch/powerpc/kernel/entry_64.S')
| -rw-r--r-- | arch/powerpc/kernel/entry_64.S | 9 |
1 files changed, 0 insertions, 9 deletions
diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S index fb143859cc68..da9486e2fd89 100644 --- a/arch/powerpc/kernel/entry_64.S +++ b/arch/powerpc/kernel/entry_64.S @@ -536,15 +536,6 @@ _GLOBAL(_switch) * which contains larx/stcx, which will clear any reservation * of the task being switched. */ - -BEGIN_FTR_SECTION -/* - * A cp_abort (copy paste abort) here ensures that when context switching, a - * copy from one process can't leak into the paste of another. - */ - PPC_CP_ABORT -END_FTR_SECTION_IFSET(CPU_FTR_ARCH_300) - #ifdef CONFIG_PPC_BOOK3S /* Cancel all explict user streams as they will have no use after context * switch and will stop the HW from creating streams itself |