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arm64/sme: Disable streaming mode and ZA when flushing CPU state

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Both streaming mode and ZA may increase power consumption when they are
enabled and streaming mode makes many FPSIMD and SVE instructions undefined
which will cause problems for any kernel mode floating point so disable
both when we flush the CPU state. This covers both kernel_neon_begin() and
idle and after flushing the state a reload is always required anyway.

Signed-off-by: Mark Brown <broonie@kernel.org>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/20220419112247.711548-23-broonie@kernel.org
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
This commit is contained in:
Mark Brown 2022-04-19 12:22:30 +01:00 committed by Catalin Marinas
parent 776b4a1cf3
commit d45d7ff704
1 changed files with 9 additions and 0 deletions
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9
arch/arm64/kernel/fpsimd.c
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@ -1759,6 +1759,15 @@ static void fpsimd_flush_cpu_state(void)
{
WARN_ON(!system_supports_fpsimd());
__this_cpu_write(fpsimd_last_state.st, NULL);
/*
* Leaving streaming mode enabled will cause issues for any kernel
* NEON and leaving streaming mode or ZA enabled may increase power
* consumption.
*/
if (system_supports_sme())
sme_smstop();
set_thread_flag(TIF_FOREIGN_FPSTATE);
}