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UPSTREAM: 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>
(cherry picked from commit d45d7ff704)
Signed-off-by: Will Deacon <willdeacon@google.com>
Bug: 233587962
Bug: 233588291
Change-Id: Id0e7342d5ea9b7e5f58dadc605115a3c4f8beb10
This commit is contained in:
Mark Brown
2022-04-19 12:22:30 +01:00
committed by Will Deacon
parent 80c133094b
commit 4b54a99d42
1 changed files with 9 additions and 0 deletions
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9
arch/arm64/kernel/fpsimd.c
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@@ -1756,6 +1756,15 @@ 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);
}