From d45d7ff7047f7f6c3221b0f028fade640812f931 Mon Sep 17 00:00:00 2001 From: Mark Brown Date: Tue, 19 Apr 2022 12:22:30 +0100 Subject: arm64/sme: Disable streaming mode and ZA when flushing CPU state 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 Reviewed-by: Catalin Marinas Link: https://lore.kernel.org/r/20220419112247.711548-23-broonie@kernel.org Signed-off-by: Catalin Marinas --- arch/arm64/kernel/fpsimd.c | 9 +++++++++ 1 file changed, 9 insertions(+) (limited to 'arch/arm64/kernel/fpsimd.c') diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c index 94f06e9d37cf..9592cdd7d635 100644 --- a/arch/arm64/kernel/fpsimd.c +++ b/arch/arm64/kernel/fpsimd.c @@ -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); } -- cgit