From b2482807fbd48a299512d161e38262fd7d973aa0 Mon Sep 17 00:00:00 2001 From: Mark Brown Date: Tue, 10 Jan 2023 19:34:36 +0000 Subject: [PATCH] arm64/sme: Optimise SME exit on syscall entry Our ABI says that we exit streaming mode on syscall entry. Currently we check if we are in streaming mode before doing this but since we have a SMSTOP SM instruction which will clear SVCR.SM in a single atomic operation we can save ourselves the read of the system register and check of the flag and just unconditionally do the SMSTOP SM. If we are not in streaming mode it results in a noop change to SVCR, if we are in streaming mode we will exit as desired. No functional change. Signed-off-by: Mark Brown Link: https://lore.kernel.org/r/20230110-arm64-sme-syscall-smstop-v1-1-ac94235fd810@kernel.org Signed-off-by: Catalin Marinas --- arch/arm64/kernel/syscall.c | 8 ++------ 1 file changed, 2 insertions(+), 6 deletions(-) diff --git a/arch/arm64/kernel/syscall.c b/arch/arm64/kernel/syscall.c index a5de47e3df2ba..da84cf855c444 100644 --- a/arch/arm64/kernel/syscall.c +++ b/arch/arm64/kernel/syscall.c @@ -173,12 +173,8 @@ static inline void fp_user_discard(void) * register state to track, if this changes the KVM code will * need updating. */ - if (system_supports_sme() && test_thread_flag(TIF_SME)) { - u64 svcr = read_sysreg_s(SYS_SVCR); - - if (svcr & SVCR_SM_MASK) - sme_smstop_sm(); - } + if (system_supports_sme()) + sme_smstop_sm(); if (!system_supports_sve()) return; -- 2.30.2