From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sebastian Andrzej Siewior Subject: [PATCH 03/22] x86/fpu: Remove preempt_disable() in fpu__clear() Date: Thu, 21 Feb 2019 12:50:01 +0100 Message-ID: <20190221115020.12385-4-bigeasy@linutronix.de> References: <20190221115020.12385-1-bigeasy@linutronix.de> Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Cc: x86@kernel.org, Andy Lutomirski , Paolo Bonzini , =?UTF-8?q?Radim=20Kr=C4=8Dm=C3=A1=C5=99?= , kvm@vger.kernel.org, "Jason A. Donenfeld" , Rik van Riel , Dave Hansen , Sebastian Andrzej Siewior , Borislav Petkov To: linux-kernel@vger.kernel.org Return-path: In-Reply-To: <20190221115020.12385-1-bigeasy@linutronix.de> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org The preempt_disable() section was introduced in commit a10b6a16cdad8 ("x86/fpu: Make the fpu state change in fpu__clear() scheduler-atomic") and it was said to be temporary. fpu__initialize() initializes the FPU struct to its "init" value and then sets ->initialized to 1. The last part is the important one. The content of the `state' does not matter because it gets set via copy_init_fpstate_to_fpregs(). A preemption here has little meaning because the registers will always be set to the same content after copy_init_fpstate_to_fpregs(). A softirq with a kernel_fpu_begin() could also force to save FPU's registers after fpu__initialize() without changing the outcome here. Remove the preempt_disable() section in fpu__clear(), preemption here does not hurt. Signed-off-by: Sebastian Andrzej Siewior Reviewed-by: Borislav Petkov --- arch/x86/kernel/fpu/core.c | 2 -- 1 file changed, 2 deletions(-) diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c index 1d3ae7988f7f2..1940319268aef 100644 --- a/arch/x86/kernel/fpu/core.c +++ b/arch/x86/kernel/fpu/core.c @@ -366,11 +366,9 @@ void fpu__clear(struct fpu *fpu) * Make sure fpstate is cleared and initialized. */ if (static_cpu_has(X86_FEATURE_FPU)) { - preempt_disable(); fpu__initialize(fpu); user_fpu_begin(); copy_init_fpstate_to_fpregs(); - preempt_enable(); } } -- 2.20.1