linux-kernel - [patch V2 07/30] x86/process: Clone FPU in copy

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Message-ID: <20211015011538.780714235@linutronix.de>
Date:   Fri, 15 Oct 2021 03:16:04 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     x86@...nel.org, "Chang S. Bae" <chang.seok.bae@...el.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Arjan van de Ven <arjan@...ux.intel.com>,
        kvm@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>,
        "Liu, Jing2" <jing2.liu@...el.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Xiaoyao Li <xiaoyao.li@...el.com>
Subject: [patch V2 07/30] x86/process: Clone FPU in copy_thread()

There is no reason to clone FPU in arch_dup_task_struct(). Quite the
contrary it prevents optimizations. Move it to copy_thread()

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>

---
 arch/x86/kernel/process.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)
---
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 1d9463e3096b..d2227c55e683 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -87,7 +87,7 @@ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
 #ifdef CONFIG_VM86
 	dst->thread.vm86 = NULL;
 #endif
-	return fpu_clone(dst);
+	return 0;
 }
 
 /*
@@ -154,6 +154,8 @@ int copy_thread(unsigned long clone_flags, unsigned long sp, unsigned long arg,
 	frame->flags = X86_EFLAGS_FIXED;
 #endif
 
+	fpu_clone(p);
+
 	/* Kernel thread ? */
 	if (unlikely(p->flags & PF_KTHREAD)) {
 		p->thread.pkru = pkru_get_init_value();