linux-kernel - [tip: x86/fpu] x86/process: Clone FPU in copy

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Date:   Wed, 20 Oct 2021 13:44:42 -0000
From:   "tip-bot2 for Thomas Gleixner" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Thomas Gleixner <tglx@...utronix.de>, Borislav Petkov <bp@...e.de>,
        x86@...nel.org, linux-kernel@...r.kernel.org
Subject: [tip: x86/fpu] x86/process: Clone FPU in copy_thread()

The following commit has been merged into the x86/fpu branch of tip:

Commit-ID:     2d16a1876f20218f8970ea4b7f679cead1cdb510
Gitweb:        https://git.kernel.org/tip/2d16a1876f20218f8970ea4b7f679cead1cdb510
Author:        Thomas Gleixner <tglx@...utronix.de>
AuthorDate:    Fri, 15 Oct 2021 03:16:04 +02:00
Committer:     Borislav Petkov <bp@...e.de>
CommitterDate: Wed, 20 Oct 2021 15:27:26 +02:00

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>
Signed-off-by: Borislav Petkov <bp@...e.de>
Link: https://lkml.kernel.org/r/20211015011538.780714235@linutronix.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 1d9463e..d2227c5 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();