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Commit 6dd677a0 authored by Sebastian Andrzej Siewior's avatar Sebastian Andrzej Siewior Committed by Borislav Petkov
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x86/fpu: Remove fpu__restore() 



There are no users of fpu__restore() so it is time to remove it. The
comment regarding fpu__restore() and TS bit is stale since commit

  b3b0870e ("i387: do not preload FPU state at task switch time")

and has no meaning since.

Signed-off-by: default avatarSebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
Reviewed-by: default avatarDave Hansen <dave.hansen@intel.com>
Reviewed-by: default avatarThomas Gleixner <tglx@linutronix.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Aubrey Li <aubrey.li@intel.com>
Cc: Babu Moger <Babu.Moger@amd.com>
Cc: "Chang S. Bae" <chang.seok.bae@intel.com>
Cc: Dmitry Safonov <dima@arista.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jann Horn <jannh@google.com>
Cc: "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc: Joerg Roedel <jroedel@suse.de>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: kvm ML <kvm@vger.kernel.org>
Cc: linux-doc@vger.kernel.org
Cc: Nicolai Stange <nstange@suse.de>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: x86-ml <x86@kernel.org>
Link: https://lkml.kernel.org/r/20190403164156.19645-3-bigeasy@linutronix.de
parent 39ea9baf

Documentation/preempt-locking.txt

+0 −1
Original line number Diff line number Diff line
@@ -52,7 +52,6 @@ preemption must be disabled around such regions. 


Note, some FPU functions are already explicitly preempt safe.  For example,

kernel_fpu_begin and kernel_fpu_end will disable and enable preemption.

However, fpu__restore() must be called with preemption disabled.





RULE #3: Lock acquire and release must be performed by same task

arch/x86/include/asm/fpu/internal.h

+0 −1
Original line number Diff line number Diff line
@@ -28,7 +28,6 @@ extern void fpu__initialize(struct fpu *fpu); 
extern void fpu__prepare_read(struct fpu *fpu);

extern void fpu__prepare_write(struct fpu *fpu);

extern void fpu__save(struct fpu *fpu);

extern void fpu__restore(struct fpu *fpu);

extern int  fpu__restore_sig(void __user *buf, int ia32_frame);

extern void fpu__drop(struct fpu *fpu);

extern int  fpu__copy(struct fpu *dst_fpu, struct fpu *src_fpu);

arch/x86/kernel/fpu/core.c

+0 −24
Original line number Diff line number Diff line
@@ -303,30 +303,6 @@ void fpu__prepare_write(struct fpu *fpu) 
	}

}



/*

 * 'fpu__restore()' is called to copy FPU registers from

 * the FPU fpstate to the live hw registers and to activate

 * access to the hardware registers, so that FPU instructions

 * can be used afterwards.

 *

 * Must be called with kernel preemption disabled (for example

 * with local interrupts disabled, as it is in the case of

 * do_device_not_available()).

 */

void fpu__restore(struct fpu *fpu)

{

	fpu__initialize(fpu);



	/* Avoid __kernel_fpu_begin() right after fpregs_activate() */

	kernel_fpu_disable();

	trace_x86_fpu_before_restore(fpu);

	fpregs_activate(fpu);

	copy_kernel_to_fpregs(&fpu->state);

	trace_x86_fpu_after_restore(fpu);

	kernel_fpu_enable();

}

EXPORT_SYMBOL_GPL(fpu__restore);



/*

 * Drops current FPU state: deactivates the fpregs and

 * the fpstate. NOTE: it still leaves previous contents

arch/x86/kernel/process_32.c

+1 −3
Original line number Diff line number Diff line
@@ -267,9 +267,7 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p) 
	/*

	 * Leave lazy mode, flushing any hypercalls made here.

	 * This must be done before restoring TLS segments so

	 * the GDT and LDT are properly updated, and must be

	 * done before fpu__restore(), so the TS bit is up

	 * to date.

	 * the GDT and LDT are properly updated.

	 */

	arch_end_context_switch(next_p);

arch/x86/kernel/process_64.c

+1 −3
Original line number Diff line number Diff line
@@ -538,9 +538,7 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p) 
	/*

	 * Leave lazy mode, flushing any hypercalls made here.  This

	 * must be done after loading TLS entries in the GDT but before

	 * loading segments that might reference them, and and it must

	 * be done before fpu__restore(), so the TS bit is up to

	 * date.

	 * loading segments that might reference them.

	 */

	arch_end_context_switch(next_p);