[tip:x86/fpu] x86/fpu: Remove fpu__restore()

tip-bot for Sebastian Andrzej Siewior
2019-04-13T20:47:56Z

Commit-ID: 6dd677a044e606fd343e31c2108b13d74aec1ca5
Gitweb: https://git.kernel.org/tip/6dd677a044e606fd343e31c2108b13d74aec1ca5
Author: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
AuthorDate: Wed, 3 Apr 2019 18:41:31 +0200
Committer: Borislav Petkov <bp@suse.de>
CommitDate: Tue, 9 Apr 2019 19:27:42 +0200

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

b3b0870ef3ffe ("i387: do not preload FPU state at task switch time")

and has no meaning since.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Dave Hansen <dave.hansen@intel.com>
Reviewed-by: Thomas 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
---
Documentation/preempt-locking.txt | 1 -
arch/x86/include/asm/fpu/internal.h | 1 -
arch/x86/kernel/fpu/core.c | 24 ------------------------
arch/x86/kernel/process_32.c | 4 +---
arch/x86/kernel/process_64.c | 4 +---
5 files changed, 2 insertions(+), 32 deletions(-)

diff --git a/Documentation/preempt-locking.txt b/Documentation/preempt-locking.txt
index 509f5a422d57..dce336134e54 100644
--- a/Documentation/preempt-locking.txt
+++ b/Documentation/preempt-locking.txt
@@ -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
diff --git a/arch/x86/include/asm/fpu/internal.h b/arch/x86/include/asm/fpu/internal.h
index fb04a3ded7dd..75a1d5f712ee 100644
--- a/arch/x86/include/asm/fpu/internal.h
+++ b/arch/x86/include/asm/fpu/internal.h
@@ -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);
diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
index 2e5003fef51a..1d3ae7988f7f 100644
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -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
diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c
index e471d8e6f0b2..7888a41a03cd 100644
--- a/arch/x86/kernel/process_32.c
+++ b/arch/x86/kernel/process_32.c
@@ -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);

diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index 6a62f4af9fcf..e1983b3a16c4 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -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);