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x86/fpu: Don't export __kernel_fpu_{begin,end}()

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[ Upstream commit 12209993e9 ]

There is one user of __kernel_fpu_begin() and before invoking it,
it invokes preempt_disable(). So it could invoke kernel_fpu_begin()
right away. The 32bit version of arch_efi_call_virt_setup() and
arch_efi_call_virt_teardown() does this already.

The comment above *kernel_fpu*() claims that before invoking
__kernel_fpu_begin() preemption should be disabled and that KVM is a
good example of doing it. Well, KVM doesn't do that since commit

  f775b13eed ("x86,kvm: move qemu/guest FPU switching out to vcpu_run")

so it is not an example anymore.

With EFI gone as the last user of __kernel_fpu_{begin|end}(), both can
be made static and not exported anymore.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Rik van Riel <riel@surriel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Nicolai Stange <nstange@suse.de>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: kvm ML <kvm@vger.kernel.org>
Cc: linux-efi <linux-efi@vger.kernel.org>
Cc: x86-ml <x86@kernel.org>
Link: https://lkml.kernel.org/r/20181129150210.2k4mawt37ow6c2vq@linutronix.de
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
This commit is contained in:
Sebastian Andrzej Siewior 2018-11-29 16:02:10 +01:00 committed by Greg Kroah-Hartman
parent c54a881d79
commit a725c5201f
3 changed files with 9 additions and 18 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

6
arch/x86/include/asm/efi.h
View file

@ -82,8 +82,7 @@ struct efi_scratch {
#define arch_efi_call_virt_setup() \
({ \
efi_sync_low_kernel_mappings(); \
preempt_disable(); \
__kernel_fpu_begin(); \
kernel_fpu_begin(); \
firmware_restrict_branch_speculation_start(); \
\
if (efi_scratch.use_pgd) { \
@ -104,8 +103,7 @@ struct efi_scratch {
} \
\
firmware_restrict_branch_speculation_end(); \
__kernel_fpu_end(); \
preempt_enable(); \
kernel_fpu_end(); \
})
extern void __iomem *__init efi_ioremap(unsigned long addr, unsigned long size,

15
arch/x86/include/asm/fpu/api.h
View file

@ -12,17 +12,12 @@
#define _ASM_X86_FPU_API_H
/*
* Careful: __kernel_fpu_begin/end() must be called with preempt disabled
* and they don't touch the preempt state on their own.
* If you enable preemption after __kernel_fpu_begin(), preempt notifier
* should call the __kernel_fpu_end() to prevent the kernel/user FPU
* state from getting corrupted. KVM for example uses this model.
*
* All other cases use kernel_fpu_begin/end() which disable preemption
* during kernel FPU usage.
* Use kernel_fpu_begin/end() if you intend to use FPU in kernel context. It
* disables preemption so be careful if you intend to use it for long periods
* of time.
* If you intend to use the FPU in softirq you need to check first with
* irq_fpu_usable() if it is possible.
*/
extern void __kernel_fpu_begin(void);
extern void __kernel_fpu_end(void);
extern void kernel_fpu_begin(void);
extern void kernel_fpu_end(void);
extern bool irq_fpu_usable(void);

6
arch/x86/kernel/fpu/core.c
View file

@ -93,7 +93,7 @@ bool irq_fpu_usable(void)
}
EXPORT_SYMBOL(irq_fpu_usable);
void __kernel_fpu_begin(void)
static void __kernel_fpu_begin(void)
{
struct fpu *fpu = &current->thread.fpu;
@ -111,9 +111,8 @@ void __kernel_fpu_begin(void)
__cpu_invalidate_fpregs_state();
}
}
EXPORT_SYMBOL(__kernel_fpu_begin);
void __kernel_fpu_end(void)
static void __kernel_fpu_end(void)
{
struct fpu *fpu = &current->thread.fpu;
@ -122,7 +121,6 @@ void __kernel_fpu_end(void)
kernel_fpu_enable();
}
EXPORT_SYMBOL(__kernel_fpu_end);
void kernel_fpu_begin(void)
{