Messages in this thread | | | Date | Tue, 5 Apr 2016 09:51:55 -0400 | Subject | Re: [PATCH 1/6] x86/fpu/regset: Use boot_cpu_has() | From | Brian Gerst <> |
| |
On Tue, Apr 5, 2016 at 2:29 AM, Borislav Petkov <bp@alien8.de> wrote: > From: Borislav Petkov <bp@suse.de> > > fpregs_{g,s}et() are not sizzling-hot paths to justify the need for > static_cpu_has(). Use the normal boot_cpu_has() helper. > > Signed-off-by: Borislav Petkov <bp@suse.de> > --- > arch/x86/kernel/fpu/regset.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/arch/x86/kernel/fpu/regset.c b/arch/x86/kernel/fpu/regset.c > index bc5e76c1d7c5..81422dfb152b 100644 > --- a/arch/x86/kernel/fpu/regset.c > +++ b/arch/x86/kernel/fpu/regset.c > @@ -278,7 +278,7 @@ int fpregs_get(struct task_struct *target, const struct user_regset *regset, > > fpu__activate_fpstate_read(fpu); > > - if (!static_cpu_has(X86_FEATURE_FPU)) > + if (!boot_cpu_has(X86_FEATURE_FPU)) > return fpregs_soft_get(target, regset, pos, count, kbuf, ubuf); > > if (!boot_cpu_has(X86_FEATURE_FXSR)) > @@ -309,7 +309,7 @@ int fpregs_set(struct task_struct *target, const struct user_regset *regset, > fpu__activate_fpstate_write(fpu); > fpstate_sanitize_xstate(fpu); > > - if (!static_cpu_has(X86_FEATURE_FPU)) > + if (!boot_cpu_has(X86_FEATURE_FPU)) > return fpregs_soft_set(target, regset, pos, count, kbuf, ubuf); > > if (!boot_cpu_has(X86_FEATURE_FXSR))
I think the general rule should be always use static_cpu_has() for runtime checks, since it reduces down to a single jmp/nop instruction after alternatives run. Even if it's not a hot path, it saves a bit of runtime memory. boot_cpu_has() is fine for run-once init code.
-- Brian Gerst
| |