Re: [PATCH v3 2/3] arch/arm64: fpsimd: Introduce fpsimd_save_and_flush_cpu_state() and use it

[Julien Grall]

Hi Dave,

On 24/04/2019 14:17, Dave Martin wrote:
> On Tue, Apr 23, 2019 at 02:57:18PM +0100, Julien Grall wrote:
> > tent-Length: 4295
> > Lines: 128
> >
> > The only external user of fpsimd_save() and fpsimd_flush_cpu_state() is
> > the KVM FPSIMD code.
> >
> > A following patch will introduce a mechanism to acquire owernship of the
> > FPSIMD/SVE context for performing context management operations. Rather
> > than having to export the new helpers to get/put the context, we can just
> > introduce a new function to combine fpsimd_save() and
> > fpsimd_flush_cpu_state().
> >
> > This has also the advantage to remove any external call of fpsimd_save()
> > and fpsimd_flush_cpu_state(), so they can be turned static.
> >
> > Lastly, the new function can also be used in the PM notifier.
> >
> > Signed-off-by: Julien Grall <julien.grall@xxxxxxx>
> >
> > ---
> >      kernel_neon_begin() does not use fpsimd_save_and_flush_cpu_state()
> >      because the next patch will modify the function to also grab the
> >      FPSIMD/SVE context.
> >
> >      Changes in v3:
> >          - Rework the commit message
> >          - Move the prototype of fpsimd_save_and_flush_cpu_state()
> >          further down in the header
> >          - Remove comment in kvm_arch_vcpu_put_fp()
> >
> >      Changes in v2:
> >          - Patch added
> > ---
> >   arch/arm64/include/asm/fpsimd.h |  5 ++---
> >   arch/arm64/kernel/fpsimd.c      | 17 +++++++++++++----
> >   arch/arm64/kvm/fpsimd.c         |  4 +---
> >   3 files changed, 16 insertions(+), 10 deletions(-)
> >
> > diff --git a/arch/arm64/include/asm/fpsimd.h b/arch/arm64/include/asm/fpsimd.h
> > index b73d12fcc7f9..c311d36ecffe 100644
> > --- a/arch/arm64/include/asm/fpsimd.h
> > +++ b/arch/arm64/include/asm/fpsimd.h
> > @@ -48,8 +48,6 @@ struct task_struct;
> >   extern void fpsimd_save_state(struct user_fpsimd_state *state);
> >   extern void fpsimd_load_state(struct user_fpsimd_state *state);
> >   
> > -extern void fpsimd_save(void);
> > -
> >   extern void fpsimd_thread_switch(struct task_struct *next);
> >   extern void fpsimd_flush_thread(void);
> >   
> > @@ -63,7 +61,8 @@ extern void fpsimd_bind_state_to_cpu(struct user_fpsimd_state *state,
> >   				     void *sve_state, unsigned int sve_vl);
> >   
> >   extern void fpsimd_flush_task_state(struct task_struct *target);
> > -extern void fpsimd_flush_cpu_state(void);
> > +
> > +extern void fpsimd_save_and_flush_cpu_state(void);
>
> Nit: You could drop this blank line: these are all "state maintenance"
> operations, roughly speaking.
>
> But don't bother unless you respin for some other reason.

It looks like I will need to make some changes in patch #3. So I will remove the 
line at the same time.

> [...]
>
> With or without that,
>
> Reviewed-by: Dave Martin <Dave.Martin@xxxxxxx>

Thank you!

Cheers,

--
Julien Grall