[PATCH 1/2] [PowerPC] Add simd.h implementation

[Shawn Landden]

On Tue, May 14, 2019 at 12:43 AM Benjamin Herrenschmidt
<benh at kernel.crashing.org> wrote:
>
> On Mon, 2019-05-13 at 22:44 -0300, Shawn Landden wrote:
> > +
> > +/*
> > + * Were we in user mode when we were
> > + * interrupted?
> > + *
> > + * Doing kernel_altivec/vsx_begin/end() is ok if we are running
> > + * in an interrupt context from user mode - we'll just
> > + * save the FPU state as required.
> > + */
> > +static bool interrupted_user_mode(void)
> > +{
> > +       struct pt_regs *regs = get_irq_regs();
> > +
> > +       return regs && user_mode(regs);
> > +}
> > +
>
> That's interesting .... it *could* work but we'll have to careful audit
> the code to make sure thats ok.
>
> We probably also want to handle the case where the CPU is in the idle
> loop.
That is the next patch. It is best to split these up because then git
bisect works better, and these are higher-risk changes.
>
> Do we always save the user state when switching out these days ? If
> yes, then there's no "live" state to worry about...
>
> Cheers,
> Ben.
>
>