Re: [PATCH 1/2] kernel: add platform_has() infrastructure

[Juergen Gross]

On 26.04.22 19:31, Borislav Petkov wrote:
> On Tue, Apr 26, 2022 at 03:40:20PM +0200, Juergen Gross wrote:
> > diff --git a/kernel/platform-feature.c b/kernel/platform-feature.c
> > new file mode 100644
> > index 000000000000..2d52f8442cd5
> > --- /dev/null
> > +++ b/kernel/platform-feature.c
> > @@ -0,0 +1,7 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +
> > +#include <linux/cache.h>
> > +#include <linux/platform-feature.h>
> > +
> > +unsigned long __read_mostly platform_features[PLATFORM_FEAT_ARRAY_SZ];
>
> Probably __ro_after_init.

Yes, good idea.

> > +EXPORT_SYMBOL_GPL(platform_features);
>
> You probably should make that thing static and use only accessors to
> modify it in case you wanna change the underlying data structure in the
> future.

The question is whether we think that those platform features will be used
in hot paths or not. If so the inline accessors (at least the platform_has()
one) would be preferred IMO.

OTOH really performance critical cases could use static_branch or such.


Juergen

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