linux-kernel - Re: [PATCH] powerpc: Make virt_to

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Message-ID: <CACRpkdayi5PyH7bifvShWRgtZXsNh9o8vA1TGV8tTORngeO8Hw@mail.gmail.com>
Date:   Mon, 14 Aug 2023 20:22:28 +0200
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Michael Ellerman <mpe@...erman.id.au>
Cc:     Nicholas Piggin <npiggin@...il.com>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org
Subject: Re: [PATCH] powerpc: Make virt_to_pfn() a static inline

On Mon, Aug 14, 2023 at 2:37 PM Michael Ellerman <mpe@...erman.id.au> wrote:

> > +static inline const void *pfn_to_kaddr(unsigned long pfn)
> > +{
> > +     return (const void *)(((unsigned long)__va(pfn)) << PAGE_SHIFT);
>
> Any reason to do it this way rather than:
>
> +       return __va(pfn << PAGE_SHIFT);
>
> Seems to be equivalent and much cleaner?

I was afraid of changing the semantic in the original macro
which converts to a virtual address before shifting, instead
of shifting first, but you're right, I'm too cautious. I'll propose
the elegant solution from you & Christophe instead!

Yours,
Linus Walleij