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Subject: Re: [PATCH v2 1/6] powerpc/code-patching: Implement generic text
 patching function
From: Benjamin Gray <bgray@linux.ibm.com>
To: Christophe Leroy <christophe.leroy@csgroup.eu>,
        "linuxppc-dev@lists.ozlabs.org"
	 <linuxppc-dev@lists.ozlabs.org>
Date: Wed, 28 Sep 2022 11:30:02 +1000
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On Tue, 2022-09-27 at 06:40 +0000, Christophe Leroy wrote:
> > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0/* Flush on the EA that may =
be executed in case of a non-
> > coherent icache */
> > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0icbi(prog_addr);
>=20
> prog_addr is a misleading name ? Is that the address at which you=20
> program it ? Is that the address the programs runs at ?
>=20
> exec_addr was a lot more explicit as it clearly defines the address
> at=20
> which the code is executed.

I'm not sure what it could be confused for other than "the address the
program uses" (be it uses for executing, or uses as data).=C2=A0I just
called it that because it's not necessarily executed, so 'exec_addr' is
misleading (to the extent it matters in the first place...).

> > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0if (IS_ENABLED(CONFIG_PPC64)=
 && L1_CACHE_BYTES < 64)
> > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0icbi(prog_addr + size - 1);
>=20
> This doesn't exist today.
>=20
> I'd rather have:
>=20
> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0BUILD_BUG_ON(IS_ENABLED(C=
ONFIG_PPC64) && L1_CACHE_BYTES <
> 64);

Sure, I can adjust the style.

> > +static int __always_inline __do_patch_memory(void *dest, unsigned
> > long src, size_t size)
> > =C2=A0 {
> > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0int err;
> > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0u32 *patch_addr;
> > -=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0unsigned long text_poke_addr=
;
> > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0pte_t *pte;
> > -=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0unsigned long pfn =3D get_pa=
tch_pfn(addr);
> > -
> > -=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0text_poke_addr =3D (unsigned
> > long)__this_cpu_read(text_poke_area)->addr & PAGE_MASK;
> > -=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0patch_addr =3D (u32 *)(text_=
poke_addr +
> > offset_in_page(addr));
> > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0unsigned long text_poke_addr=
 =3D (unsigned
> > long)__this_cpu_read(text_poke_area)->addr & PAGE_MASK;
> > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0unsigned long pfn =3D get_pa=
tch_pfn(dest);
> >=20
> > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0patch_addr =3D (u32 *)(text_=
poke_addr +
> > offset_in_page(dest));
>=20
> Can we avoid this churn ?
> Ok, you want to change 'addr' to 'dest', can we leave everything else
> as=20
> is ?

'addr' was only renamed because the v1 used a pointer to the data, so
'addr' was ambiguous. I'll restore it to 'addr' for v3.

I'll also restore the formatting.