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Subject: Re: [PATCH v9 2/7] powerpc/code-patching: Handle RWX patching
 initialisation error
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: Thu, 03 Nov 2022 09:37:40 +1100
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On Wed, 2022-11-02 at 09:36 +0000, Christophe Leroy wrote:
> Le 25/10/2022 =C3=A0 06:44, Benjamin Gray a =C3=A9crit=C2=A0:
> > Detect and abort __do_patch_instruction() when there is no
> > text_poke_area,
> > which implies there is no patching address. This allows
> > patch_instruction()
> > to fail gracefully and let the caller decide what to do, as opposed
> > to
> > the current behaviour of kernel panicking when the null pointer is
> > dereferenced.
>=20
> Is there any reason at all to have no text_poke_area ?
>=20
> If that's the boot CPU, then it means we are really early in the boot
> process and will use raw_patch_instruction() directly. Or it means we
> don't have enough memory for the boot CPU, in which case you are
> going=20
> to have so many problems that it is not worth any effort.
>=20
> If it is not the boot CPU, isn't there a way to not add a CPU for
> which=20
> the allocation has failed ? If text_area_cpu_up() returns an error,=20
> isn't the CPU deactivated ?

Right, I hadn't seen that the CPU isn't onlined if the startup fails.
That would make the check redundant then.