Re: [PATCH] powerpc: Fix booting P9 hash with CONFIG_PPC_RADIX_MMU=N

[Michael Neuling <mikey@neuling.org>]

On Wed, 2017-05-24 at 14:26 +0530, Aneesh Kumar K.V wrote:
> Michael Neuling <mikey@neuling.org> writes:
>=20
> > Currently if you disable CONFIG_PPC_RADIX_MMU you'll crash on boot on
> > a P9. This is because we still set MMU_FTR_TYPE_RADIX via
> > ibm,pa-features and MMU_FTR_TYPE_RADIX is what's used for code patching
> > in much of the asm code (ie. slb_miss_realmode)
> >=20
> > This patch fixes the problem by stopping MMU_FTR_TYPE_RADIX from being
> > set from ibm.pa-features.
> >=20
> > We may eventually end up removing the CONFIG_PPC_RADIX_MMU option
> > completely but until then this fixes the issue.
> >=20
> > Signed-off-by: Michael Neuling <mikey@neuling.org>
> > ---
> > =C2=A0arch/powerpc/kernel/prom.c | 2 ++
> > =C2=A01 file changed, 2 insertions(+)
> >=20
> > diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c
> > index 40c4887c27..f830562974 100644
> > --- a/arch/powerpc/kernel/prom.c
> > +++ b/arch/powerpc/kernel/prom.c
> > @@ -161,7 +161,9 @@ static struct ibm_pa_feature {
> > =C2=A0	{ .pabyte =3D 0,=C2=A0=C2=A0.pabit =3D 3, .cpu_features=C2=A0=C2=
=A0=3D CPU_FTR_CTRL },
> > =C2=A0	{ .pabyte =3D 0,=C2=A0=C2=A0.pabit =3D 6, .cpu_features=C2=A0=C2=
=A0=3D CPU_FTR_NOEXECUTE },
> > =C2=A0	{ .pabyte =3D 1,=C2=A0=C2=A0.pabit =3D 2, .mmu_features=C2=A0=C2=
=A0=3D MMU_FTR_CI_LARGE_PAGE
> > },
> > +#ifdef CONFIG_PPC_RADIX_MMU
> > =C2=A0	{ .pabyte =3D 40, .pabit =3D 0, .mmu_features=C2=A0=C2=A0=3D MMU=
_FTR_TYPE_RADIX },
> > +#endif
> > =C2=A0	{ .pabyte =3D 1,=C2=A0=C2=A0.pabit =3D 1, .invert =3D 1, .cpu_fe=
atures =3D
> > CPU_FTR_NODSISRALIGN },
> > =C2=A0	{ .pabyte =3D 5,=C2=A0=C2=A0.pabit =3D 0, .cpu_features=C2=A0=C2=
=A0=3D CPU_FTR_REAL_LE,
> > =C2=A0				=C2=A0=C2=A0=C2=A0=C2=A0.cpu_user_ftrs =3D PPC_FEATURE_TRUE_L=
E },
> > --=C2=A0
> > 2.11.0
>=20
> Instead can we do that feature removal in mmu_early_init_devtree. ie,
> something like

It looks like mmu_early_init_devtree() gets called after parsing ibm,pa_fea=
tures
so that should work.

> diff --git a/arch/powerpc/mm/init_64.c b/arch/powerpc/mm/init_64.c
> index 8f6f2a173e47..8f43f3827bac 100644
> --- a/arch/powerpc/mm/init_64.c
> +++ b/arch/powerpc/mm/init_64.c
> @@ -394,7 +394,7 @@ void __init mmu_early_init_devtree(v
> oid)
> =C2=A0{
> =C2=A0	/* Disable radix mode based on kernel command line. */
> =C2=A0	/* We don't yet have the machinery to do radix as a guest. */
> -	if (disable_radix || !(mfmsr() & MSR_HV))
> > +	if (!IS_ENABLED(CONFIG_PPC_RADIX_MMU) || disable_radix || !(mfmsr() &=
 MSR_HV))

What tree is this patch against?  Linus' tree doesn't look like that.

Mikey


> =C2=A0		cur_cpu_spec->mmu_features &=3D ~MMU_FTR_TYPE_RADIX;
> =C2=A0
> =C2=A0	/*
>=20