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

["Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>]

Michael Neuling <mikey@neuling.org> writes:

> 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 MM=
U_FTR_TYPE_RADIX },
>> > +#endif
>> > =C2=A0	{ .pabyte =3D 1,=C2=A0=C2=A0.pabit =3D 1, .invert =3D 1, .cpu_f=
eatures =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_=
LE },
>> > --=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_f=
eatures
> 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.
>

mpe/next at the time of this merge window. Do you want me to send a
complete patch against latest mpe/next ?

-aneesh