Michael Neuling [off-list ref] writes:

On Wed, 2017-05-24 at 14:26 +0530, Aneesh Kumar K.V wrote:

quoted

Michael Neuling [off-list ref] writes:
=20

quoted

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 <redacted>
---
=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 },

quoted

quoted

=C2=A0	{ .pabyte =3D 0,=C2=A0=C2=A0.pabit =3D 6, .cpu_features=C2=A0=

=C2=A0=3D CPU_FTR_NOEXECUTE },

quoted

quoted

=C2=A0	{ .pabyte =3D 1,=C2=A0=C2=A0.pabit =3D 2, .mmu_features=C2=A0=

=C2=A0=3D MMU_FTR_CI_LARGE_PAGE

quoted

quoted

},
+#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 },

quoted

quoted

+#endif
=C2=A0	{ .pabyte =3D 1,=C2=A0=C2=A0.pabit =3D 1, .invert =3D 1, .cpu_f=

eatures =3D

quoted

quoted

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,

quoted

quoted

=C2=A0				=C2=A0=C2=A0=C2=A0=C2=A0.cpu_user_ftrs =3D PPC_FEATURE_TRUE_=

LE },

quoted

quoted

--=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.

quoted

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))

quoted

+	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