Re: [PATCH] powerpc/interrupt: Use early_radix_enabled() in NMI real-mode guard

[Venkat Rao Bagalkote]

On 07/09/26 10:57 pm, Shrikanth Hegde wrote:
> On 9/7/26 2:24 PM, Venkat Rao Bagalkote wrote:
> > On 07/09/26 2:04 pm, Michal Suchánek wrote:
> > > Hello,
> > >
> > > On Mon, Sep 07, 2026 at 12:30:58PM +0530, Venkat Rao Bagalkote wrote:
> > > > radix_enabled() uses a jump label which is only valid after
> > > > mmu_feature_keys_init() is called. Before that point, on a pSeries
> > > > hash guest, early_check_vec5() clears MMU_FTR_TYPE_RADIX in
> > > > cur_cpu_spec->mmu_features but the jump label has not yet been 
> > > > patched,
> > > > so radix_enabled() incorrectly returns true.
> > > >
> > > > Replace radix_enabled() with early_radix_enabled() which does a plain
> > > > bitmask check against cur_cpu_spec->mmu_features and is correct at all
> > > > times, including before jump label initialization.
> > > Any Fixes: here?
> >
> >
> > Hello Michal,
> >
> > Yes, this can have.
> >
> > Fixes: 118178e62e2e ("powerpc: move NMI entry/exit code into wrapper")
> >
> > As commit  originally introduced !radxi_enabled() check in NMI 
> > wrapper path.
>
> looks like it did movement of code, rather than introducing.

Hello Shrikanth,

Yes, you are right. commit 118178e62e2e, just consolidated NMI wrapper 
logic from arch/powerpc/kernel/mce.c into interrupt.h.

Tracing it further back, radix_enabled() check for pseries hash guest in 
real-mode NMI was originally introduced in

commit: 8d0e21012743 ("powerpc/mce: Avoid nmi_enter/exit in real mode on 
pseries hash")

I can add Fixes: 8d0e21012743, and send V2, if that works.

Regards,

Venkat.

> > Regards,
> >
> > Venkat.
> >
> > > Thanks
> > >
> > > Michal
> > >
> > > > Add the missing #include <asm/mmu.h> since early_radix_enabled() is
> > > > declared there.
> > > >
> > > > Signed-off-by: Venkat Rao Bagalkote <venkat88@xxxxxxxxxxxxx>
> > > > ---
> > > >   arch/powerpc/include/asm/interrupt.h | 5 +++--
> > > >   1 file changed, 3 insertions(+), 2 deletions(-)
> > > >
> > > > diff --git a/arch/powerpc/include/asm/interrupt.h 
> > > > b/arch/powerpc/include/asm/interrupt.h
> > > > index 1b45a49e9bed..36a654e780f7 100644
> > > > --- a/arch/powerpc/include/asm/interrupt.h
> > > > +++ b/arch/powerpc/include/asm/interrupt.h
> > > > @@ -71,6 +71,7 @@
> > > >   #include <asm/kprobes.h>
> > > >   #include <asm/runlatch.h>
> > > > +#include <asm/mmu.h>
> > > >   #ifdef CONFIG_PPC_IRQ_SOFT_MASK_DEBUG
> > > >   /*
> > > > @@ -290,7 +291,7 @@ interrupt_handler long func(struct pt_regs 
> > > > *regs)            \
> > > >           state = irqentry_nmi_enter(regs);            \
> > > >       } else if (IS_ENABLED(CONFIG_PPC_BOOK3S_64) &&            \
> > > >              firmware_has_feature(FW_FEATURE_LPAR) &&        \
> > > > -           !radix_enabled()) {                    \
> > > > +           !early_radix_enabled()) {                \
> > > >           /* no nmi_entry for a pseries hash guest        \
> > > >            * taking a real mode exception */            \
> > > >       } else if (IS_ENABLED(CONFIG_KASAN)) { \
> > > > @@ -307,7 +308,7 @@ interrupt_handler long func(struct pt_regs 
> > > > *regs)            \
> > > >           irqentry_nmi_exit(regs, state);                \
> > > >       } else if (IS_ENABLED(CONFIG_PPC_BOOK3S_64) &&            \
> > > >              firmware_has_feature(FW_FEATURE_LPAR) &&        \
> > > > -           !radix_enabled()) {                    \
> > > > +           !early_radix_enabled()) {                \
> > > >           /* no nmi_exit for a pseries hash guest \
> > > >            * taking a real mode exception */            \
> > > >       } else if (IS_ENABLED(CONFIG_KASAN)) { \
> > > > --
> > > > 2.45.2