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

[Venkat Rao Bagalkote <venkat88@linux.ibm.com>]

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@linux.ibm.com>
>>>> ---
>>>>   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
>>>>
>>>>
>
>