Re: [PATCH] powerpc/970: fix nap return address corruption on async interrupt exit

On 7/29/26 2:27 PM, Thorsten Leemhuis wrote:

On 7/23/26 13:52, John Ogness wrote:

quoted

On 2026-07-16, John Ogness [off-list ref] wrote:

quoted

On 2026-07-07, "Mukesh Kumar Chaurasiya (IBM)" [off-list ref] wrote:

quoted

On PowerMac G5 (PPC970, CONFIG_PPC_970_NAP) the system panics shortly
after boot with symptoms including instruction fetch faults, kernel data
access faults, and stack corruption, predominantly on SMP and always
somewhere inside softirq processing.
[...]
Fix this by calling nap_adjust_return() inside DEFINE_INTERRUPT_HANDLER_ASYNC
immediately before irq_exit_rcu(), ensuring _TLF_NAPPING is cleared and
regs->NIP is adjusted before any code that can re-enable interrupts or
invoke softirqs runs.  Move the explanatory comment into
nap_adjust_return() itself and remove it from arch_interrupt_async_exit_prepare().

Fixes: bee25f97ad24 ("powerpc: Enable GENERIC_ENTRY feature")
Closes: https://lore.kernel.org/all/87wlvazrdy.fsf@igel.home/ (local)
Reported-by: Andreas Schwab <redacted>
Signed-off-by: Mukesh Kumar Chaurasiya (IBM) <redacted>

Tested-by: John Ogness <john.ogness@linutronix.de>

Is there a reason this is not being queued for 7.2? Without this fix,
PPC970 machines cannot boot 7.2.

Wondering the same. Quick reminder: Linus afaik wants all regressions
ideally be fixed by -rc6. So it would be good to get this mainlined
within the next few days -- unless of course there is a reason why this
fix is a bad idea. Is there?

I have added this to my fixes-test and will pull this as part of 
upcoming fixes PR
Maddy

Ciao, Thorsten