powerpc: Don't select HAVE_IRQ_EXIT_ON_IRQ_STACK

powerpc: Don't select HAVE_IRQ_EXIT_ON_IRQ_STACK

commit 5ec51de1c00af04615f2ad7a1f9199bcb160cfd0 upstream.

The HAVE_IRQ_EXIT_ON_IRQ_STACK option tells generic code that irq_exit()
is called while still running on the hard irq stack (hardirq_ctx[] in
the powerpc code).

Selecting the option means the generic code will *not* switch to the
softirq stack before running softirqs, because the code is already
running on the (mostly empty) hard irq stack.

But since commit 4ffc24648410 ("powerpc: handle irq_enter/irq_exit in
interrupt handler wrappers"), irq_exit() is now called on the regular task
stack, not the hard irq stack.

That's because previously irq_exit() was called in __do_irq() which is
run on the hard irq stack, but now it is called in
interrupt_async_exit_prepare() which is called from do_irq() constructed
by the wrapper macro, which is after the switch back to the task stack.

So drop HAVE_IRQ_EXIT_ON_IRQ_STACK from the Kconfig. This will mean an
extra stack switch when processing some interrupts, but should
significantly reduce the likelihood of stack overflow.

It also means the softirq stack will be used for running softirqs from
other interrupts that don't use the hard irq stack, eg. timer interrupts.

Fixes: 4ffc24648410 ("powerpc: handle irq_enter/irq_exit in interrupt handler wrappers")
Cc: stable@vger.kernel.org # v5.12+
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220525032639.1947280-1-mpe@ellerman.id.au
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>