From: Christophe Leroy christophe.leroy@csgroup.eu
[ Upstream commit 0eb089a72fda3f7969e6277804bde75dc1474a14 ]
A disassembly of interrupt_exit_kernel_prepare() shows a useless read of MSR register. This is shown by r9 being re-used immediately without doing anything with the value read.
c000e0e0: 60 00 00 00 nop c000e0e4: 7d 3a c2 a6 mfmd_ap r9 c000e0e8: 7d 20 00 a6 mfmsr r9 c000e0ec: 7c 51 13 a6 mtspr 81,r2 c000e0f0: 81 3f 00 84 lwz r9,132(r31) c000e0f4: 71 29 80 00 andi. r9,r9,32768
This is due to the use of local_irq_save(). The flags read by local_irq_save() are never used, use local_irq_disable() instead.
Fixes: 13799748b957 ("powerpc/64: use interrupt restart table to speed up return from interrupt") Signed-off-by: Christophe Leroy christophe.leroy@csgroup.eu Reviewed-by: Nicholas Piggin npiggin@gmail.com Signed-off-by: Michael Ellerman mpe@ellerman.id.au Link: https://msgid.link/df36c6205ab64326fb1b991993c82057e92ace2f.1685955214.git.c... Signed-off-by: Sasha Levin sashal@kernel.org --- arch/powerpc/kernel/interrupt.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/arch/powerpc/kernel/interrupt.c b/arch/powerpc/kernel/interrupt.c index 0ec1581619db5..cf770d86c03c6 100644 --- a/arch/powerpc/kernel/interrupt.c +++ b/arch/powerpc/kernel/interrupt.c @@ -368,7 +368,6 @@ void preempt_schedule_irq(void);
notrace unsigned long interrupt_exit_kernel_prepare(struct pt_regs *regs) { - unsigned long flags; unsigned long ret = 0; unsigned long kuap; bool stack_store = read_thread_flags() & _TIF_EMULATE_STACK_STORE; @@ -392,7 +391,7 @@ notrace unsigned long interrupt_exit_kernel_prepare(struct pt_regs *regs)
kuap = kuap_get_and_assert_locked();
- local_irq_save(flags); + local_irq_disable();
if (!arch_irq_disabled_regs(regs)) { /* Returning to a kernel context with local irqs enabled. */