According to the PLIC specification[1], global interrupt sources are assigned small unsigned integer identifiers beginning at the value 1. An interrupt ID of 0 is reserved to mean "no interrupt".

The current plic_irq_resume() and plic_irq_suspend() functions incorrectly start the loop from index 0, which accesses the register space for the reserved interrupt ID 0.

Change the loop to start from index 1, skipping the reserved interrupt ID 0 as per the PLIC specification.

This prevents potential undefined behavior when accessing the reserved register space during suspend/resume cycles.

Link: https://github.com/riscv/riscv-plic-spec/releases/tag/1.0.0

Fixes: e80f0b6a2cf3 ("irqchip/irq-sifive-plic: Add syscore callbacks for hibernation") Co-developed-by: Jia Wang wangjia@ultrarisc.com Signed-off-by: Jia Wang wangjia@ultrarisc.com Co-developed-by: Charles Mirabile cmirabil@redhat.com Signed-off-by: Charles Mirabile cmirabil@redhat.com Signed-off-by: Lucas Zampieri lzampier@redhat.com --- drivers/irqchip/irq-sifive-plic.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/irqchip/irq-sifive-plic.c b/drivers/irqchip/irq-sifive-plic.c index bf69a4802b71e..9c4af7d588463 100644 --- a/drivers/irqchip/irq-sifive-plic.c +++ b/drivers/irqchip/irq-sifive-plic.c @@ -252,7 +252,8 @@ static int plic_irq_suspend(void)

priv = per_cpu_ptr(&plic_handlers, smp_processor_id())->priv;

- for (i = 0; i < priv->nr_irqs; i++) { + /* irq ID 0 is reserved */ + for (i = 1; i < priv->nr_irqs; i++) { __assign_bit(i, priv->prio_save, readl(priv->regs + PRIORITY_BASE + i * PRIORITY_PER_ID)); } @@ -283,7 +284,8 @@ static void plic_irq_resume(void)

priv = per_cpu_ptr(&plic_handlers, smp_processor_id())->priv;

- for (i = 0; i < priv->nr_irqs; i++) { + /* irq ID 0 is reserved */ + for (i = 1; i < priv->nr_irqs; i++) { index = BIT_WORD(i); writel((priv->prio_save[index] & BIT_MASK(i)) ? 1 : 0, priv->regs + PRIORITY_BASE + i * PRIORITY_PER_ID);