[PATCH 3/5] irqchip/riscv-imsic: Use wmb() to order normal writes and IPI writes

Xu Lu
2025-01-13T15:53:00Z

During an IPI procedure, we need to ensure all previous write operations
are visible to other CPUs before sending a real IPI. We use wmb() barrier
to ensure this as IMSIC issues IPI via mmio writes.

Signed-off-by: Xu Lu <luxu.kernel@bytedance.com>
---
drivers/irqchip/irq-riscv-imsic-early.c | 6 ++++++
1 file changed, 6 insertions(+)

diff --git a/drivers/irqchip/irq-riscv-imsic-early.c b/drivers/irqchip/irq-riscv-imsic-early.c
index 63097f2bbadf..c6317cb557fb 100644
--- a/drivers/irqchip/irq-riscv-imsic-early.c
+++ b/drivers/irqchip/irq-riscv-imsic-early.c
@@ -29,6 +29,12 @@ static void imsic_ipi_send(unsigned int cpu)
{
struct imsic_local_config *local = per_cpu_ptr(imsic->global.local, cpu);

+ /*
+ * Ensure that stores to normal memory are visible to the other CPUs
+ * before issuing IPI.
+ */
+ wmb();
+
writel_relaxed(IMSIC_IPI_ID, local->msi_va);
}

--
2.20.1