On Mon, Feb 25, 2019 at 01:10:12PM +1100, David Gibson wrote:

On Fri, Feb 22, 2019 at 12:28:28PM +0100, Cédric Le Goater wrote:

quoted

+	/*
+	 * If the source doesn't already have an IPI, allocate
+	 * one and get the corresponding data
+	 */
+	if (!state->ipi_number) {
+		state->ipi_number = xive_native_alloc_irq();
+		if (state->ipi_number == 0) {
+			pr_err("Failed to allocate IRQ !\n");
+			return -ENXIO;
+		}
+		xive_native_populate_irq_data(state->ipi_number,
+					      &state->ipi_data);
+		pr_debug("%s allocated hw_irq=0x%x for irq=0x%lx\n", __func__,
+			 state->ipi_number, irq);
+	}
+
+	arch_spin_lock(&sb->lock);

Why the direct call to arch_spin_lock() rather than just spin_lock()?

He's sharing data structures with the xics-on-xive code, and that code
has a real-mode variant, and in real mode we don't want to risk
invoking lockdep code.  Hence sb->lock is an arch_spinlock_t, and he
has to use arch_spin_lock() on it.

Paul.