On Wed, Jan 27, 2021 at 12:23:45PM -0800, Michael Kelley wrote:
[...]

+static int hv_setup_stimer0_irq(void)
+{
+	int ret;
+
+	ret = acpi_register_gsi(NULL, HYPERV_STIMER0_VECTOR,
+			ACPI_EDGE_SENSITIVE, ACPI_ACTIVE_HIGH);

When IO-APIC is enabled on x86, acpi_register_gsi calls
mp_map_gsi_to_irq. That function then calls mp_find_ioapic. Is
HYPERV_STIMER0_VECTOR, when used as a GSI, associated with an IO-APIC?
If not, wouldn't mp_find_ioapic return an error causing
acpi_register_gsi to fail?

Ah, it appears that this function is not called on x86. I haven't
checked how ARM handles GSI, but presumably this works for you.  It
would be good if a comment can be added to clarify things.

Wei.