[RFC PATCH] PCI: hv: Avoid the retarget interrupt hypercall in irq_unmask() on ARM64

[Boqun Feng]

On ARM64 Hyper-V guests, SPIs are used for the interrupts of virtual PCI
devices, and SPIs can be managed directly via GICD registers. Therefore
the retarget interrupt hypercall is not needed on ARM64.

The retarget interrupt hypercall related code is now put in a helper
function and only called on x86.

Signed-off-by: Boqun Feng <boqun.feng@xxxxxxxxx>
---
 drivers/pci/controller/pci-hyperv.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c
index 20ea2ee330b8..80aa33ef5bf0 100644
--- a/drivers/pci/controller/pci-hyperv.c
+++ b/drivers/pci/controller/pci-hyperv.c
@@ -1457,7 +1457,7 @@ static void hv_irq_mask(struct irq_data *data)
 }
 
 /**
- * hv_irq_unmask() - "Unmask" the IRQ by setting its current
+ * __hv_irq_unmask() - "Unmask" the IRQ by setting its current
  * affinity.
  * @data:	Describes the IRQ
  *
@@ -1466,7 +1466,7 @@ static void hv_irq_mask(struct irq_data *data)
  * is built out of this PCI bus's instance GUID and the function
  * number of the device.
  */
-static void hv_irq_unmask(struct irq_data *data)
+static void __hv_irq_unmask(struct irq_data *data)
 {
 	struct msi_desc *msi_desc = irq_data_get_msi_desc(data);
 	struct hv_retarget_device_interrupt *params;
@@ -1569,6 +1569,13 @@ static void hv_irq_unmask(struct irq_data *data)
 	if (!hv_result_success(res) && hbus->state != hv_pcibus_removing)
 		dev_err(&hbus->hdev->device,
 			"%s() failed: %#llx", __func__, res);
+}
+
+static void hv_irq_unmask(struct irq_data *data)
+{
+	/* Only use a hypercall on x86 */
+	if (IS_ENABLED(CONFIG_X86))
+		__hv_irq_unmask(data);
 
 	if (data->parent_data->chip->irq_unmask)
 		irq_chip_unmask_parent(data);
-- 
2.35.1