On Fri, Aug 21, 2020 at 02:25:02AM +0200, Thomas Gleixner wrote:

+static void ims_mask_irq(struct irq_data *data)
+{
+	struct msi_desc *desc = irq_data_get_msi_desc(data);
+	struct ims_array_slot __iomem *slot = desc->device_msi.priv_iomem;
+	u32 __iomem *ctrl = &slot->ctrl;
+
+	iowrite32(ioread32(ctrl) & ~IMS_VECTOR_CTRL_UNMASK, ctrl);

Just to be clear, this is exactly the sort of operation we can't do
with non-MSI interrupts. For a real PCI device to execute this it
would have to keep the data on die.

I saw the idxd driver was doing something like this, I assume it
avoids trouble because it is a fake PCI device integrated with the
CPU, not on a real PCI bus?

It is really nice to see irq_domain used properly in x86!

Thanks,
Jason