[XEN PATCH v11 3/8] x86/pvh: Add PHYSDEVOP_setup_gsi for PVH dom0

[Jiqian Chen <Jiqian.Chen@xxxxxxx>]

The gsi of a passthrough device must be configured for it to be
able to be mapped into a hvm domU.
But When dom0 is PVH, the gsis don't get registered, it causes
the info of apic, pin and irq not be added into irq_2_pin list,
and the handler of irq_desc is not set, then when passthrough a
device, setting ioapic affinity and vector will fail.

To fix above problem, on Linux kernel side, a new code will
need to call PHYSDEVOP_setup_gsi for passthrough devices to
register gsi when dom0 is PVH.

So, add PHYSDEVOP_setup_gsi into hvm_physdev_op for above
purpose.

Clarify two questions:
First, why the gsi of devices belong to PVH dom0 can work?
Because when probe a driver to a normal device, it calls(on linux
kernel side) pci_device_probe-> request_threaded_irq->
irq_startup-> __unmask_ioapic-> io_apic_write, then trap into xen
side hvmemul_do_io-> hvm_io_intercept-> hvm_process_io_intercept->
vioapic_write_indirect-> vioapic_hwdom_map_gsi-> mp_register_gsi.
So that the gsi can be registered.

Second, why the gsi of passthrough device can't work when dom0
is PVH?
Because when assign a device to passthrough, it uses pciback to
probe the device, and it calls pcistub_probe->pcistub_seize->
pcistub_init_device-> xen_pcibk_reset_device->
xen_pcibk_control_isr->isr_on, but isr_on is not set, so that the
fake IRQ handler is not installed, then the gsi isn't unmasked.
What's more, we can see on Xen side, the function
vioapic_hwdom_map_gsi-> mp_register_gsi will be called only when
the gsi is unmasked, so that the gsi can't work for passthrough
device.

Signed-off-by: Jiqian Chen <Jiqian.Chen@xxxxxxx>
Signed-off-by: Huang Rui <ray.huang@xxxxxxx>
Signed-off-by: Jiqian Chen <Jiqian.Chen@xxxxxxx>
---
 xen/arch/x86/hvm/hypercall.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/xen/arch/x86/hvm/hypercall.c b/xen/arch/x86/hvm/hypercall.c
index 03ada3c880bd..cfe82d0f96ed 100644
--- a/xen/arch/x86/hvm/hypercall.c
+++ b/xen/arch/x86/hvm/hypercall.c
@@ -86,6 +86,7 @@ long hvm_physdev_op(int cmd, XEN_GUEST_HANDLE_PARAM(void) arg)
             return -ENOSYS;
         break;
 
+    case PHYSDEVOP_setup_gsi:
     case PHYSDEVOP_pci_mmcfg_reserved:
     case PHYSDEVOP_pci_device_add:
     case PHYSDEVOP_pci_device_remove:
-- 
2.34.1