[RFC QEMU PATCH v5 1/1] xen: Use gsi instead of irq for mapping pirq

[Jiqian Chen]

In PVH dom0, it uses the linux local interrupt mechanism,
when it allocs irq for a gsi, it is dynamic, and follow
the principle of applying first, distributing first. And
the irq number is alloced from small to large, but the
applying gsi number is not, may gsi 38 comes before gsi
28, that causes the irq number is not equal with the gsi
number. And when passthrough a device, qemu wants to use
gsi to map pirq, xen_pt_realize->xc_physdev_map_pirq, but
the gsi number is got from file
/sys/bus/pci/devices/<sbdf>/irq in current code, so it
will fail when mapping.

Add gsi into XenHostPCIDevice and use gsi number that
read from gsi sysfs if it exists.

Signed-off-by: Huang Rui <ray.huang@amd.com>
Signed-off-by: Jiqian Chen <Jiqian.Chen@amd.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>

---
RFC: discussions ongoing on the Linux side where/how to expose the gsi

---
 hw/xen/xen-host-pci-device.c | 7 +++++++
 hw/xen/xen-host-pci-device.h | 1 +
 hw/xen/xen_pt.c              | 6 +++++-
 3 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/hw/xen/xen-host-pci-device.c b/hw/xen/xen-host-pci-device.c
index 8c6e9a1716a2..5be3279aa25b 100644
--- a/hw/xen/xen-host-pci-device.c
+++ b/hw/xen/xen-host-pci-device.c
@@ -370,6 +370,13 @@ void xen_host_pci_device_get(XenHostPCIDevice *d, uint16_t 
domain,
     }
     d->irq = v;
 
+    xen_host_pci_get_dec_value(d, "gsi", &v, errp);
+    if (*errp) {
+        d->gsi = -1;
+    } else {
+        d->gsi = v;
+    }
+
     xen_host_pci_get_hex_value(d, "class", &v, errp);
     if (*errp) {
         goto error;
diff --git a/hw/xen/xen-host-pci-device.h b/hw/xen/xen-host-pci-device.h
index 4d8d34ecb024..74c552bb5548 100644
--- a/hw/xen/xen-host-pci-device.h
+++ b/hw/xen/xen-host-pci-device.h
@@ -27,6 +27,7 @@ typedef struct XenHostPCIDevice {
     uint16_t device_id;
     uint32_t class_code;
     int irq;
+    int gsi;
 
     XenHostPCIIORegion io_regions[PCI_NUM_REGIONS - 1];
     XenHostPCIIORegion rom;
diff --git a/hw/xen/xen_pt.c b/hw/xen/xen_pt.c
index 3635d1b39f79..d34a7a8764ab 100644
--- a/hw/xen/xen_pt.c
+++ b/hw/xen/xen_pt.c
@@ -840,7 +840,11 @@ static void xen_pt_realize(PCIDevice *d, Error **errp)
         goto out;
     }
 
-    machine_irq = s->real_device.irq;
+    if (s->real_device.gsi < 0) {
+        machine_irq = s->real_device.irq;
+    } else {
+        machine_irq = s->real_device.gsi;
+    }
     if (machine_irq == 0) {
         XEN_PT_LOG(d, "machine irq is 0\n");
         cmd |= PCI_COMMAND_INTX_DISABLE;
-- 
2.34.1