[RFC QEMU PATCH v7 1/1] xen/pci: get gsi for passthrough devices

[Jiqian Chen <Jiqian.Chen@xxxxxxx>]

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.

Get gsi by using new function supported by Xen tools.

Signed-off-by: Huang Rui <ray.huang@xxxxxxx>
Signed-off-by: Jiqian Chen <Jiqian.Chen@xxxxxxx>
---
 hw/xen/xen-host-pci-device.c | 19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

diff --git a/hw/xen/xen-host-pci-device.c b/hw/xen/xen-host-pci-device.c
index 8c6e9a1716a2..2fe6a60434ba 100644
--- a/hw/xen/xen-host-pci-device.c
+++ b/hw/xen/xen-host-pci-device.c
@@ -10,6 +10,7 @@
 #include "qapi/error.h"
 #include "qemu/cutils.h"
 #include "xen-host-pci-device.h"
+#include "hw/xen/xen_native.h"
 
 #define XEN_HOST_PCI_MAX_EXT_CAP \
     ((PCIE_CONFIG_SPACE_SIZE - PCI_CONFIG_SPACE_SIZE) / (PCI_CAP_SIZEOF + 4))
@@ -329,12 +330,17 @@ int xen_host_pci_find_ext_cap_offset(XenHostPCIDevice *d, 
uint32_t cap)
     return -1;
 }
 
+#define PCI_SBDF(seg, bus, dev, func) \
+            ((((uint32_t)(seg)) << 16) | \
+            (PCI_BUILD_BDF(bus, PCI_DEVFN(dev, func))))
+
 void xen_host_pci_device_get(XenHostPCIDevice *d, uint16_t domain,
                              uint8_t bus, uint8_t dev, uint8_t func,
                              Error **errp)
 {
     ERRP_GUARD();
     unsigned int v;
+    uint32_t sdbf;
 
     d->config_fd = -1;
     d->domain = domain;
@@ -364,11 +370,16 @@ void xen_host_pci_device_get(XenHostPCIDevice *d, 
uint16_t domain,
     }
     d->device_id = v;
 
-    xen_host_pci_get_dec_value(d, "irq", &v, errp);
-    if (*errp) {
-        goto error;
+    sdbf = PCI_SBDF(domain, bus, dev, func);
+    d->irq = xc_physdev_gsi_from_dev(xen_xc, sdbf);
+    /* fail to get gsi, fallback to irq */
+    if (d->irq == -1) {
+        xen_host_pci_get_dec_value(d, "irq", &v, errp);
+        if (*errp) {
+            goto error;
+        }
+        d->irq = v;
     }
-    d->irq = v;
 
     xen_host_pci_get_hex_value(d, "class", &v, errp);
     if (*errp) {
-- 
2.34.1