[QEMU PATCH v8] xen/passthrough: use gsi to map pirq when dom0 is PVH

[Jiqian Chen <Jiqian.Chen@xxxxxxx>]

In PVH dom0, when passthrough a device to domU, QEMU code
xen_pt_realize->xc_physdev_map_pirq wants to use gsi, but in current codes
the gsi number is got from file /sys/bus/pci/devices/<sbdf>/irq, that is
wrong, because irq is not equal with gsi, they are in different spaces, so
pirq mapping fails.

To solve above problem, use new interface of Xen, xc_pcidev_get_gsi to get
gsi and use xc_physdev_map_pirq_gsi to map pirq when dom0 is PVH.

Signed-off-by: Jiqian Chen <Jiqian.Chen@xxxxxxx>
Signed-off-by: Huang Rui <ray.huang@xxxxxxx>
Signed-off-by: Jiqian Chen <Jiqian.Chen@xxxxxxx>
---
Hi All,
This is v8 to support passthrough on Xen when dom0 is PVH.
v7->v8 change:
* Since xc_physdev_gsi_from_dev was renamed to xc_pcidev_get_gsi, changed it.
* Added xen_run_qemu_on_hvm to check if Qemu run on PV dom0, if not use 
xc_physdev_map_pirq_gsi to map pirq.
* Used CONFIG_XEN_CTRL_INTERFACE_VERSION to wrap the new part for compatibility.
* Added "#define DOMID_RUN_QEMU 0" to represent the id of domain that Qemu run 
on.


Best regards,
Jiqian Chen



v6->v7 changes:
* Because the function of obtaining gsi was changed on the kernel and Xen side. 
Changed to use
  xc_physdev_gsi_from_dev, that requires passing in sbdf instead of irq.

v5->v6 changes:
* Because the function of obtaining gsi was changed on the kernel and Xen side. 
Changed to use
  xc_physdev_gsi_from_irq, instead of gsi sysfs.
* Since function changed, removed the Review-by of Stefano.

v4->v5 changes:
* Added Review-by Stefano.

v3->v4 changes:
* Added gsi into struct XenHostPCIDevice and used gsi number that read from gsi 
sysfs
  if it exists, if there is no gsi sysfs, still use irq.

v2->v3 changes:
* Due to changes in the implementation of the second patch on kernel side(that 
adds
  a new sysfs for gsi instead of a new syscall), so read gsi number from the 
sysfs of gsi.

v1 and v2:
We can record the relation between gsi and irq, then when userspace(qemu) want
to use gsi, we can do a translation. The third patch of kernel(xen/privcmd: Add 
new syscall
to get gsi from irq) records all the relations in acpi_register_gsi_xen_pvh() 
when dom0
initialize pci devices, and provide a syscall for userspace to get the gsi from 
irq. The
third patch of xen(tools: Add new function to get gsi from irq) add a new 
function
xc_physdev_gsi_from_irq() to call the new syscall added on kernel side.
And then userspace can use that function to get gsi. Then xc_physdev_map_pirq() 
will success.

Issues we encountered:
1. failed to map pirq for gsi
Problem: qemu will call xc_physdev_map_pirq() to map a passthrough device's gsi 
to pirq in
function xen_pt_realize(). But failed.

Reason: According to the implement of xc_physdev_map_pirq(), it needs gsi 
instead of irq,
but qemu pass irq to it and treat irq as gsi, it is got from file
/sys/bus/pci/devices/xxxx:xx:xx.x/irq in function xen_host_pci_device_get(). 
But actually
the gsi number is not equal with irq. They are in different space.
---
 hw/xen/xen_pt.c | 44 ++++++++++++++++++++++++++++++++++++++++++++
 hw/xen/xen_pt.h |  1 +
 2 files changed, 45 insertions(+)

diff --git a/hw/xen/xen_pt.c b/hw/xen/xen_pt.c
index 3635d1b39f79..7f8139d20915 100644
--- a/hw/xen/xen_pt.c
+++ b/hw/xen/xen_pt.c
@@ -766,6 +766,41 @@ static void xen_pt_destroy(PCIDevice *d) {
 }
 /* init */
 
+#define PCI_SBDF(seg, bus, dev, func) \
+            ((((uint32_t)(seg)) << 16) | \
+            (PCI_BUILD_BDF(bus, PCI_DEVFN(dev, func))))
+
+#if CONFIG_XEN_CTRL_INTERFACE_VERSION >= 42000
+static bool xen_run_qemu_on_hvm(void)
+{
+    xc_domaininfo_t info;
+
+    if (!xc_domain_getinfo_single(xen_xc, DOMID_RUN_QEMU, &info) &&
+        (info.flags & XEN_DOMINF_hvm_guest)) {
+        return true;
+    }
+
+    return false;
+}
+
+static int xen_map_pirq_for_gsi(PCIDevice *d, int *pirq)
+{
+    int gsi;
+    XenPCIPassthroughState *s = XEN_PT_DEVICE(d);
+
+    gsi = xc_pcidev_get_gsi(xen_xc,
+                            PCI_SBDF(s->real_device.domain,
+                                     s->real_device.bus,
+                                     s->real_device.dev,
+                                     s->real_device.func));
+    if (gsi >= 0) {
+        return xc_physdev_map_pirq_gsi(xen_xc, xen_domid, gsi, pirq);
+    }
+
+    return gsi;
+}
+#endif
+
 static void xen_pt_realize(PCIDevice *d, Error **errp)
 {
     ERRP_GUARD();
@@ -847,7 +882,16 @@ static void xen_pt_realize(PCIDevice *d, Error **errp)
         goto out;
     }
 
+#if CONFIG_XEN_CTRL_INTERFACE_VERSION >= 42000
+    if (xen_run_qemu_on_hvm()) {
+        rc = xen_map_pirq_for_gsi(d, &pirq);
+    } else {
+        rc = xc_physdev_map_pirq(xen_xc, xen_domid, machine_irq, &pirq);
+    }
+#else
     rc = xc_physdev_map_pirq(xen_xc, xen_domid, machine_irq, &pirq);
+#endif
+
     if (rc < 0) {
         XEN_PT_ERR(d, "Mapping machine irq %u to pirq %i failed, (err: %d)\n",
                    machine_irq, pirq, errno);
diff --git a/hw/xen/xen_pt.h b/hw/xen/xen_pt.h
index 095a0f0365d4..a08b45b7fbae 100644
--- a/hw/xen/xen_pt.h
+++ b/hw/xen/xen_pt.h
@@ -36,6 +36,7 @@ void xen_pt_log(const PCIDevice *d, const char *f, ...) 
G_GNUC_PRINTF(2, 3);
 #  define XEN_PT_LOG_CONFIG(d, addr, val, len)
 #endif
 
+#define DOMID_RUN_QEMU 0
 
 /* Helper */
 #define XEN_PFN(x) ((x) >> XC_PAGE_SHIFT)
-- 
2.34.1