[PULL,1/3] xen/passthrough: use gsi to map pirq when dom0 is PVH

Commit Message

Anthony PERARD March 10, 2025, 2:45 p.m. UTC

From: Jiqian Chen <[e-mail]>

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 <[e-mail]>
Signed-off-by: Huang Rui <[e-mail]>
Signed-off-by: Jiqian Chen <[e-mail]>
Acked-by: Anthony PERARD <[e-mail]>
Reviewed-by: Stewart Hildebrand <[e-mail]>
Message-Id: <[e-mail]>
Signed-off-by: Anthony PERARD <[e-mail]>
---
 hw/xen/xen_pt.c      | 60 ++++++++++++++++++++++++++++++++++++++++++++
 include/hw/pci/pci.h |  4 +++
 2 files changed, 64 insertions(+)

Patch

diff --git a/hw/xen/xen_pt.c b/hw/xen/xen_pt.c
index e2bd4c7d41..9487f68f2e 100644
--- a/hw/xen/xen_pt.c
+++ b/hw/xen/xen_pt.c
@@ -766,6 +766,57 @@  static void xen_pt_destroy(PCIDevice *d) {
 }
 /* init */
 
+#if CONFIG_XEN_CTRL_INTERFACE_VERSION >= 42000
+static bool xen_pt_need_gsi(void)
+{
+    FILE *fp;
+    int len;
+    /*
+     * The max length of guest_type is "PVH"+'\n'+'\0', it is 5,
+     * so here set the length of type to be twice.
+     */
+    char type[10];
+    const char *guest_type = "/sys/hypervisor/guest_type";
+
+    fp = fopen(guest_type, "r");
+    if (!fp) {
+        error_report("Cannot open %s: %s", guest_type, strerror(errno));
+        return false;
+    }
+
+    if (fgets(type, sizeof(type), fp)) {
+        len = strlen(type);
+        if (len) {
+            type[len - 1] = '\0';
+            if (!strcmp(type, "PVH")) {
+                fclose(fp);
+                return true;
+            }
+        }
+    }
+
+    fclose(fp);
+    return false;
+}
+
+static int xen_pt_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 +898,16 @@  static void xen_pt_realize(PCIDevice *d, Error **errp)
         goto out;
     }
 
+#if CONFIG_XEN_CTRL_INTERFACE_VERSION >= 42000
+    if (xen_pt_need_gsi()) {
+        rc = xen_pt_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/include/hw/pci/pci.h b/include/hw/pci/pci.h
index c220cc8449..822fbacdf0 100644
--- a/include/hw/pci/pci.h
+++ b/include/hw/pci/pci.h
@@ -23,6 +23,10 @@  extern bool pci_available;
 #define PCI_SLOT_MAX            32
 #define PCI_FUNC_MAX            8
 
+#define PCI_SBDF(seg, bus, dev, func) \
+            ((((uint32_t)(seg)) << 16) | \
+            (PCI_BUILD_BDF(bus, PCI_DEVFN(dev, func))))
+
 /* Class, Vendor and Device IDs from Linux's pci_ids.h */
 #include "hw/pci/pci_ids.h"