vfio/pci: detect the support of dynamic MSI-X allocation

Kernel provides the guidance of dynamic MSI-X allocation support of
passthrough device, by clearing the VFIO_IRQ_INFO_NORESIZE flag to
guide user space.

Fetch the flags from host to determine if dynamic MSI-X allocation is
supported.

Originally-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: Jing Liu <jing2.liu@intel.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Reviewed-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Cédric Le Goater <clg@redhat.com>

1 files changed, 14 insertions, 2 deletions

diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
index b2d5010b9f..86c92c51a4 100644
--- a/hw/vfio/pci.c
+++ b/hw/vfio/pci.c
@@ -1493,7 +1493,9 @@ static void vfio_msix_early_setup(VFIOPCIDevice *vdev, Error **errp)
     uint8_t pos;
     uint16_t ctrl;
     uint32_t table, pba;
-    int fd = vdev->vbasedev.fd;
+    int ret, fd = vdev->vbasedev.fd;
+    struct vfio_irq_info irq_info = { .argsz = sizeof(irq_info),
+                                      .index = VFIO_PCI_MSIX_IRQ_INDEX };
     VFIOMSIXInfo *msix;
 
     pos = pci_find_capability(&vdev->pdev, PCI_CAP_ID_MSIX);
@@ -1530,6 +1532,15 @@ static void vfio_msix_early_setup(VFIOPCIDevice *vdev, Error **errp)
     msix->pba_offset = pba & ~PCI_MSIX_FLAGS_BIRMASK;
     msix->entries = (ctrl & PCI_MSIX_FLAGS_QSIZE) + 1;
 
+    ret = ioctl(vdev->vbasedev.fd, VFIO_DEVICE_GET_IRQ_INFO, &irq_info);
+    if (ret < 0) {
+        error_setg_errno(errp, -ret, "failed to get MSI-X irq info");
+        g_free(msix);
+        return;
+    }
+
+    msix->noresize = !!(irq_info.flags & VFIO_IRQ_INFO_NORESIZE);
+
     /*
      * Test the size of the pba_offset variable and catch if it extends outside
      * of the specified BAR. If it is the case, we need to apply a hardware
@@ -1562,7 +1573,8 @@ static void vfio_msix_early_setup(VFIOPCIDevice *vdev, Error **errp)
     }
 
     trace_vfio_msix_early_setup(vdev->vbasedev.name, pos, msix->table_bar,
-                                msix->table_offset, msix->entries);
+                                msix->table_offset, msix->entries,
+                                msix->noresize);
     vdev->msix = msix;
 
     vfio_pci_fixup_msix_region(vdev);