vfio-pci: Add PCIe capability mangling based on bus type

Windows seems to pay particular interest to the PCIe header type of
devices and will fail to load drivers if we attach Endpoint devices or
Legacy Endpoint devices to the Root Complex.  We can use
pci_bus_is_express and pci_bus_is_root to determine the bus type and
mangle the type appropriately:

* Legacy PCI
  * No change, capability is unmodified for compatibility.
* PCI Express
  * Integrated Root Complex Endpoint -> Endpoint
* PCI Express Root Complex
  * Endpoint -> Integrated Root Complex Endpoint
  * Legacy Endpoint -> none, capability hidden

We also take this opportunity to explicitly limit supported devices
to Endpoints, Legacy Endpoints, and Root Complex Integrated Endpoints.
We don't currently have support for other types and users often cause
themselves problems by assigning them.
Signed-off-by: NAlex Williamson <alex.williamson@redhat.com>

hw/vfio_pci.c

@@ -1506,6 +1506,124 @@ static uint8_t vfio_std_cap_max_size(PCIDevice *pdev, uint8_t pos)
     return next - pos;
 }
 
+static void vfio_set_word_bits(uint8_t *buf, uint16_t val, uint16_t mask)
+{
+    pci_set_word(buf, (pci_get_word(buf) & ~mask) | val);
+}
+
+static void vfio_add_emulated_word(VFIODevice *vdev, int pos,
+                                   uint16_t val, uint16_t mask)
+{
+    vfio_set_word_bits(vdev->pdev.config + pos, val, mask);
+    vfio_set_word_bits(vdev->pdev.wmask + pos, ~mask, mask);
+    vfio_set_word_bits(vdev->emulated_config_bits + pos, mask, mask);
+}
+
+static void vfio_set_long_bits(uint8_t *buf, uint32_t val, uint32_t mask)
+{
+    pci_set_long(buf, (pci_get_long(buf) & ~mask) | val);
+}
+
+static void vfio_add_emulated_long(VFIODevice *vdev, int pos,
+                                   uint32_t val, uint32_t mask)
+{
+    vfio_set_long_bits(vdev->pdev.config + pos, val, mask);
+    vfio_set_long_bits(vdev->pdev.wmask + pos, ~mask, mask);
+    vfio_set_long_bits(vdev->emulated_config_bits + pos, mask, mask);
+}
+
+static int vfio_setup_pcie_cap(VFIODevice *vdev, int pos, uint8_t size)
+{
+    uint16_t flags;
+    uint8_t type;
+
+    flags = pci_get_word(vdev->pdev.config + pos + PCI_CAP_FLAGS);
+    type = (flags & PCI_EXP_FLAGS_TYPE) >> 4;
+
+    if (type != PCI_EXP_TYPE_ENDPOINT &&
+        type != PCI_EXP_TYPE_LEG_END &&
+        type != PCI_EXP_TYPE_RC_END) {
+
+        error_report("vfio: Assignment of PCIe type 0x%x "
+                     "devices is not currently supported", type);
+        return -EINVAL;
+    }
+
+    if (!pci_bus_is_express(vdev->pdev.bus)) {
+        /*
+         * Use express capability as-is on PCI bus.  It doesn't make much
+         * sense to even expose, but some drivers (ex. tg3) depend on it
+         * and guests don't seem to be particular about it.  We'll need
+         * to revist this or force express devices to express buses if we
+         * ever expose an IOMMU to the guest.
+         */
+    } else if (pci_bus_is_root(vdev->pdev.bus)) {
+        /*
+         * On a Root Complex bus Endpoints become Root Complex Integrated
+         * Endpoints, which changes the type and clears the LNK & LNK2 fields.
+         */
+        if (type == PCI_EXP_TYPE_ENDPOINT) {
+            vfio_add_emulated_word(vdev, pos + PCI_CAP_FLAGS,
+                                   PCI_EXP_TYPE_RC_END << 4,
+                                   PCI_EXP_FLAGS_TYPE);
+
+            /* Link Capabilities, Status, and Control goes away */
+            if (size > PCI_EXP_LNKCTL) {
+                vfio_add_emulated_long(vdev, pos + PCI_EXP_LNKCAP, 0, ~0);
+                vfio_add_emulated_word(vdev, pos + PCI_EXP_LNKCTL, 0, ~0);
+                vfio_add_emulated_word(vdev, pos + PCI_EXP_LNKSTA, 0, ~0);
+
+#ifndef PCI_EXP_LNKCAP2
+#define PCI_EXP_LNKCAP2 44
+#endif
+#ifndef PCI_EXP_LNKSTA2
+#define PCI_EXP_LNKSTA2 50
+#endif
+                /* Link 2 Capabilities, Status, and Control goes away */
+                if (size > PCI_EXP_LNKCAP2) {
+                    vfio_add_emulated_long(vdev, pos + PCI_EXP_LNKCAP2, 0, ~0);
+                    vfio_add_emulated_word(vdev, pos + PCI_EXP_LNKCTL2, 0, ~0);
+                    vfio_add_emulated_word(vdev, pos + PCI_EXP_LNKSTA2, 0, ~0);
+                }
+            }
+
+        } else if (type == PCI_EXP_TYPE_LEG_END) {
+            /*
+             * Legacy endpoints don't belong on the root complex.  Windows
+             * seems to be happier with devices if we skip the capability.
+             */
+            return 0;
+        }
+
+    } else {
+        /*
+         * Convert Root Complex Integrated Endpoints to regular endpoints.
+         * These devices don't support LNK/LNK2 capabilities, so make them up.
+         */
+        if (type == PCI_EXP_TYPE_RC_END) {
+            vfio_add_emulated_word(vdev, pos + PCI_CAP_FLAGS,
+                                   PCI_EXP_TYPE_ENDPOINT << 4,
+                                   PCI_EXP_FLAGS_TYPE);
+            vfio_add_emulated_long(vdev, pos + PCI_EXP_LNKCAP,
+                                   PCI_EXP_LNK_MLW_1 | PCI_EXP_LNK_LS_25, ~0);
+            vfio_add_emulated_word(vdev, pos + PCI_EXP_LNKCTL, 0, ~0);
+        }
+
+        /* Mark the Link Status bits as emulated to allow virtual negotiation */
+        vfio_add_emulated_word(vdev, pos + PCI_EXP_LNKSTA,
+                               pci_get_word(vdev->pdev.config + pos +
+                                            PCI_EXP_LNKSTA),
+                               PCI_EXP_LNKCAP_MLW | PCI_EXP_LNKCAP_SLS);
+    }
+
+    pos = pci_add_capability(&vdev->pdev, PCI_CAP_ID_EXP, pos, size);
+    if (pos >= 0) {
+        vdev->pdev.exp.exp_cap = pos;
+    }
+
+    return pos;
+}
+
 static int vfio_add_std_cap(VFIODevice *vdev, uint8_t pos)
 {
     PCIDevice *pdev = &vdev->pdev;
@@ -1536,13 +1654,22 @@ static int vfio_add_std_cap(VFIODevice *vdev, uint8_t pos)
             return ret;
         }
     } else {
-        pdev->config[PCI_CAPABILITY_LIST] = 0; /* Begin the rebuild */
+        /* Begin the rebuild, use QEMU emulated list bits */
+        pdev->config[PCI_CAPABILITY_LIST] = 0;
+        vdev->emulated_config_bits[PCI_CAPABILITY_LIST] = 0xff;
+        vdev->emulated_config_bits[PCI_STATUS] |= PCI_STATUS_CAP_LIST;
     }
 
+    /* Use emulated next pointer to allow dropping caps */
+    pci_set_byte(vdev->emulated_config_bits + pos + 1, 0xff);
+
     switch (cap_id) {
     case PCI_CAP_ID_MSI:
         ret = vfio_setup_msi(vdev, pos);
         break;
+    case PCI_CAP_ID_EXP:
+        ret = vfio_setup_pcie_cap(vdev, pos, size);
+        break;
     case PCI_CAP_ID_MSIX:
         ret = vfio_setup_msix(vdev, pos);
         break;