[Qemu-devel] [PATCH V2] hw/virtio-pci: fix virtio behaviour on modern (PCIe) machines

[Marcel Apfelbaum <marcel@redhat.com>]

Modern machines are expected to be used by newer setups with
modern guests aiming the use of the latest features.

Enable modern and disable legacy for virtio devices
plugged into PCIe ports (Root ports or Downstream ports).
Using the Virtio 1 mode will remove the limitation
of the number of devices that can be attached to a machine
by removing the need for the IO BAR.

Convert 'disable-modern' and 'disable-legacy' properties to OnOffAuto
with default Auto.

Signed-off-by: Marcel Apfelbaum <marcel@redhat.com>
---

Hi,

v1 -> v2:
  - Stick to existing defaults for old machine types (Michael S. Tsirkin)

If everyone agrees, I am thinking about getting it into 2.7
to avoid the ~15 virtio devices limitation per machine.

Notes:
   - The non PCIe machines behaviour should remain the same.
   - I hope is OK to make the disable-* properties OnOffAuto. Previous setups
     using them can be affected, but libvirt is not using them yet (as far as I know)
   - My tests were limited to checking all possible disable-* configurations (and make check for all archs)

Thanks,
Marcel

 hw/virtio/virtio-pci.c | 31 ++++++++++++++++++++++++-------
 hw/virtio/virtio-pci.h |  2 ++
 include/hw/compat.h    |  8 ++++++++
 3 files changed, 34 insertions(+), 7 deletions(-)

diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
index 2b34b43..ec9e84f 100644
--- a/hw/virtio/virtio-pci.c
+++ b/hw/virtio/virtio-pci.c
@@ -1716,6 +1716,8 @@ static void virtio_pci_realize(PCIDevice *pci_dev, Error **errp)
 {
     VirtIOPCIProxy *proxy = VIRTIO_PCI(pci_dev);
     VirtioPCIClass *k = VIRTIO_PCI_GET_CLASS(pci_dev);
+    bool pcie_port = (pci_bus_is_express(pci_dev->bus) &&
+                      !pci_bus_is_root(pci_dev->bus));
 
     /*
      * virtio pci bar layout used by default.
@@ -1766,8 +1768,23 @@ static void virtio_pci_realize(PCIDevice *pci_dev, Error **errp)
 
     address_space_init(&proxy->modern_as, &proxy->modern_cfg, "virtio-pci-cfg-as");
 
-    if (pci_is_express(pci_dev) && pci_bus_is_express(pci_dev->bus) &&
-        !pci_bus_is_root(pci_dev->bus)) {
+    if ((pcie_port && (proxy->disable_modern == ON_OFF_AUTO_AUTO))
+         || (proxy->disable_modern == ON_OFF_AUTO_OFF)) {
+        proxy->flags &= ~VIRTIO_PCI_FLAG_DISABLE_MODERN;
+        pci_dev->cap_present |= QEMU_PCI_CAP_EXPRESS;
+    } else {
+        proxy->flags |= VIRTIO_PCI_FLAG_DISABLE_MODERN;
+        pci_dev->cap_present &= ~QEMU_PCI_CAP_EXPRESS;
+    }
+
+    if ((pcie_port && (proxy->disable_legacy == ON_OFF_AUTO_AUTO))
+        || (proxy->disable_legacy == ON_OFF_AUTO_ON)) {
+        proxy->flags |= VIRTIO_PCI_FLAG_DISABLE_LEGACY;
+    } else {
+        proxy->flags &= ~VIRTIO_PCI_FLAG_DISABLE_LEGACY;
+    }
+
+    if (pcie_port && pci_is_express(pci_dev)) {
         int pos;
 
         pos = pcie_endpoint_cap_init(pci_dev, 0);
@@ -1821,10 +1838,10 @@ static void virtio_pci_reset(DeviceState *qdev)
 static Property virtio_pci_properties[] = {
     DEFINE_PROP_BIT("virtio-pci-bus-master-bug-migration", VirtIOPCIProxy, flags,
                     VIRTIO_PCI_FLAG_BUS_MASTER_BUG_MIGRATION_BIT, false),
-    DEFINE_PROP_BIT("disable-legacy", VirtIOPCIProxy, flags,
-                    VIRTIO_PCI_FLAG_DISABLE_LEGACY_BIT, false),
-    DEFINE_PROP_BIT("disable-modern", VirtIOPCIProxy, flags,
-                    VIRTIO_PCI_FLAG_DISABLE_MODERN_BIT, true),
+    DEFINE_PROP_ON_OFF_AUTO("disable-legacy", VirtIOPCIProxy, disable_legacy,
+                            ON_OFF_AUTO_AUTO),
+    DEFINE_PROP_ON_OFF_AUTO("disable-modern", VirtIOPCIProxy, disable_modern,
+                            ON_OFF_AUTO_AUTO),
     DEFINE_PROP_BIT("migrate-extra", VirtIOPCIProxy, flags,
                     VIRTIO_PCI_FLAG_MIGRATE_EXTRA_BIT, true),
     DEFINE_PROP_BIT("modern-pio-notify", VirtIOPCIProxy, flags,
@@ -1841,7 +1858,7 @@ static void virtio_pci_dc_realize(DeviceState *qdev, Error **errp)
     PCIDevice *pci_dev = &proxy->pci_dev;
 
     if (!(proxy->flags & VIRTIO_PCI_FLAG_DISABLE_PCIE) &&
-        !(proxy->flags & VIRTIO_PCI_FLAG_DISABLE_MODERN)) {
+        !(proxy->disable_modern == ON_OFF_AUTO_ON)) {
         pci_dev->cap_present |= QEMU_PCI_CAP_EXPRESS;
     }
 
diff --git a/hw/virtio/virtio-pci.h b/hw/virtio/virtio-pci.h
index e4548c2..4f219d4 100644
--- a/hw/virtio/virtio-pci.h
+++ b/hw/virtio/virtio-pci.h
@@ -144,6 +144,8 @@ struct VirtIOPCIProxy {
     uint32_t modern_mem_bar;
     int config_cap;
     uint32_t flags;
+    OnOffAuto disable_modern;
+    OnOffAuto disable_legacy;
     uint32_t class_code;
     uint32_t nvectors;
     uint32_t dfselect;
diff --git a/include/hw/compat.h b/include/hw/compat.h
index 9914e7a..1531399 100644
--- a/include/hw/compat.h
+++ b/include/hw/compat.h
@@ -6,6 +6,14 @@
         .driver   = "virtio-mmio",\
         .property = "format_transport_address",\
         .value    = "off",\
+    },{\
+        .driver   = "virtio-pci",\
+        .property = "disable-modern",\
+        .value    = "on",\
+    },{\
+        .driver   = "virtio-pci",\
+        .property = "disable-legacy",\
+        .value    = "off",\
     },
 
 #define HW_COMPAT_2_5 \
-- 
2.4.3