Re: [Qemu-devel] [PATCH V3] hw/virtio-pci: fix virtio behaviour

["Michael S. Tsirkin" <mst@redhat.com>]

On Wed, Jul 20, 2016 at 06:28:21PM +0300, Marcel Apfelbaum wrote:
> Enable transitional virtio devices by default.
> Enable virtio-1.0 for 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.
> 
> Signed-off-by: Marcel Apfelbaum <marcel@redhat.com>
> ---
> 
> Hi,
> 
> v2 -> v3:
>   - Various code tweaks to simplify if statements (Michael)
>   - Enable virtio modern by default (Gerd and Cornelia)
>   - Replace virtio flags with actual fields (Gerd)
>   - Wrappers for more readable code
> 
> v1 -> v2:
>   - Stick to existing defaults for old machine types (Michael S. Tsirkin)

Actually this can still break existing scripts:
stick a device on express bus but add disable-modern=on
Gave you a legacy device previously but it no longer does.

> If everyone agrees, I am thinking about getting it into 2.7
> to avoid the ~15 virtio devices limitation per machine.
> 
> My tests were limited to checking all possible disable-* configurations (and make check for all archs)
> 
> Thanks,
> Marcel
> 
>  hw/display/virtio-gpu-pci.c |  4 +---
>  hw/display/virtio-vga.c     |  4 +---
>  hw/virtio/virtio-pci.c      | 34 ++++++++++++++++++----------------
>  hw/virtio/virtio-pci.h      | 21 +++++++++++++++++----
>  include/hw/compat.h         |  8 ++++++++
>  5 files changed, 45 insertions(+), 26 deletions(-)
> 
> diff --git a/hw/display/virtio-gpu-pci.c b/hw/display/virtio-gpu-pci.c
> index a71b230..34a724c 100644
> --- a/hw/display/virtio-gpu-pci.c
> +++ b/hw/display/virtio-gpu-pci.c
> @@ -30,9 +30,7 @@ static void virtio_gpu_pci_realize(VirtIOPCIProxy *vpci_dev, Error **errp)
>      int i;
>  
>      qdev_set_parent_bus(vdev, BUS(&vpci_dev->bus));
> -    /* force virtio-1.0 */
> -    vpci_dev->flags &= ~VIRTIO_PCI_FLAG_DISABLE_MODERN;
> -    vpci_dev->flags |= VIRTIO_PCI_FLAG_DISABLE_LEGACY;
> +    virtio_pci_force_virtio_1(vpci_dev);
>      object_property_set_bool(OBJECT(vdev), true, "realized", errp);
>  
>      for (i = 0; i < g->conf.max_outputs; i++) {
> diff --git a/hw/display/virtio-vga.c b/hw/display/virtio-vga.c
> index 315b7fc..5b510a1 100644
> --- a/hw/display/virtio-vga.c
> +++ b/hw/display/virtio-vga.c
> @@ -134,9 +134,7 @@ static void virtio_vga_realize(VirtIOPCIProxy *vpci_dev, Error **errp)
>  
>      /* init virtio bits */
>      qdev_set_parent_bus(DEVICE(g), BUS(&vpci_dev->bus));
> -    /* force virtio-1.0 */
> -    vpci_dev->flags &= ~VIRTIO_PCI_FLAG_DISABLE_MODERN;
> -    vpci_dev->flags |= VIRTIO_PCI_FLAG_DISABLE_LEGACY;
> +    virtio_pci_force_virtio_1(vpci_dev);
>      object_property_set_bool(OBJECT(g), true, "realized", &err);
>      if (err) {
>          error_propagate(errp, err);
> diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
> index 2b34b43..11cd634 100644
> --- a/hw/virtio/virtio-pci.c
> +++ b/hw/virtio/virtio-pci.c
> @@ -161,7 +161,7 @@ static bool virtio_pci_modern_state_needed(void *opaque)
>  {
>      VirtIOPCIProxy *proxy = opaque;
>  
> -    return !(proxy->flags & VIRTIO_PCI_FLAG_DISABLE_MODERN);
> +    return virtio_pci_modern(proxy);
>  }
>  
>  static const VMStateDescription vmstate_virtio_pci_modern_state = {
> @@ -300,8 +300,8 @@ static int virtio_pci_ioeventfd_assign(DeviceState *d, EventNotifier *notifier,
>      VirtIOPCIProxy *proxy = to_virtio_pci_proxy(d);
>      VirtIODevice *vdev = virtio_bus_get_device(&proxy->bus);
>      VirtQueue *vq = virtio_get_queue(vdev, n);
> -    bool legacy = !(proxy->flags & VIRTIO_PCI_FLAG_DISABLE_LEGACY);
> -    bool modern = !(proxy->flags & VIRTIO_PCI_FLAG_DISABLE_MODERN);
> +    bool legacy = virtio_pci_legacy(proxy);
> +    bool modern = virtio_pci_modern(proxy);
>      bool fast_mmio = kvm_ioeventfd_any_length_enabled();
>      bool modern_pio = proxy->flags & VIRTIO_PCI_FLAG_MODERN_PIO_NOTIFY;
>      MemoryRegion *modern_mr = &proxy->notify.mr;
> @@ -1576,8 +1576,8 @@ static void virtio_pci_device_plugged(DeviceState *d, Error **errp)
>  {
>      VirtIOPCIProxy *proxy = VIRTIO_PCI(d);
>      VirtioBusState *bus = &proxy->bus;
> -    bool legacy = !(proxy->flags & VIRTIO_PCI_FLAG_DISABLE_LEGACY);
> -    bool modern = !(proxy->flags & VIRTIO_PCI_FLAG_DISABLE_MODERN);
> +    bool legacy = virtio_pci_legacy(proxy);
> +    bool modern = virtio_pci_modern(proxy);
>      bool modern_pio = proxy->flags & VIRTIO_PCI_FLAG_MODERN_PIO_NOTIFY;
>      uint8_t *config;
>      uint32_t size;
> @@ -1696,7 +1696,7 @@ static void virtio_pci_device_plugged(DeviceState *d, Error **errp)
>  static void virtio_pci_device_unplugged(DeviceState *d)
>  {
>      VirtIOPCIProxy *proxy = VIRTIO_PCI(d);
> -    bool modern = !(proxy->flags & VIRTIO_PCI_FLAG_DISABLE_MODERN);
> +    bool modern = virtio_pci_modern(proxy);
>      bool modern_pio = proxy->flags & VIRTIO_PCI_FLAG_MODERN_PIO_NOTIFY;
>  
>      virtio_pci_stop_ioeventfd(proxy);
> @@ -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 +1768,11 @@ 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 (proxy->disable_legacy == ON_OFF_AUTO_AUTO) {
> +        proxy->disable_legacy = pcie_port ? ON_OFF_AUTO_ON : ON_OFF_AUTO_OFF;
> +    }
> +
> +    if (pcie_port && pci_is_express(pci_dev)) {
>          int pos;
>  
>          pos = pcie_endpoint_cap_init(pci_dev, 0);
> @@ -1821,10 +1826,9 @@ 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_BOOL("disable-modern", VirtIOPCIProxy, disable_modern, false),
>      DEFINE_PROP_BIT("migrate-extra", VirtIOPCIProxy, flags,
>                      VIRTIO_PCI_FLAG_MIGRATE_EXTRA_BIT, true),
>      DEFINE_PROP_BIT("modern-pio-notify", VirtIOPCIProxy, flags,
> @@ -1841,7 +1845,7 @@ 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)) {
> +        virtio_pci_modern(proxy)) {
>          pci_dev->cap_present |= QEMU_PCI_CAP_EXPRESS;
>      }
>  
> @@ -2303,9 +2307,7 @@ static void virtio_input_pci_realize(VirtIOPCIProxy *vpci_dev, Error **errp)
>      DeviceState *vdev = DEVICE(&vinput->vdev);
>  
>      qdev_set_parent_bus(vdev, BUS(&vpci_dev->bus));
> -    /* force virtio-1.0 */
> -    vpci_dev->flags &= ~VIRTIO_PCI_FLAG_DISABLE_MODERN;
> -    vpci_dev->flags |= VIRTIO_PCI_FLAG_DISABLE_LEGACY;
> +    virtio_pci_force_virtio_1(vpci_dev);
>      object_property_set_bool(OBJECT(vdev), true, "realized", errp);
>  }
>  
> diff --git a/hw/virtio/virtio-pci.h b/hw/virtio/virtio-pci.h
> index e4548c2..25fbf8a 100644
> --- a/hw/virtio/virtio-pci.h
> +++ b/hw/virtio/virtio-pci.h
> @@ -61,8 +61,6 @@ typedef struct VirtioBusClass VirtioPCIBusClass;
>  enum {
>      VIRTIO_PCI_FLAG_BUS_MASTER_BUG_MIGRATION_BIT,
>      VIRTIO_PCI_FLAG_USE_IOEVENTFD_BIT,
> -    VIRTIO_PCI_FLAG_DISABLE_LEGACY_BIT,
> -    VIRTIO_PCI_FLAG_DISABLE_MODERN_BIT,
>      VIRTIO_PCI_FLAG_MIGRATE_EXTRA_BIT,
>      VIRTIO_PCI_FLAG_MODERN_PIO_NOTIFY_BIT,
>      VIRTIO_PCI_FLAG_DISABLE_PCIE_BIT,
> @@ -77,8 +75,6 @@ enum {
>  #define VIRTIO_PCI_FLAG_USE_IOEVENTFD   (1 << VIRTIO_PCI_FLAG_USE_IOEVENTFD_BIT)
>  
>  /* virtio version flags */
> -#define VIRTIO_PCI_FLAG_DISABLE_LEGACY (1 << VIRTIO_PCI_FLAG_DISABLE_LEGACY_BIT)
> -#define VIRTIO_PCI_FLAG_DISABLE_MODERN (1 << VIRTIO_PCI_FLAG_DISABLE_MODERN_BIT)
>  #define VIRTIO_PCI_FLAG_DISABLE_PCIE (1 << VIRTIO_PCI_FLAG_DISABLE_PCIE_BIT)
>  
>  /* migrate extra state */
> @@ -144,6 +140,8 @@ struct VirtIOPCIProxy {
>      uint32_t modern_mem_bar;
>      int config_cap;
>      uint32_t flags;
> +    bool disable_modern;
> +    OnOffAuto disable_legacy;
>      uint32_t class_code;
>      uint32_t nvectors;
>      uint32_t dfselect;
> @@ -158,6 +156,21 @@ struct VirtIOPCIProxy {
>      VirtioBusState bus;
>  };
>  
> +static inline bool virtio_pci_modern(VirtIOPCIProxy *proxy)
> +{
> +    return !proxy->disable_modern;
> +}
> +
> +static inline bool virtio_pci_legacy(VirtIOPCIProxy *proxy)
> +{
> +    return proxy->disable_legacy == ON_OFF_AUTO_OFF;
> +}
> +
> +static inline void virtio_pci_force_virtio_1(VirtIOPCIProxy *proxy)
> +{
> +    proxy->disable_modern = false;
> +    proxy->disable_legacy = ON_OFF_AUTO_ON;
> +}
>  
>  /*
>   * virtio-scsi-pci: This extends VirtioPCIProxy.
> 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