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

[Marcel Apfelbaum]

On 07/19/2016 08:47 PM, Michael S. Tsirkin wrote:
> On Tue, Jul 19, 2016 at 07:45:44PM +0300, Marcel Apfelbaum wrote:
> > 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 <address@hidden>
>
>
> Sounds good, but I think we need to stick to existing
> defaults for old machine types.
> Pls add compat entries accordingly.

Added and posted v2. Thanks for the quick review!
Marcel

> > ---
> >
> > Hi,
> >
> > 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 ++
> >   2 files changed, 26 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);
>
> down the road, I really think we need a new type of
> property that does not need this manual code.
> E.g. specify a location to store the bit.
>
> This can wait though.
>
>
> > @@ -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;
> > --
> > 2.4.3