Re: [Qemu-devel] [PATCH] virtio-pci: Add Function Level Reset support

[Julia Suvorova <jusual@redhat.com>]

On Fri, Aug 9, 2019 at 6:35 PM Michael S. Tsirkin <mst@redhat.com> wrote:
>
> On Wed, Aug 07, 2019 at 10:22:41AM +0200, Julia Suvorova wrote:
> > Using FLR becomes convenient in cases where resetting the bus is
> > impractical, for example, when debugging the behavior of individual
> > functions.
> >
> > Signed-off-by: Julia Suvorova <jusual@redhat.com>
> > ---
> >  hw/virtio/virtio-pci.c | 10 ++++++++++
> >  hw/virtio/virtio-pci.h |  1 +
> >  2 files changed, 11 insertions(+)
> >
> > diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
> > index f6d2223e78..37c5d6efbc 100644
> > --- a/hw/virtio/virtio-pci.c
> > +++ b/hw/virtio/virtio-pci.c
> > @@ -599,6 +599,10 @@ static void virtio_write_config(PCIDevice *pci_dev, uint32_t address,
> >
> >      pci_default_write_config(pci_dev, address, val, len);
> >
> > +    if (proxy->has_flr) {
> > +        pcie_cap_flr_write_config(pci_dev, address, val, len);
> > +    }
> > +
> >      if (range_covers_byte(address, len, PCI_COMMAND) &&
> >          !(pci_dev->config[PCI_COMMAND] & PCI_COMMAND_MASTER)) {
> >          virtio_pci_stop_ioeventfd(proxy);
> > @@ -1718,6 +1722,8 @@ static void virtio_pci_realize(PCIDevice *pci_dev, Error **errp)
> >      proxy->notify_pio.size = 0x4;
> >      proxy->notify_pio.type = VIRTIO_PCI_CAP_NOTIFY_CFG;
> >
> > +    proxy->has_flr = false;
> > +
> >      /* subclasses can enforce modern, so do this unconditionally */
> >      memory_region_init(&proxy->modern_bar, OBJECT(proxy), "virtio-pci",
> >                         /* PCI BAR regions must be powers of 2 */
> > @@ -1749,6 +1755,10 @@ static void virtio_pci_realize(PCIDevice *pci_dev, Error **errp)
> >
> >          pci_dev->exp.pm_cap = pos;
> >
> > +        /* Set Function Level Reset capability bit */
> > +        pcie_cap_flr_init(pci_dev);
> > +        proxy->has_flr = true;
> > +
> >          /*
> >           * Indicates that this function complies with revision 1.2 of the
> >           * PCI Power Management Interface Specification.
>
>
> I don't think we can set this for everyone: this will break
> things like cross version migration.

I see. If I add a flag and a property, which version of hw_compat should I use?

Best regards, Julia Suvorova.