Re: [Qemu-devel] [PATCH 13/15] virtio-pci: reset all qbuses too when writing to the status field

[Michael S. Tsirkin]

On Mon, Dec 17, 2012 at 05:54:06PM +0100, Paolo Bonzini wrote:
> Il 17/12/2012 17:48, Michael S. Tsirkin ha scritto:
> > On Mon, Dec 17, 2012 at 05:24:48PM +0100, Paolo Bonzini wrote:
> >> virtio-pci devices do not perform a full reset when zero is written
> >> to the status byte.  While PCI-specific status is initialized, the
> >> reset does not propagate down the qdev bus hierarchy.  Because of
> >> this, a virtio reset does not cancel in-flight I/O for virtio-scsi
> >> (where the cancellation is handled automatically by the SCSI
> >> devices underneath virtio-scsi-pci).
> >>
> >> Reported-by: Bryan Venteicher <address@hidden>
> >> Cc: Michael S. Tsirkin <address@hidden>
> >> Signed-off-by: Paolo Bonzini <address@hidden>
> > 
> > I would still prefer this logic to reside in virtio.c instead of being
> > duplicated in each bus.
> > My idea was to simply call qdev_reset_all on the binding from virtio.c
> > but other ideas wellcome.
> 
> I think you're confusing "in the common superclass of all virtio
> transports" vs "in the common superclass of all virtio devices".
> virtio.c only implements a common superclass of all virtio devices; in
> fact, there is no common superclass of all virtio transports, and it is
> not possible without multiple inheritance or stuff like traits (you're
> already inheriting from PCIDevice for virtio-*-pci).
> 
> Such common superclass, if it existed, would abstract stuff like "write
> zero to the status register" and would call qdev_reset_all.  But again,
> we don't have this concept.
> 
> Paolo

There's some misunderstanding here.

This is not about classes and stuff.

Common code should be in a single place so everyone can reuse it through
function calls, not duplicated in all transports.
And yes we do have examples of this if you are asking for examples;
examples are functions like virtio_reset, virtio_set_status, etc.


> > 
> > 
> >> ---
> >>  hw/virtio-pci.c | 28 ++++++++++------------------
> >>  1 file changed, 10 insertions(+), 18 deletions(-)
> >>
> >> diff --git a/hw/virtio-pci.c b/hw/virtio-pci.c
> >> index a7c75fe..2cf5282 100644
> >> --- a/hw/virtio-pci.c
> >> +++ b/hw/virtio-pci.c
> >> @@ -268,12 +268,10 @@ static void virtio_ioport_write(void *opaque, 
> >> uint32_t addr, uint32_t val)
> >>      case VIRTIO_PCI_QUEUE_PFN:
> >>          pa = (hwaddr)val << VIRTIO_PCI_QUEUE_ADDR_SHIFT;
> >>          if (pa == 0) {
> >> -            virtio_reset(proxy->vdev);
> >> -            virtio_pci_stop_ioeventfd(proxy);
> >> -            msix_unuse_all_vectors(&proxy->pci_dev);
> >> -        }
> >> -        else
> >> +            qdev_reset_all(&proxy->pci_dev.qdev);
> >> +        } else {
> >>              virtio_queue_set_addr(vdev, vdev->queue_sel, pa);
> >> +        }
> >>          break;
> >>      case VIRTIO_PCI_QUEUE_SEL:
> >>          if (val < VIRTIO_PCI_QUEUE_MAX)
> >> @@ -285,22 +283,16 @@ static void virtio_ioport_write(void *opaque, 
> >> uint32_t addr, uint32_t val)
> >>          }
> >>          break;
> >>      case VIRTIO_PCI_STATUS:
> >> -        if (vdev->status == 0) {
> >> -            virtio_reset(proxy->vdev);
> >> -        }
> >> -
> >> -        if (!(val & VIRTIO_CONFIG_S_DRIVER_OK)) {
> >> -            virtio_pci_stop_ioeventfd(proxy);
> >> -        }
> >> -
> >>          virtio_set_status(vdev, val & 0xFF);
> >>  
> >> -        if (val & VIRTIO_CONFIG_S_DRIVER_OK) {
> >> -            virtio_pci_start_ioeventfd(proxy);
> >> -        }
> >> -
> >>          if (vdev->status == 0) {
> >> -            msix_unuse_all_vectors(&proxy->pci_dev);
> >> +            qdev_reset_all(&proxy->pci_dev.qdev);
> >> +        } else {
> >> +            if (!(val & VIRTIO_CONFIG_S_DRIVER_OK)) {
> >> +                virtio_pci_stop_ioeventfd(proxy);
> >> +            } else {
> >> +                virtio_pci_start_ioeventfd(proxy);
> >> +            }
> >>          }
> >>  
> >>          /* Linux before 2.6.34 sets the device as OK without enabling
> >> -- 
> >> 1.8.0.2
> >>