Re: [Qemu-devel] [PATCH 1/2] virtio-pci: reset all qbuses too when writing to the status field

[Michael S. Tsirkin]

On Wed, Dec 12, 2012 at 03:26:35PM +0100, Paolo Bonzini wrote:
> virtio-pci devices do not perform a full reset when zero is written
> to the status field.  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).
> 
> The patch calls qdev_reset_all, which calls virtio_pci_reset,
> instead of basically inlining the contents of the latter.
> 
> Reported-by: Bryan Venteicher <address@hidden>
> Cc: Michael S. Tsirkin <address@hidden>
> Signed-off-by: Paolo Bonzini <address@hidden>

This is a device specific register, IMO it should reset
very specific things not what happens to be on the bus.
For example qdev resets the PCI header: will or
will not this reset it? It should not but no easy way to figure out.

Can't the required code just go into the virtio-scsi
reset callback?

> ---
>  hw/virtio-pci.c | 25 ++++++++++---------------
>  1 file changed, 10 insertions(+), 15 deletions(-)
> 
> diff --git a/hw/virtio-pci.c b/hw/virtio-pci.c
> index 71f4fb5..a1685f1 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_pci_stop_ioeventfd(proxy);
> -            virtio_reset(proxy->vdev);
> -            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)
> @@ -285,19 +283,16 @@ static void virtio_ioport_write(void *opaque, uint32_t 
> addr, uint32_t val)
>          }
>          break;
>      case VIRTIO_PCI_STATUS:
> -        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) {
> -            virtio_reset(proxy->vdev);
> -            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
> -- 
> 1.8.0.1
>