Re: [Qemu-devel] [PULL 16/53] virtio-pci: call pci reset variant when guest requests reset.

[Laszlo Ersek <lersek@redhat.com>]

On 03/11/16 16:08, Michael S. Tsirkin wrote:
> From: Gerd Hoffmann <kraxel@redhat.com>
> 
> Actually fixes linux not finding virtio 1.0 device virtqueues after
> reboot.  Which is new I think, any chance linux kernel virtio code
> became more strict in 4.3?
> 
> Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
> Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> Reviewed-by: Fam Zheng <famz@redhat.com>
> Tested-by: Fam Zheng <famz@redhat.com>
> ---
>  hw/virtio/virtio-pci.c | 11 ++++-------
>  1 file changed, 4 insertions(+), 7 deletions(-)
> 
> diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
> index 440776c..0dadb66 100644
> --- a/hw/virtio/virtio-pci.c
> +++ b/hw/virtio/virtio-pci.c
> @@ -47,6 +47,7 @@
>  
>  static void virtio_pci_bus_new(VirtioBusState *bus, size_t bus_size,
>                                 VirtIOPCIProxy *dev);
> +static void virtio_pci_reset(DeviceState *qdev);
>  
>  /* virtio device */
>  /* DeviceState to VirtIOPCIProxy. For use off data-path. TODO: use QOM. */
> @@ -404,9 +405,7 @@ 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(vdev);
> -            msix_unuse_all_vectors(&proxy->pci_dev);
> +            virtio_pci_reset(DEVICE(proxy));
>          }
>          else
>              virtio_queue_set_addr(vdev, vdev->queue_sel, pa);
> @@ -432,8 +431,7 @@ static void virtio_ioport_write(void *opaque, uint32_t addr, uint32_t val)
>          }
>  
>          if (vdev->status == 0) {
> -            virtio_reset(vdev);
> -            msix_unuse_all_vectors(&proxy->pci_dev);
> +            virtio_pci_reset(DEVICE(proxy));
>          }
>  
>          /* Linux before 2.6.34 drives the device without enabling
> @@ -1353,8 +1351,7 @@ static void virtio_pci_common_write(void *opaque, hwaddr addr,
>          }
>  
>          if (vdev->status == 0) {
> -            virtio_reset(vdev);
> -            msix_unuse_all_vectors(&proxy->pci_dev);
> +            virtio_pci_reset(DEVICE(proxy));
>          }
>  
>          break;
> 

I spent about two days hunting this, and was just about to send a patch.
Nice to see you've already gotten to it. :)

The specific problem was that the queue_enable field was not cleared
(for all possible queues of the device) on device reset, only on system
reset.

Thanks
Laszlo