[Qemu-devel] Re: [PATCH 0/2] fix virtio_blk serial pci config breakage

["Michael S. Tsirkin" <mst@redhat.com>]

On Tue, Sep 29, 2009 at 02:09:30AM -0400, john cooper wrote:
> This is a correction to the previous version
> which violated the PCI config space 256 byte
> limitation.
> 
> The crux of the feature is simply passing a qemu
> received virtio serial number to/through the guest
> driver and making it available to guest userspace
> via a preexisting interface.
> 
> To accomplish this, ATA IDENTIFY data as implemented
> by the HDIO_GET_IDENTITY ioctl is returned to the
> caller for the virtio_blk drive of interest.  Content
> of this identify structure is created by qemu and
> passed wholesale to guest userspace without
> interpretation by the guest driver.
> 
> The change this patch implements is passing of the
> identify data through a mapping established by
> PCI BAR #5 rather than the PCI config area, the
> latter of which resulted in the above breakage.

Using bar per feature we'll quickly run out of BARs.
We already use a BAR for MSI-X - let's add
ATA identity there?

> virtio_blk with this patch now pulls the information
> from the mapped bar area and includes minimal
> scaffolding to help map bars external to virtio_pci.
> 
> -john
> 
> 
> -- 
> john.cooper@redhat.com