On Wed, 2011-11-23 at 10:49 +0200, Michael S. Tsirkin wrote:
> On Wed, Nov 23, 2011 at 01:02:22PM +1030, Rusty Russell wrote:
> > +/* Fields in VIRTIO_PCI_CAP_COMMON_CFG: */
> > +struct virtio_pci_common_cfg {
> > + /* About the whole device. */
> > + __u64 device_features; /* read-only */
> > + __u64 guest_features; /* read-write */
>
> We currently require atomic accesses to common fields.
> Some architectures might not have such for 64 bit,
> so these need to be split I think ...
We can consider stealing the feature implementation from virtio-mmio:
Use the first 32 bits as a selector and the last as the features
themselves.
It's more complex to work with, but it provides 2**32 32 feature bits
(which should be enough for a while) and it solves the atomic access
issue.
> > + __u64 queue_address; /* read-write */
> > + __u16 msix_config; /* read-write */
> > + __u8 device_status; /* read-write */
> > + __u8 unused;
> > +
> > + /* About a specific virtqueue. */
> > + __u16 queue_select; /* read-write */
> > + __u16 queue_align; /* read-write, power of 2. */
> > + __u16 queue_size; /* read-write, power of 2. */
> > + __u16 queue_msix_vector;/* read-write */
> > +};
> > #endif
> >
> >
--
Sasha.
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