* Will Deacon <[email protected]> [2020-04-30 11:14:32]:
> > +#ifdef CONFIG_VIRTIO_MMIO_OPS
> >
> > +static struct virtio_mmio_ops *mmio_ops;
> > +
> > +#define virtio_readb(a) mmio_ops->mmio_readl((a))
> > +#define virtio_readw(a) mmio_ops->mmio_readl((a))
> > +#define virtio_readl(a) mmio_ops->mmio_readl((a))
> > +#define virtio_writeb(val, a) mmio_ops->mmio_writeb((val), (a))
> > +#define virtio_writew(val, a) mmio_ops->mmio_writew((val), (a))
> > +#define virtio_writel(val, a) mmio_ops->mmio_writel((val), (a))
>
> How exactly are these ops hooked up? I'm envisaging something like:
>
> ops = spec_compliant_ops;
> [...]
> if (firmware_says_hypervisor_is_buggy())
> ops = magic_qcom_ops;
>
> am I wrong?
If CONFIG_VIRTIO_MMIO_OPS is defined, then I expect this to be unconditionally
set to 'magic_qcom_ops' that uses hypervisor-supported interface for IO (for
example: message_queue_send() and message_queue_recevie() hypercalls).
> > +int register_virtio_mmio_ops(struct virtio_mmio_ops *ops)
> > +{
> > + pr_info("Registered %s as mmio ops\n", ops->name);
> > + mmio_ops = ops;
>
> Not looking good, and really defeats the point of standardising this stuff
> imo.
Ok. I guess the other option is to standardize on a new virtio transport (like
ivshmem2-virtio)?
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