[Qemu-devel] virtio_mmio address mapping

[Qemu-devel] virtio_mmio address mapping

[Dean]

hi,all,

I am writing a UIO linux driver for a virtio_mmio device and find out that all those virtio_mmio devices' registers are arrange in one single 4K aligned page.
which makes writing an UIO driver hard since linux doesn't allow UIO driver to map a register space smaller than page size.
would you consider divide them into defferent pages?

what I am talking about is devices like:
a003000.virtio_mmio
a003c00.virtio_mmio
a003e00.virtio_mmio

what I am dealing with is a003e00.virtio_mmio

Dean

Re: [Qemu-devel] virtio_mmio address mapping

[Peter Maydell]

On 30 May 2016 at 13:24, Dean <664543912@qq.com> wrote:
> I am writing a UIO linux driver for a virtio_mmio device and find out that all those virtio_mmio devices' registers are arrange in one single 4K aligned page.
> which makes writing an UIO driver hard since linux doesn't allow UIO driver to map a register space smaller than page size.
> would you consider divide them into defferent pages?
>
> what I am talking about is devices like:
> a003000.virtio_mmio
> a003c00.virtio_mmio
> a003e00.virtio_mmio
>
> what I am dealing with is a003e00.virtio_mmio

Unfortunately we can't really move them, for backwards
compatibility reasons. Also, virtio-mmio is now pretty
much obsolete since you can use virtio-pci instead, and
we wouldn't want it to take up much more of the physical
address space.

thanks
-- PMM