Re: [PATCH 1/1] direct mmio for passthrough - kernel part

Andrea Arcangeli
2008-04-01T18:18:19Z

On Tue, Apr 01, 2008 at 10:20:49AM -0500, Anthony Liguori wrote:
> Which is apparently entirely unnecessary as we already have
> /sys/bus/pci/.../region. It's just a matter of checking if a vma is VM_IO
> and then dealing with the subsequent reference counting issues as Avi
> points out.

Do you need to map it in userland too, isn't it enough to map it in
the sptes?

For the ram I had to map it in userland too with /dev/mem, and then I
used the pte_pfn to fill the spte, so the emulated qemu drivers can
input/output. But for the mmio space I doubt the userland side is
needed.

If you add a direct memslot (new bitflag type) I will use it too
instead of catching get_user_pages failures and walking ptes on the
RAM pieces overwritten by /dev/mem.