Re: [Qemu-devel] Re: [PATCH 2 of 5] add can_dma/post_dma for direct IO

[Jamie Lokier]

Anthony Liguori wrote:
> Let me clarify this a bit more.  The problem we're trying to address 
> today is the encapsulating knowledge of phys_ram_base.  We want to 
> minimize the amount of code that makes any assumptions about 
> phys_ram_base.  Your current API still accesses phys_ram_base directly 
> in the PCI DMA API.  The only real improvement compared to the current 
> virtio code is that you properly handle MMIO.  This is not just about 
> layout but this also includes the fact that in the future, guest memory 
> could be discontiguous in QEMU (think memory hotplug).

One little extra thing:

What about PCI DMA to another PCI device, not to RAM?

That's not used very often, but it ought to work.

-- Jamie