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xen-devel
Re: [Xen-devel] Essay on an important Xen decision (long)
Le Mardi 10 Janvier 2006 20:55, Anthony Liguori a écrit :
> Hi Dan,
>
> Thanks for the thorough explaination of physical memory virtualization.
> It's a topic that there isn't a lot of good reference on.
>
> You seem to conclude that the only possible solutions are making the
> dom0 either P==M or P2M. Is it not possible to make dom0 VP?
>
> If the only issue for making dom0 VP is DMA, wouldn't it be easier to
> modify the Linux DMA subsystem[1] to make a special hypercall to
> essentially pin a VP to a particular MFN that could be used for the
> DMA? One could imagine the hypervisor reversing low memory specifically
> for DMA such that bounce buffers could be avoided too.
>
> VP makes a lot of interesting memory optimizations considerably easier
> (memory compacting, swapping, etc.).
>
> [1] Realizing that I know very little about the Linux DMA subsystem so I
> don't know if this is outside the realm of possibilities.
Hi,
a few years ago (it was with linux 2.2), I wrote device drivers for rather
complex hardware. DMA subsystem didn't really exist. The main reason is an
hardware reason: DMA chip do not exist anymore because nowaday (almost since
PCI) every driver chip do DMA by itself.
Tristan.
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