Re: [Xen-ia64-devel] [patch] calculate dom0 metaphysical load address correctly

[Isaku Yamahata <yamahata@xxxxxxxxxxxxx>]

On Thu, May 24, 2007 at 12:28:46PM +0200, Jes Sorensen wrote:
> Isaku Yamahata wrote:
> > On Thu, May 24, 2007 at 11:38:19AM +0200, Jes Sorensen wrote:
> > P=M will break the current grant table api. It means all of virtual
> > io device (balloon, vbd, vnif, ...) will be broken.
> > What do you think about it?
> 
> Then we have to fix it - the Linux kernel requires this, it's not
> optional. Sure it works for over simplified systems such as DIG, but
> anything moderately advanced will break.

I don't agree here.
I think fixing it with P=M requires much bigger efforts than
paravirtualizing the files under sn/ directory.
Looking around sn/ directory, I found that address conversion
functions are centralized in linux/include/asm-ia64/sn/addr.h.
It has only 295 lines. I don't think it's unrealistic to
paravirtualize them.


> > In fact, Virtual Physical address model was introduced to
> > resolve the grant table issue. And the ia64 default dma api and
> > hp zx1 iommu are already paravirtulized.
> 
> There's much more to it than that. We need it for things like
> alloc_pages_node() in the Linux kernel if we want any level of
> performance.

I'm talking about dma api paravirtualization, not NUMA.
I believe that it's feasible to support NUMA without P=M.


> I mean if we want to let individual dom's have direct access to a PCI
> device. They will need to know where in the system it's physically
> located.

It is already supported.

-- 
yamahata

_______________________________________________
Xen-ia64-devel mailing list
Xen-ia64-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-ia64-devel