Re: [Xen-devel] [PATCH] Persistent grant maps for xen blk drivers

From: Konrad Rzeszutek Wilk
Date: Fri Sep 21 2012 - 13:24:26 EST


On Fri, Sep 21, 2012 at 05:17:36PM +0100, David Vrabel wrote:
> On 21/09/12 15:27, Konrad Rzeszutek Wilk wrote:
> > On Fri, Sep 21, 2012 at 01:23:48PM +0100, David Vrabel wrote:
> >>
> >> It's not just virtual space. blkback in pvops kernels allocates its
> >> pages from the balloon and if there aren't enough ballooned out pages it
> >> has to allocate real pages (releasing the MFN back to Xen).
> >>
> >> Classic kernels didn't need to do this as there was an API for allocate
> >> new "empty" struct page's that get mapped into kernel space.
> >
> > Can we ressurect/implement that in the new pvops? We could use the memory
> > hotplug mechanism to allocate "non-existent" memory.
>
> I don't see why not. Provided the limitations are documented I wouldn't
> make merging the persistent grant stuff dependent on it.

I was thinking about this in the future and not delay this [persistent grants].
>
> David
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