Re: [Qemu-devel] [PATCH V2 0/5] hw/pvrdma: PVRDMA device implementation

[Marcel Apfelbaum]

On 21/12/2017 16:22, Michael S. Tsirkin wrote:
> On Thu, Dec 21, 2017 at 09:27:51AM +0200, Yuval Shaia wrote:
> > > > > What happens if guest attempts to register all its memory?
> > > >
> > > > Then we loose, is not different from bare metal, reg_mr will pin all the RAM.
> > >
> > > We need to find a way to communicate to guests about amount
> > > of memory they can pin.
> >
> > dev_caps.max_mr_size is the way device limits guest driver.
> > This value is controlled by the command line argument dev-caps-max-mr-size
> > so we should be fine (btw, default value is 1<<32).
>
> Isn't that still leaving the option for guest to register all memory,
> just in chunks?

We also have a parameter limiting the number of mrs (dev-caps-max-mr),
together with dev-caps-max-mr-size we can limit the memory the guests can pin.

Thanks,
Marcel

> > > > However this is only one scenario, and hopefully not much used
> > > > for RoCE. (I know IPoIB does that, but it doesn't make sense to use it with 
> > > > RoCE).
> > >
> > > SRP does it too AFAIK.