Re: [Xen-devel] grant table size

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Wed, Nov 20, 2019 at 09:43:59AM +0000, Durrant, Paul wrote:
> I've dealt with a few problems over the years where the root cause was a 
> guest running out of grant table and so I'm wondering whether it would be a 
> good idea to allow a toolstack to increase the table size of a running guest, 
> e.g. when plugging in a new PV interface.
I would rather have a new xl command that does the grant table
increase (ie: xl set-max-grant-frames) instead of doing it when
plugging new interfaces.

> It would appear that current Linux guests would not be able to make use of 
> this as it stands (but that could be fixed), but as far as I can tell a pvops 
> kernel would not misbehave if the maximum table size were to increase. 
> Similarly Windows PV drivers would need modification to make use of a dynamic 
> maximum table size but would not misbehave as is.
> Does anyone have any objection to the idea?

Do you have in mind to signal this somehow to guests, or the
expectation is that the guest will have to poll GNTTABOP_query_size
and at some point the size will increase?

Thanks, Roger.

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