Re: [Xen-devel] [PATCH v3 3/3] tools: introduce parameter max_wp_ram_ranges.

["Yu, Zhang" <yu.c.zhang@xxxxxxxxxxxxxxx>]

On 2/2/2016 11:21 PM, Jan Beulich wrote:
> > > > On 02.02.16 at 16:00, <yu.c.zhang@xxxxxxxxxxxxxxx> wrote:
> > The limit of 4G is to avoid the data missing from uint64 to uint32
> > assignment. And I can accept the 8K limit for XenGT in practice.
> > After all, it is vGPU page tables we are trying to trap and emulate,
> > not normal page frames.
> >
> > And I guess the reason that one domain exhausting Xen's memory can
> > affect another domain is because rangeset uses Xen heap, instead of the
> > per-domain memory. So what about we use a 8K limit by now for XenGT,
> > and in the future, if a per-domain memory allocation solution for
> > rangeset is ready, we do need to limit the rangeset size. Does this
> > sounds more acceptable?
> The lower the limit the better (but no matter how low the limit
> it won't make this a pretty thing). Anyway I'd still like to wait
> for what Ian may further say on this.
Hi Jan, I just had a discussion with my colleague. We believe 8K could
be the biggest limit for the write-protected ram ranges. If in the
future, number of vGPU page tables exceeds this limit, we will modify
our back-end device model to find a trade-off method, instead of
extending this limit. If you can accept this value as the upper bound
of rangeset, maybe we do not need to add any tool stack parameters, but
define a MAX_NR_WR_RAM_RANGES for the write-protected ram rangesset. As
to other rangesets, we keep their limit as 256. Does this sounds OK? :)

B.R.
Yu


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