Re: [Xen-devel] [PATCH v10 1/6] x86: detect and initialize Cache QoS Monitoring feature

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 03.04.14 at 10:27, <dongxiao.xu@xxxxxxxxx> wrote:
>> From: xen-devel-bounces@xxxxxxxxxxxxx 
>> [mailto:xen-devel-bounces@xxxxxxxxxxxxx] On Behalf Of Jan Beulich
>> But you could get away with a split approach: Provide the socket ID
>> list via ordinary hypercall means (if this isn't already derivable from
>> the topology sysctl anyway), and only share the per-socket data
>> page(s).
> 
> sysctl->u.getcqminfo has size limitation of 128 bytes.
> The per-socket MFN array _may_ exceed this limitation...
> 
> We discussed this issue in previous threads, that's how this 2-level of 
> data_mfn/data page sharing mechanism is proposed.

That's unrelated - you can always introduce a handle pointing to the
array where the MFNs are to be stored. Whether that's preferable
over the shared page approach largely depends on the number of
entries in the page, and the performance needs. Both I think would
suggest to use the handle-to-array approach, and use shared pages
only for the actual data.

Jan


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