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Re: [Xen-devel] [PATCH 18/22] vixen: Introduce ECS_PROXY for event channel proxying

On 01/07/2018 04:46 PM, Anthony Liguori wrote:
> On Sun, Jan 7, 2018 at 12:44 AM, Roger Pau Monné <roger.pau@xxxxxxxxxx> wrote:
>> On Sat, Jan 06, 2018 at 02:54:33PM -0800, Anthony Liguori wrote:
>>> From: Jan H. Schönherr <jschoenh@xxxxxxxxx>
>>> Previously, we would keep proxied event channels as ECS_INTERDOMAIN
>>> channel around. This works for most things, but has the problem
>>> that EVTCHNOP_status is broken, and that EVTCHNOP_close does not
>>> mark an event channel as free.
>> Why not use ECS_RESERVED for event channels that are forwarded to L0?
>> You could easily see whether an event channel is forwarded or not just
>> by checking if it's ECS_RESERVED, and then decide whether to forward
>> the hypercall to L0 or handle it in vixen.
> Jan?

I didn't go for RESERVED, because of potential confusion with other RESERVED
ports. AFAIK, there's only port 0 that's reserved, currently. If you don't
want to distinguish between "reserved" and "proxied", you'd have to forward
operations on port 0 as well, and then rely on port 0 being reserved in L0
as well.

Using a separate ECS_PROXY seemed cleaner to me. Less chance to get it wrong
or for it to accidentally get broken by a future change. :)


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