Re: [Xen-devel] [PATCH 3/5] xen: virq, remove VIRQ_XC_RESERVED

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 06.08.12 at 17:13, Ian Campbell <Ian.Campbell@xxxxxxxxxx> wrote:
> On Mon, 2012-08-06 at 16:01 +0100, Jean Guyader wrote:
>> On 6 August 2012 15:56, Ian Campbell <Ian.Campbell@xxxxxxxxxx> wrote:
>> > On Mon, 2012-08-06 at 15:46 +0100, Jean Guyader wrote:
>> >> On 6 August 2012 09:10, Jan Beulich <JBeulich@xxxxxxxx> wrote:
>> >> >>>> On 03.08.12 at 21:50, Jean Guyader <jean.guyader@xxxxxxxxxx> wrote:
>> >> >> VIRQ_XC_RESERVED was reserved for V4V but we have switched
>> >> >> to event channels so this place holder is no longer required.
>> >> >
>> >> > I'm fine with this change, but is a future re-use of the value indeed
>> >> > not going to cause problems on XenServer (or wherever else this
>> >> > is patch set coming from)?
>> >> >
>> >>
>> >> That may need to be confirmed but I don't think XenServer is using v4v
>> >> yet
>> >
>> > I think Jan probably meant XenClient (i.e. that being the place where
>> > v4v is already deployed).
>> >
>> > There's no harm in keeping this # reserved indefinitely, with a suitable
>> > comment, I think? The only reason not to would be if this address space
>> > was limited, but I don't think that is the case with VIRQs
>> >
>> >
>> 
>> I think if XenClient rebase to a new version of Xen we will probably
>> use the version of
>> v4v that comes with it and we will not try to rebase the old code on
>> the newer Xen.
> 
> I think Jan's concern was if a current client runs on some future
> version of Xen which has reused that VIRQ for something else, some sort
> of weirdness would probably ensue?

That was exactly the point of my inquiry.

Jan


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