Re: [Xen-devel] [PATCH] IRQ: u16 is too narrow for an event channel number

[Julien Grall <julien@xxxxxxx>]

Hi Jan,

On 14/01/2020 10:23, Jan Beulich wrote:
> On 14.01.2020 11:16, Julien Grall wrote:
> > Hi Jan,
> >
> > On 14/01/2020 10:02, Jan Beulich wrote:
> > > FIFO event channels allow ports up to 2^17, so we need to use a wider
> > > field in struct pirq. Move "masked" such that it may share the 8-byte
> > > slot with struct arch_pirq on 64-bit arches, rather than leaving a
> > > 7-byte hole in all cases.
> > >
> > > Take the opportunity and also add a comment regarding "arch" placement
> > > within the structure.
> > >
> > > Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> > >
> > > --- a/xen/include/xen/irq.h
> > > +++ b/xen/include/xen/irq.h
> > > @@ -127,9 +127,10 @@ struct vcpu;
> > >    
> > >    struct pirq {
> > >        int pirq;
> > > -    u16 evtchn;
> > > -    bool_t masked;
> > > +    evtchn_port_t evtchn;
> > >        struct rcu_head rcu_head;
> > > +    bool masked;
> > > +    /* Architectures may require this field to be last. */
> > I orginally planned to add a comment in struct pirq, but I am not in
> > favor to continue to encourage quirkiness in the code. I sent a series
> > (see [1]) that drop this requirements from x86 and therefore remove the
> > need of this comment.
> Well, I've found the issue fixed here while doing a first review pass
> over said patch of yours (I'm yet to make up my mind whether I have
> reservations, hence I didn't reply yet). The change here will want
> backporting, so it'll be easier in any event to rebase your patch over
> this one. This rebasing can then include dropping the comment again.
Fair enough.

Cheers,

--
Julien Grall

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