Re: [Xen-devel] [PATCH v3 13/24] xen/arm: Implement hypercall PHYSDEVOP_{, un}map_pirq

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Thu, 29 Jan 2015, Julien Grall wrote:
> On 29/01/15 12:17, Stefano Stabellini wrote:
> > On Wed, 28 Jan 2015, Julien Grall wrote:
> >> Hi Stefano,
> >>
> >> On 28/01/15 18:52, Stefano Stabellini wrote:
> >>> On Tue, 13 Jan 2015, Julien Grall wrote:
> >>>> The physdev sub-hypercalls PHYSDEVOP_{,map}_pirq allow the toolstack to
> >>>> assign/deassign a physical IRQ to the guest (via the config options 
> >>>> "irqs"
> >>>> for xl). The x86 version is using them with PIRQ (IRQ bound to an event
> >>>> channel). As ARM doesn't have a such concept, we could reuse it to bound
> >>>> a physical IRQ to a virtual IRQ.
> >>>>
> >>>> For now, we allow only SPIs to be mapped to the guest.
> >>>> The type MAP_PIRQ_TYPE_GSI is used for this purpose.
> >>>>
> >>>> Signed-off-by: Julien Grall <julien.grall@xxxxxxxxxx>
> >>>> Cc: Jan Beulich <jbeulich@xxxxxxxx>
> >>>>
> >>>> ---
> >>>>     I'm not sure it's the best solution to reuse hypercalls for a
> >>>>     different purpose. If x86 plan to have a such concept (i.e binding a
> >>>>     physical IRQ to a virtual IRQ), we could introduce new hypercalls.
> >>>>     Any thoughs?
> >>>
> >>> I think it is OK, as long as we write down very clearly what we are
> >>> doing.
> >>>
> >>>
> >>>>     TODO: This patch is lacking of support of vIRQ != IRQ. I plan to
> >>>>     handle it correctly on the next version.
> >>>
> >>> Why do you say that? From the code in this patch it looks like it
> >>> supports vIRQ != IRQ already.
> >>
> >> Because PHYSDEV_map_pirq is taking a vIRQ number in parameter. This vIRQ
> >> is only valid for the domain which issue the hypercall.
> > 
> > That's not very useful. I think that the vIRQ passed to PHYSDEV_map_pirq
> > should be a vIRQ in the destination domain, not the source domain.
> > 
> > In fact on x86 the pirq parameter to PHYSDEV_map_pirq is interpreted as
> > pirq in the destination domain too.
> 
> I'm talking about the index parameter. It's a vIRQ in the domain issue
> the hypercall not the real IRQ.

I see.  OK.


> >> In our use case, it's DOM0. DOM0 may not have all the time vIRQ == IRQ.
> >>
> >> Futhermore, on PHYSDEV_unmap_pirq I assume the DOM0 virq == guest virq.
> > 
> > That's bad.
> 
> I plan to support it for the next series. This change shouldn't impact
> the other patches of the series, so I decided to send a new version to
> gather some comments.
> 
> Regards,
> 
> -- 
> Julien Grall
> 

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel