Re: [Xen-devel] [PATCH v9 23/28] ARM: vITS: handle DISCARD command

[Julien Grall <julien.grall@xxxxxxx>]

On 22/05/17 17:50, Andre Przywara wrote:
> Hi,
Hi Andre,

> On 18/05/17 15:23, Julien Grall wrote:
> > Hi Andre,
> >
> > On 11/05/17 18:53, Andre Przywara wrote:
> > > The DISCARD command drops the connection between a DeviceID/EventID
> > > and an LPI/collection pair.
> > > We mark the respective structure entries as not allocated and make
> > > sure that any queued IRQs are removed.
> > >
> > > Signed-off-by: Andre Przywara <andre.przywara@xxxxxxx>
> > > ---
> > >  xen/arch/arm/vgic-v3-its.c | 24 ++++++++++++++++++++++++
> > >  1 file changed, 24 insertions(+)
> > >
> > > diff --git a/xen/arch/arm/vgic-v3-its.c b/xen/arch/arm/vgic-v3-its.c
> > > index ef7c78f..f7a8d77 100644
> > > --- a/xen/arch/arm/vgic-v3-its.c
> > > +++ b/xen/arch/arm/vgic-v3-its.c
> > > @@ -723,6 +723,27 @@ out_unlock:
> > >      return ret;
> > >  }
> > >
> > > +static int its_handle_discard(struct virt_its *its, uint64_t *cmdptr)
> > > +{
> > > +    uint32_t devid = its_cmd_get_deviceid(cmdptr);
> > > +    uint32_t eventid = its_cmd_get_id(cmdptr);
> > > +    int ret;
> > > +
> > > +    spin_lock(&its->its_lock);
> > > +
> > > +    /* Remove from the radix tree and remove the host entry. */
> > > +    ret = its_discard_event(its, devid, eventid);
> > > +
> > > +    /* Remove from the guest's ITTE. */
> > > +    if ( ret || write_itte_locked(its, devid, eventid,
> > > +                                  UNMAPPED_COLLECTION, INVALID_LPI,
> > > NULL) )
> > I am not sure to fully understand this if. If ret is not NULL you
> > override it and never call write_itte_locked.
> If its_discard_event() succeeded above, then ret will be 0, in which
> case we call write_itte_locked(). If that returns non-zero, this is an
> error and we set ret to -1, otherwise (no error) it stays at zero.
But we want to carry the error from its_discard_event. No?

Cheers,

--
Julien Grall

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