Re: [PATCH v3 for Xen 4.6 2/4] libxc: enable per-VCPU parameter settings for RTDS scheduler

[Ian Campbell <ian.campbell@citrix.com>]

On Tue, 2015-06-30 at 10:18 -0500, Chong Li wrote:
> On Tue, Jun 30, 2015 at 7:22 AM, Ian Campbell <ian.campbell@citrix.com> wrote:
> > On Sun, 2015-06-28 at 21:44 -0500, Chong Li wrote:
> >> Add xc_sched_rtds_vcpu_get/set functions to interact with Xen to get/set a domain's
> >> per-VCPU parameters.
> >>
> >> Changes on PATCH v2:
> >>
> >> 1) Minor modifications due to the change of struct xen_domctl_scheduler_op.
> >
> > This intra-version changelog should go after the -- so it doesn't appear
> > in the final commit message.
> 
> Ok, I see.
> >
> >> diff --git a/tools/libxc/xc_csched.c b/tools/libxc/xc_csched.c
> >> index 390c645..5a2bdf4 100644
> >> --- a/tools/libxc/xc_csched.c
> >> +++ b/tools/libxc/xc_csched.c
> >> @@ -36,7 +36,7 @@ xc_sched_credit_domain_set(
> >>      domctl.domain = (domid_t) domid;
> >>      domctl.u.scheduler_op.sched_id = XEN_SCHEDULER_CREDIT;
> >>      domctl.u.scheduler_op.cmd = XEN_DOMCTL_SCHEDOP_putinfo;
> >> -    domctl.u.scheduler_op.u.credit = *sdom;
> >> +    domctl.u.scheduler_op.u.d.credit = *sdom;
> >
> > I don't see any change to any types in this series, which makes me
> > suspect it is in another patch and that bisectability is therefore not
> > maintained through the series. Each patch in the series needs to build
> > when they are applied one by one.
> >
> > This probably means that at to at least some degree hypercall interface
> > changes need to be done in the same time as the libxc adjustments. You
> > can still keep the _new_ functionality in a separate patch of course (if
> > that makes sense in this case).
> 
> Because both per-domain and per-vcpu parameters are now unioned in
> struct xen_domctl_scheduler_op, we need to specify per-domain or
> per-vcpu when using domctl.u.scheduler_op.u (.d means per-domain, .v
> means per-vcpu). This change also happens to the XEN_DOMCTL_SCHEDOP_*
> handlers (of all schedulers), where the domctl.u.scheduler_op.u.* is
> passed to.

I understand the interface change, but the problem is that the interface
change and the change ot the users of that interface seem to be in
different patches, which breaks bisectability.

Does this series compile and work at every step?

i.e. the following combinations of patches from this 4 patch series all
need to build and work successfully:

Patch #1
Patch #1+#2
Patch #1+#2+#3
Patch #1+#2+#3+#4

Is that the case?

Ian.