Re: [PATCH v2 10/23] xen/arm: compile and run xenbus

Stefano Stabellini
2012-08-08T16:52:07Z

On Tue, 7 Aug 2012, Daniel De Graaf wrote:
> On 08/07/2012 02:21 PM, Konrad Rzeszutek Wilk wrote:
> > On Mon, Aug 06, 2012 at 03:27:13PM +0100, Stefano Stabellini wrote:
> >> bind_evtchn_to_irqhandler can legitimately return 0 (irq 0): it is not
> >> an error.
> >>
> >> If Linux is running as an HVM domain and is running as Dom0, use
> >> xenstored_local_init to initialize the xenstore page and event channel.
> >>
> >> Changes in v2:
> >>
> >> - refactor xenbus_init.
> >
> > Thank you. Lets also CC our friend at NSA who has been doing some work
> > in that area. Daniel are you OK with this change - will it still make
> > PV initial domain with with the MiniOS XenBus driver?
> >
> > Thanks.
>
> That case will work, but what this will break is launching the initial domain
> with a Xenstore stub domain already running (see below).
>
> >>
> >> Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
> >> ---
> >> drivers/xen/xenbus/xenbus_comms.c | 2 +-
> >> drivers/xen/xenbus/xenbus_probe.c | 62 +++++++++++++++++++++++++-----------
> >> drivers/xen/xenbus/xenbus_xs.c | 1 +
> >> 3 files changed, 45 insertions(+), 20 deletions(-)
> >>
> >> diff --git a/drivers/xen/xenbus/xenbus_comms.c b/drivers/xen/xenbus/xenbus_comms.c
> >> index 52fe7ad..c5aa55c 100644
> >> --- a/drivers/xen/xenbus/xenbus_comms.c
> >> +++ b/drivers/xen/xenbus/xenbus_comms.c
> >> @@ -224,7 +224,7 @@ int xb_init_comms(void)
> >> int err;
> >> err = bind_evtchn_to_irqhandler(xen_store_evtchn, wake_waiting,
> >> 0, "xenbus", &xb_waitq);
> >> - if (err <= 0) {
> >> + if (err < 0) {
> >> printk(KERN_ERR "XENBUS request irq failed %i\n", err);
> >> return err;
> >> }
> >
> >> diff --git a/drivers/xen/xenbus/xenbus_probe.c b/drivers/xen/xenbus/xenbus_probe.c
> >> index b793723..a67ccc0 100644
> >> --- a/drivers/xen/xenbus/xenbus_probe.c
> >> +++ b/drivers/xen/xenbus/xenbus_probe.c
> >> @@ -719,37 +719,61 @@ static int __init xenstored_local_init(void)
> >> return err;
> >> }
> >>
> >> +enum xenstore_init {
> >> + UNKNOWN,
> >> + PV,
> >> + HVM,
> >> + LOCAL,
> >> +};
> >> static int __init xenbus_init(void)
> >> {
> >> int err = 0;
> >> + enum xenstore_init usage = UNKNOWN;
> >> + uint64_t v = 0;
> >>
> >> if (!xen_domain())
> >> return -ENODEV;
> >>
> >> xenbus_ring_ops_init();
> >>
> >> - if (xen_hvm_domain()) {
> >> - uint64_t v = 0;
> >> - err = hvm_get_parameter(HVM_PARAM_STORE_EVTCHN, &v);
> >> - if (err)
> >> - goto out_error;
> >> - xen_store_evtchn = (int)v;
> >> - err = hvm_get_parameter(HVM_PARAM_STORE_PFN, &v);
> >> - if (err)
> >> - goto out_error;
> >> - xen_store_mfn = (unsigned long)v;
> >> - xen_store_interface = ioremap(xen_store_mfn << PAGE_SHIFT, PAGE_SIZE);
> >> - } else {
> >> - xen_store_evtchn = xen_start_info->store_evtchn;
> >> - xen_store_mfn = xen_start_info->store_mfn;
> >> - if (xen_store_evtchn)
> >> - xenstored_ready = 1;
> >> - else {
> >> + if (xen_pv_domain())
> >> + usage = PV;
> >> + if (xen_hvm_domain())
> >> + usage = HVM;
>
> The above is correct for domUs, and is overridden for dom0s:
>
> >> + if (xen_hvm_domain() && xen_initial_domain())
> >> + usage = LOCAL;
> >> + if (xen_pv_domain() && !xen_start_info->store_evtchn)
> >> + usage = LOCAL;
>
> Instead of these checks, I think it should just be:
>
> if (!xen_start_info->store_evtchn)
> usage = LOCAL;
>
> Any domain started after xenstore will have store_evtchn set, so if you don't
> have this set, you are either going to be running xenstore locally, or will
> use the ioctl to change it later (and so should still set up everything as if
> it will be running locally).

That would be wrong for an HVM dom0 domain (at least on ARM), because
we don't have a start_info page at all.

> >> + if (xen_pv_domain() && xen_start_info->store_evtchn)
> >> + xenstored_ready = 1;
>
> This part can now just be moved unconditionally into case PV.

What about:

if (xen_pv_domain())
usage = PV;
if (xen_hvm_domain())
usage = HVM;
if (!xen_store_evtchn)
usage = LOCAL;

and moving xenstored_ready in case PV, like you suggested.