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Date: Tue, 16 May 2017 13:11:38 -0700 (PDT)
From: Stefano Stabellini <sstabellini@...nel.org>
To: Boris Ostrovsky <boris.ostrovsky@...cle.com>
cc: Stefano Stabellini <sstabellini@...nel.org>,
xen-devel@...ts.xen.org, linux-kernel@...r.kernel.org,
jgross@...e.com, Stefano Stabellini <stefano@...reto.com>
Subject: Re: [PATCH 04/18] xen/pvcalls: xenbus state handling
On Mon, 15 May 2017, Boris Ostrovsky wrote:
> On 05/15/2017 04:35 PM, Stefano Stabellini wrote:
> > Introduce the code to handle xenbus state changes.
> >
> > Implement the probe function for the pvcalls backend. Write the
> > supported versions, max-page-order and function-calls nodes to xenstore,
> > as required by the protocol.
> >
> > Introduce stub functions for disconnecting/connecting to a frontend.
> >
> > Signed-off-by: Stefano Stabellini <stefano@...reto.com>
> > CC: boris.ostrovsky@...cle.com
> > CC: jgross@...e.com
> > ---
> > drivers/xen/pvcalls-back.c | 133
> > +++++++++++++++++++++++++++++++++++++++++++++
> > 1 file changed, 133 insertions(+)
> >
> > diff --git a/drivers/xen/pvcalls-back.c b/drivers/xen/pvcalls-back.c
> > index 46a889a..86eca19 100644
> > --- a/drivers/xen/pvcalls-back.c
> > +++ b/drivers/xen/pvcalls-back.c
> > @@ -25,6 +25,9 @@
> > #include <xen/xenbus.h>
> > #include <xen/interface/io/pvcalls.h>
> >
> > +#define PVCALLS_VERSIONS "1"
> > +#define MAX_RING_ORDER XENBUS_MAX_RING_GRANT_ORDER
> > +
> > struct pvcalls_ioworker {
> > struct work_struct register_work;
> > atomic_t io;
> > @@ -45,15 +48,145 @@ static void pvcalls_back_ioworker(struct work_struct
> > *work)
> > {
> > }
> >
> > +static int backend_connect(struct xenbus_device *dev)
> > +{
> > + return 0;
> > +}
> > +
> > +static int backend_disconnect(struct xenbus_device *dev)
> > +{
> > + return 0;
> > +}
> > +
> > static int pvcalls_back_probe(struct xenbus_device *dev,
> > const struct xenbus_device_id *id)
> > {
> > + int err;
> > +
> > + err = xenbus_printf(XBT_NIL, dev->nodename, "versions", "%s",
> > + PVCALLS_VERSIONS);
> > + if (err) {
> > + pr_warn("%s write out 'version' failed\n", __func__);
> > + return -EINVAL;
>
> Why not return err? (below too)
Yeah, I'll make the change.
> > + }
> > +
> > + err = xenbus_printf(XBT_NIL, dev->nodename, "max-page-order", "%u",
> > + MAX_RING_ORDER);
> > + if (err) {
> > + pr_warn("%s write out 'max-page-order' failed\n", __func__);
> > + return -EINVAL;
> > + }
> > +
> > + /* "1" means socket, connect, release, bind, listen, accept and poll*/
> > + err = xenbus_printf(XBT_NIL, dev->nodename, "function-calls", "1");
>
>
> Should "1" be defined in the (public) header file?
Fair enough, it makes sense.
> > + if (err) {
> > + pr_warn("%s write out 'function-calls' failed\n", __func__);
> > + return -EINVAL;
> > + }
> > +
> > + err = xenbus_switch_state(dev, XenbusStateInitWait);
> > + if (err)
> > + return err;
> > +
> > return 0;
> > }
> >
> > +static void set_backend_state(struct xenbus_device *dev,
> > + enum xenbus_state state)
> > +{
> > + while (dev->state != state) {
> > + switch (dev->state) {
> > + case XenbusStateClosed:
> > + switch (state) {
> > + case XenbusStateInitWait:
> > + case XenbusStateConnected:
> > + xenbus_switch_state(dev, XenbusStateInitWait);
> > + break;
> > + case XenbusStateClosing:
> > + xenbus_switch_state(dev, XenbusStateClosing);
> > + break;
> > + default:
> > + __WARN();
> > + }
> > + break;
> > + case XenbusStateInitWait:
> > + case XenbusStateInitialised:
> > + switch (state) {
> > + case XenbusStateConnected:
> > + backend_connect(dev);
> > + xenbus_switch_state(dev,
> > XenbusStateConnected);
> > + break;
> > + case XenbusStateClosing:
> > + case XenbusStateClosed:
> > + xenbus_switch_state(dev, XenbusStateClosing);
> > + break;
> > + default:
> > + __WARN();
> > + }
> > + break;
> > + case XenbusStateConnected:
> > + switch (state) {
> > + case XenbusStateInitWait:
> > + case XenbusStateClosing:
> > + case XenbusStateClosed:
> > + down_write(&pvcalls_back_global.privs_lock);
> > + backend_disconnect(dev);
> > + up_write(&pvcalls_back_global.privs_lock);
>
>
> Unless you plan to have more stuff under the semaphore, I'd consider putting
> them in backend_disconnect().
Yes, there will be more things in pvcalls_back_fin (the function that
implements module_exit in patch #14).
> > + xenbus_switch_state(dev, XenbusStateClosing);
> > + break;
> > + default:
> > + __WARN();
> > + }
> > + break;
> > + case XenbusStateClosing:
> > + switch (state) {
> > + case XenbusStateInitWait:
> > + case XenbusStateConnected:
> > + case XenbusStateClosed:
> > + xenbus_switch_state(dev, XenbusStateClosed);
> > + break;
> > + default:
> > + __WARN();
> > + }
> > + break;
> > + default:
> > + __WARN();
> > + }
> > + }
> > +}
> > +
> > static void pvcalls_back_changed(struct xenbus_device *dev,
> > enum xenbus_state frontend_state)
> > {
> > + switch (frontend_state) {
> > + case XenbusStateInitialising:
> > + set_backend_state(dev, XenbusStateInitWait);
> > + break;
> > +
> > + case XenbusStateInitialised:
> > + case XenbusStateConnected:
> > + set_backend_state(dev, XenbusStateConnected);
> > + break;
> > +
> > + case XenbusStateClosing:
> > + set_backend_state(dev, XenbusStateClosing);
> > + break;
> > +
> > + case XenbusStateClosed:
> > + set_backend_state(dev, XenbusStateClosed);
> > + if (xenbus_dev_is_online(dev))
> > + break;
> > + /* fall through if not online */
> > + case XenbusStateUnknown:
> > + set_backend_state(dev, XenbusStateClosed);
>
>
> You are setting XenbusStateClosed twice in case of fallthrough.
I'll fix it.
> > + device_unregister(&dev->dev);
> > + break;
> > +
> > + default:
> > + xenbus_dev_fatal(dev, -EINVAL, "saw state %d at frontend",
> > + frontend_state);
> > + break;
> > + }
> > }
> >
> > static int pvcalls_back_remove(struct xenbus_device *dev)
> >
>
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