| Message ID | 20190823101534.465-2-anthony.perard@citrix.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2,1/2] xen-bus: Fix backend state transition on device reset | expand |
> -----Original Message----- > From: Anthony PERARD <anthony.perard@citrix.com> > Sent: 23 August 2019 11:16 > To: qemu-devel@nongnu.org > Cc: Anthony Perard <anthony.perard@citrix.com>; qemu-stable@nongnu.org; Stefano Stabellini > <sstabellini@kernel.org>; Paul Durrant <Paul.Durrant@citrix.com>; xen-devel@lists.xenproject.org > Subject: [PATCH v2 1/2] xen-bus: Fix backend state transition on device reset > > When a frontend wants to reset its state and the backend one, it > starts with setting "Closing", then waits for the backend (QEMU) to do > the same. > > But when QEMU is setting "Closing" to its state, it triggers an event > (xenstore watch) that re-execute xen_device_backend_changed() and set > the backend state to "Closed". QEMU should wait for the frontend to > set "Closed" before doing the same. > > Before setting "Closed" to the backend_state, we are also going to > check if there is a frontend. If that the case, when the backend state > is set to "Closing" the frontend should react and sets its state to > "Closing" then "Closed". The backend should wait for that to happen. > > Fixes: b6af8926fb858c4f1426e5acb2cfc1f0580ec98a > Signed-off-by: Anthony PERARD <anthony.perard@citrix.com> Reviewed-by: Paul Durrant <paul.durrant@citrix.com> > --- > Cc: qemu-stable@nongnu.org > --- > > Notes: > v2: > - use a helper > - Add InitWait and Initialised to the list of active state > > hw/xen/xen-bus.c | 23 ++++++++++++++++++++--- > 1 file changed, 20 insertions(+), 3 deletions(-) > > diff --git a/hw/xen/xen-bus.c b/hw/xen/xen-bus.c > index e40500242d..62c127b926 100644 > --- a/hw/xen/xen-bus.c > +++ b/hw/xen/xen-bus.c > @@ -516,6 +516,23 @@ static void xen_device_backend_set_online(XenDevice *xendev, bool online) > xen_device_backend_printf(xendev, "online", "%u", online); > } > > +/* > + * Tell from the state whether the frontend is likely alive, > + * i.e. it will react to a change of state of the backend. > + */ > +static bool xen_device_state_is_active(enum xenbus_state state) > +{ > + switch (state) { > + case XenbusStateInitWait: > + case XenbusStateInitialised: > + case XenbusStateConnected: > + case XenbusStateClosing: > + return true; > + default: > + return false; > + } > +} > + > static void xen_device_backend_changed(void *opaque) > { > XenDevice *xendev = opaque; > @@ -539,11 +556,11 @@ static void xen_device_backend_changed(void *opaque) > > /* > * If the toolstack (or unplug request callback) has set the backend > - * state to Closing, but there is no active frontend (i.e. the > - * state is not Connected) then set the backend state to Closed. > + * state to Closing, but there is no active frontend then set the > + * backend state to Closed. > */ > if (xendev->backend_state == XenbusStateClosing && > - xendev->frontend_state != XenbusStateConnected) { > + !xen_device_state_is_active(state)) { > xen_device_backend_set_state(xendev, XenbusStateClosed); > } > > -- > Anthony PERARD
diff --git a/hw/xen/xen-bus.c b/hw/xen/xen-bus.c index e40500242d..62c127b926 100644 --- a/hw/xen/xen-bus.c +++ b/hw/xen/xen-bus.c @@ -516,6 +516,23 @@ static void xen_device_backend_set_online(XenDevice *xendev, bool online) xen_device_backend_printf(xendev, "online", "%u", online); } +/* + * Tell from the state whether the frontend is likely alive, + * i.e. it will react to a change of state of the backend. + */ +static bool xen_device_state_is_active(enum xenbus_state state) +{ + switch (state) { + case XenbusStateInitWait: + case XenbusStateInitialised: + case XenbusStateConnected: + case XenbusStateClosing: + return true; + default: + return false; + } +} + static void xen_device_backend_changed(void *opaque) { XenDevice *xendev = opaque; @@ -539,11 +556,11 @@ static void xen_device_backend_changed(void *opaque) /* * If the toolstack (or unplug request callback) has set the backend - * state to Closing, but there is no active frontend (i.e. the - * state is not Connected) then set the backend state to Closed. + * state to Closing, but there is no active frontend then set the + * backend state to Closed. */ if (xendev->backend_state == XenbusStateClosing && - xendev->frontend_state != XenbusStateConnected) { + !xen_device_state_is_active(state)) { xen_device_backend_set_state(xendev, XenbusStateClosed); }
When a frontend wants to reset its state and the backend one, it starts with setting "Closing", then waits for the backend (QEMU) to do the same. But when QEMU is setting "Closing" to its state, it triggers an event (xenstore watch) that re-execute xen_device_backend_changed() and set the backend state to "Closed". QEMU should wait for the frontend to set "Closed" before doing the same. Before setting "Closed" to the backend_state, we are also going to check if there is a frontend. If that the case, when the backend state is set to "Closing" the frontend should react and sets its state to "Closing" then "Closed". The backend should wait for that to happen. Fixes: b6af8926fb858c4f1426e5acb2cfc1f0580ec98a Signed-off-by: Anthony PERARD <anthony.perard@citrix.com> --- Cc: qemu-stable@nongnu.org --- Notes: v2: - use a helper - Add InitWait and Initialised to the list of active state hw/xen/xen-bus.c | 23 ++++++++++++++++++++--- 1 file changed, 20 insertions(+), 3 deletions(-)