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[88.10.103.181]) by smtp.gmail.com with ESMTPSA id x186sm2061050wmg.8.2020.06.09.00.59.36 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 09 Jun 2020 00:59:36 -0700 (PDT) Subject: Re: [PATCH v2 04/58] qdev: New qdev_new(), qdev_realize(), etc. To: Markus Armbruster , qemu-devel@nongnu.org References: <20200529134523.8477-1-armbru@redhat.com> <20200529134523.8477-5-armbru@redhat.com> From: =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= Autocrypt: addr=philmd@redhat.com; keydata= mQINBDXML8YBEADXCtUkDBKQvNsQA7sDpw6YLE/1tKHwm24A1au9Hfy/OFmkpzo+MD+dYc+7 bvnqWAeGweq2SDq8zbzFZ1gJBd6+e5v1a/UrTxvwBk51yEkadrpRbi+r2bDpTJwXc/uEtYAB GvsTZMtiQVA4kRID1KCdgLa3zztPLCj5H1VZhqZsiGvXa/nMIlhvacRXdbgllPPJ72cLUkXf z1Zu4AkEKpccZaJspmLWGSzGu6UTZ7UfVeR2Hcc2KI9oZB1qthmZ1+PZyGZ/Dy+z+zklC0xl XIpQPmnfy9+/1hj1LzJ+pe3HzEodtlVA+rdttSvA6nmHKIt8Ul6b/h1DFTmUT1lN1WbAGxmg CH1O26cz5nTrzdjoqC/b8PpZiT0kO5MKKgiu5S4PRIxW2+RA4H9nq7nztNZ1Y39bDpzwE5Sp bDHzd5owmLxMLZAINtCtQuRbSOcMjZlg4zohA9TQP9krGIk+qTR+H4CV22sWldSkVtsoTaA2 qNeSJhfHQY0TyQvFbqRsSNIe2gTDzzEQ8itsmdHHE/yzhcCVvlUzXhAT6pIN0OT+cdsTTfif MIcDboys92auTuJ7U+4jWF1+WUaJ8gDL69ThAsu7mGDBbm80P3vvUZ4fQM14NkxOnuGRrJxO qjWNJ2ZUxgyHAh5TCxMLKWZoL5hpnvx3dF3Ti9HW2dsUUWICSQARAQABtDJQaGlsaXBwZSBN YXRoaWV1LURhdWTDqSAoUGhpbCkgPHBoaWxtZEByZWRoYXQuY29tPokCVQQTAQgAPwIbDwYL CQgHAwIGFQgCCQoLBBYCAwECHgECF4AWIQSJweePYB7obIZ0lcuio/1u3q3A3gUCXsfWwAUJ KtymWgAKCRCio/1u3q3A3ircD/9Vjh3aFNJ3uF3hddeoFg1H038wZr/xi8/rX27M1Vj2j9VH 0B8Olp4KUQw/hyO6kUxqkoojmzRpmzvlpZ0cUiZJo2bQIWnvScyHxFCv33kHe+YEIqoJlaQc JfKYlbCoubz+02E2A6bFD9+BvCY0LBbEj5POwyKGiDMjHKCGuzSuDRbCn0Mz4kCa7nFMF5Jv piC+JemRdiBd6102ThqgIsyGEBXuf1sy0QIVyXgaqr9O2b/0VoXpQId7yY7OJuYYxs7kQoXI 6WzSMpmuXGkmfxOgbc/L6YbzB0JOriX0iRClxu4dEUg8Bs2pNnr6huY2Ft+qb41RzCJvvMyu gS32LfN0bTZ6Qm2A8ayMtUQgnwZDSO23OKgQWZVglGliY3ezHZ6lVwC24Vjkmq/2yBSLakZE 6DZUjZzCW1nvtRK05ebyK6tofRsx8xB8pL/kcBb9nCuh70aLR+5cmE41X4O+MVJbwfP5s/RW 9BFSL3qgXuXso/3XuWTQjJJGgKhB6xXjMmb1J4q/h5IuVV4juv1Fem9sfmyrh+Wi5V1IzKI7 RPJ3KVb937eBgSENk53P0gUorwzUcO+ASEo3Z1cBKkJSPigDbeEjVfXQMzNt0oDRzpQqH2vp apo2jHnidWt8BsckuWZpxcZ9+/9obQ55DyVQHGiTN39hkETy3Emdnz1JVHTU0Q== Message-ID: Date: Tue, 9 Jun 2020 09:59:35 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: <20200529134523.8477-5-armbru@redhat.com> Content-Language: en-US X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=207.211.31.120; envelope-from=philmd@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/06/09 01:38:49 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_PASS=-0.001, URIBL_BLOCKED=0.001 autolearn=_AUTOLEARN X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Peter Maydell , "Michael S . Tsirkin" , Alistair Francis , Mark Cave-Ayland , Gerd Hoffmann , John Snow , David Gibson Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 5/29/20 3:44 PM, Markus Armbruster wrote: > We commonly plug devices into their bus right when we create them, > like this: > > dev = qdev_create(bus, type_name); > > Note that @dev is a weak reference. The reference from @bus to @dev > is the only strong one. > > We realize at some later time, either with > > object_property_set_bool(OBJECT(dev), true, "realized", errp); > > or its convenience wrapper > > qdev_init_nofail(dev); > > If @dev still has no QOM parent then, realizing makes the > /machine/unattached/ orphanage its QOM parent. > > Note that the device returned by qdev_create() is plugged into a bus, > but doesn't have a QOM parent, yet. Until it acquires one, > unrealizing the bus will hang in bus_unparent(): > > while ((kid = QTAILQ_FIRST(&bus->children)) != NULL) { > DeviceState *dev = kid->child; > object_unparent(OBJECT(dev)); > } > > object_unparent() does nothing when its argument has no QOM parent, > and the loop spins forever. > > Device state "no QOM parent, but plugged into bus" is dangerous. > > Paolo suggested to delay plugging into the bus until realize. We need > to plug into the parent bus before we call the device's realize > method, in case it uses the parent bus. So the dangerous state still > exists, but only within realization, where we can manage it safely. > > This commit creates infrastructure to do this: > > dev = qdev_new(type_name); > ... > qdev_realize_and_unref(dev, bus, errp) > > Note that @dev becomes a strong reference here. > qdev_realize_and_unref() drops it. There is also plain > qdev_realize(), which doesn't drop it. > > The remainder of this series will convert all users to this new > interface. > > Cc: Michael S. Tsirkin > Cc: Marcel Apfelbaum > Cc: Alistair Francis > Cc: Gerd Hoffmann > Cc: Mark Cave-Ayland > Cc: David Gibson > Signed-off-by: Markus Armbruster > Acked-by: Gerd Hoffmann > --- > include/hw/qdev-core.h | 11 +++++- > hw/core/bus.c | 14 +++++++ > hw/core/qdev.c | 90 ++++++++++++++++++++++++++++++++++++++++++ > 3 files changed, 114 insertions(+), 1 deletion(-) > > diff --git a/include/hw/qdev-core.h b/include/hw/qdev-core.h > index b870b27966..fba29308f7 100644 > --- a/include/hw/qdev-core.h > +++ b/include/hw/qdev-core.h > @@ -57,7 +57,7 @@ typedef void (*BusUnrealize)(BusState *bus); > * After successful realization, setting static properties will fail. > * > * As an interim step, the #DeviceState:realized property can also be > - * set with qdev_init_nofail(). > + * set with qdev_realize() or qdev_init_nofail(). > * In the future, devices will propagate this state change to their children > * and along busses they expose. > * The point in time will be deferred to machine creation, so that values > @@ -322,7 +322,13 @@ compat_props_add(GPtrArray *arr, > > DeviceState *qdev_create(BusState *bus, const char *name); > DeviceState *qdev_try_create(BusState *bus, const char *name); > +DeviceState *qdev_new(const char *name); > +DeviceState *qdev_try_new(const char *name); > void qdev_init_nofail(DeviceState *dev); > +bool qdev_realize(DeviceState *dev, BusState *bus, Error **errp); > +bool qdev_realize_and_unref(DeviceState *dev, BusState *bus, Error **errp); > +void qdev_unrealize(DeviceState *dev); > + > void qdev_set_legacy_instance_id(DeviceState *dev, int alias_id, > int required_for_version); > HotplugHandler *qdev_get_bus_hotplug_handler(DeviceState *dev); > @@ -411,6 +417,9 @@ typedef int (qdev_walkerfn)(DeviceState *dev, void *opaque); > void qbus_create_inplace(void *bus, size_t size, const char *typename, > DeviceState *parent, const char *name); > BusState *qbus_create(const char *typename, DeviceState *parent, const char *name); > +bool qbus_realize(BusState *bus, Error **errp); > +void qbus_unrealize(BusState *bus); > + > /* Returns > 0 if either devfn or busfn skip walk somewhere in cursion, > * < 0 if either devfn or busfn terminate walk somewhere in cursion, > * 0 otherwise. */ > diff --git a/hw/core/bus.c b/hw/core/bus.c > index 33a4443217..6f6071f5fa 100644 > --- a/hw/core/bus.c > +++ b/hw/core/bus.c > @@ -164,6 +164,20 @@ BusState *qbus_create(const char *typename, DeviceState *parent, const char *nam > return bus; > } > > +bool qbus_realize(BusState *bus, Error **errp) > +{ > + Error *err = NULL; > + > + object_property_set_bool(OBJECT(bus), true, "realized", &err); > + error_propagate(errp, err); > + return !err; > +} > + > +void qbus_unrealize(BusState *bus) > +{ > + object_property_set_bool(OBJECT(bus), false, "realized", &error_abort); > +} > + > static bool bus_get_realized(Object *obj, Error **errp) > { > BusState *bus = BUS(obj); > diff --git a/hw/core/qdev.c b/hw/core/qdev.c > index a68ba674db..f2c5cee278 100644 > --- a/hw/core/qdev.c > +++ b/hw/core/qdev.c > @@ -176,6 +176,32 @@ DeviceState *qdev_try_create(BusState *bus, const char *type) > return dev; > } > > +/* > + * Create a device on the heap. > + * A type @name must exist. > + * This only initializes the device state structure and allows > + * properties to be set. The device still needs to be realized. See > + * qdev-core.h. > + */ > +DeviceState *qdev_new(const char *name) > +{ > + return DEVICE(object_new(name)); > +} > + > +/* > + * Try to create a device on the heap. > + * This is like qdev_new(), except it returns %NULL when type @name > + * does not exist. > + */ > +DeviceState *qdev_try_new(const char *name) > +{ > + if (!object_class_by_name(name)) { > + return NULL; > + } > + > + return DEVICE(object_new(name)); Or: return qdev_new(name); > +} > + > static QTAILQ_HEAD(, DeviceListener) device_listeners > = QTAILQ_HEAD_INITIALIZER(device_listeners); > > @@ -427,6 +453,66 @@ void qdev_init_nofail(DeviceState *dev) > object_unref(OBJECT(dev)); > } > > +/* > + * Realize @dev. > + * @dev must not be plugged into a bus. > + * Plug @dev into @bus if non-null, else into the main system bus. So this is the historical part... > + * This takes a reference to @dev. > + * If @dev has no QOM parent, make one up, taking another reference. > + * On success, return true. > + * On failure, store an error through @errp and return false. > + */ > +bool qdev_realize(DeviceState *dev, BusState *bus, Error **errp) > +{ > + Error *err = NULL; > + > + assert(!dev->realized && !dev->parent_bus); > + > + if (!bus) { > + /* > + * Assert that the device really is a SysBusDevice before we > + * put it onto the sysbus. Non-sysbus devices which aren't > + * being put onto a bus should be realized with > + * object_property_set_bool(OBJECT(dev), true, "realized", > + * errp); > + */ > + g_assert(object_dynamic_cast(OBJECT(dev), TYPE_SYS_BUS_DEVICE)); > + bus = sysbus_get_default(); OK, so we take a QDEV argument. If we have a BUS argument, we use it as parent bus. If we don't have a BUS argument, we expect the device is a SYSBUSDEV and use sysbus_get_default as parent bus. So we can not use this function realize a QDEV which is not a SYSBUSDEV. For that, we have to use 'object_property_set_bool(OBJECT(QDEV), true, "realized")'. IOW: - to realize a QDEV, we have to use the OBJECT API, - to realize a SYSBUSDEV, we have to use the QDEV API. I'm not suggesting you to clean that now, I'm simply taking notes about future improvements, because this is really not clear for new contributors. > + } > + > + qdev_set_parent_bus(dev, bus); > + > + object_property_set_bool(OBJECT(dev), true, "realized", &err); > + if (err) { > + error_propagate(errp, err); > + } > + return !err; > +} > + > +/* > + * Realize @dev and drop a reference. > + * This is like qdev_realize(), except the caller must hold a > + * (private) reference, which is dropped on return regardless of > + * success or failure. Intended use: > + * dev = qdev_new(); > + * [...] > + * qdev_realize_and_unref(dev, bus, errp); > + * Now @dev can go away without further ado. > + */ > +bool qdev_realize_and_unref(DeviceState *dev, BusState *bus, Error **errp) > +{ > + bool ret; > + > + ret = qdev_realize(dev, bus, errp); > + object_unref(OBJECT(dev)); > + return ret; > +} > + > +void qdev_unrealize(DeviceState *dev) > +{ > + object_property_set_bool(OBJECT(dev), false, "realized", &error_abort); > +} > + > static int qdev_assert_realized_properly(Object *obj, void *opaque) > { > DeviceState *dev = DEVICE(object_dynamic_cast(obj, TYPE_DEVICE)); > @@ -1002,6 +1088,10 @@ post_realize_fail: > fail: > error_propagate(errp, local_err); > if (unattached_parent) { > + /* > + * Beware, this doesn't just revert > + * object_property_add_child(), it also runs bus_remove()! > + */ > object_unparent(OBJECT(dev)); > unattached_count--; > } > Reviewed-by: Philippe Mathieu-Daudé