On Fri, Sep 09, 2016 at 04:14:59PM +0200, Maxime Coquelin wrote:
> Currently, devices are plugged before features are negotiated.
> If the backend doesn't support VIRTIO_F_VERSION_1, the transport
> need to rewind some settings.
>
> This is the case for both PCI and CCW.
> For CCW, a post_plugged callback had been introduced, where
> max_rev field is just updated if VIRTIO_F_VERSION_1 is not
> supported by the backend.
> For PCI, implementing the post_plugged would be much more
> complicated, so the current fix consists in checking whether
> the backend supports VIRTIO_F_VERSION_1 in the backend.
>
> This patch propose to replace existing solutions with a common
> approach by negociating features before ->device_plugged() is
> called. A pre_plugged callback is introduced so that the
> transports can set their supported features.
>
> Cc: Cornelia Huck <cornelia.h...@de.ibm.com>
> Cc: Marcel Apfelbaum <mar...@redhat.com>
> Cc: Michael S. Tsirkin <m...@redhat.com>
> Signed-off-by: Maxime Coquelin <maxime.coque...@redhat.com>
Acked-by: Michael S. Tsirkin <m...@redhat.com>
Looks good - can you pls test and post a non-RFC?
> ---
> Cornelia,
>
> This is what I proposed earlier today.
>
> I have tested it successfully with PCI.
> Does it sound good to you? Would you have a try with CCW?
>
> Note that this is based on my earlier series which fixes PCI.
>
> Thanks,
> Maxime
> ---
> hw/s390x/virtio-ccw.c | 30 +++++++++++++++---------------
> hw/virtio/virtio-bus.c | 9 +++++----
> hw/virtio/virtio-pci.c | 18 ++++++++++++++----
> include/hw/virtio/virtio-bus.h | 10 +++++-----
> 4 files changed, 39 insertions(+), 28 deletions(-)
>
> diff --git a/hw/s390x/virtio-ccw.c b/hw/s390x/virtio-ccw.c
> index a554a24..e10a88d 100644
> --- a/hw/s390x/virtio-ccw.c
> +++ b/hw/s390x/virtio-ccw.c
> @@ -1261,6 +1261,16 @@ static int virtio_ccw_load_config(DeviceState *d,
> QEMUFile *f)
> return 0;
> }
>
> +static void virtio_ccw_pre_plugged(DeviceState *d, Error **errp)
> +{
> + VirtioCcwDevice *dev = VIRTIO_CCW_DEVICE(d);
> + VirtIODevice *vdev = virtio_bus_get_device(&dev->bus);
> +
> + if (dev->max_rev >= 1) {
> + virtio_add_feature(&vdev->host_features, VIRTIO_F_VERSION_1);
> + }
> +}
> +
> /* This is called by virtio-bus just after the device is plugged. */
> static void virtio_ccw_device_plugged(DeviceState *d, Error **errp)
> {
> @@ -1270,6 +1280,10 @@ static void virtio_ccw_device_plugged(DeviceState *d,
> Error **errp)
> SubchDev *sch = ccw_dev->sch;
> int n = virtio_get_num_queues(vdev);
>
> + if (!virtio_has_feature(vdev->host_features, VIRTIO_F_VERSION_1)) {
> + dev->max_rev = 0;
> + }
> +
> if (virtio_get_num_queues(vdev) > VIRTIO_CCW_QUEUE_MAX) {
> error_setg(errp, "The number of virtqueues %d "
> "exceeds ccw limit %d", n,
> @@ -1283,25 +1297,11 @@ static void virtio_ccw_device_plugged(DeviceState *d,
> Error **errp)
>
> sch->id.cu_model = virtio_bus_get_vdev_id(&dev->bus);
>
> - if (dev->max_rev >= 1) {
> - virtio_add_feature(&vdev->host_features, VIRTIO_F_VERSION_1);
> - }
>
> css_generate_sch_crws(sch->cssid, sch->ssid, sch->schid,
> d->hotplugged, 1);
> }
>
> -static void virtio_ccw_post_plugged(DeviceState *d, Error **errp)
> -{
> - VirtioCcwDevice *dev = VIRTIO_CCW_DEVICE(d);
> - VirtIODevice *vdev = virtio_bus_get_device(&dev->bus);
> -
> - if (!virtio_host_has_feature(vdev, VIRTIO_F_VERSION_1)) {
> - /* A backend didn't support modern virtio. */
> - dev->max_rev = 0;
> - }
> -}
> -
> static void virtio_ccw_device_unplugged(DeviceState *d)
> {
> VirtioCcwDevice *dev = VIRTIO_CCW_DEVICE(d);
> @@ -1593,8 +1593,8 @@ static void virtio_ccw_bus_class_init(ObjectClass
> *klass, void *data)
> k->load_queue = virtio_ccw_load_queue;
> k->save_config = virtio_ccw_save_config;
> k->load_config = virtio_ccw_load_config;
> + k->pre_plugged = virtio_ccw_pre_plugged;
> k->device_plugged = virtio_ccw_device_plugged;
> - k->post_plugged = virtio_ccw_post_plugged;
> k->device_unplugged = virtio_ccw_device_unplugged;
> k->ioeventfd_started = virtio_ccw_ioeventfd_started;
> k->ioeventfd_set_started = virtio_ccw_ioeventfd_set_started;
> diff --git a/hw/virtio/virtio-bus.c b/hw/virtio/virtio-bus.c
> index a85b7c8..9d2111f 100644
> --- a/hw/virtio/virtio-bus.c
> +++ b/hw/virtio/virtio-bus.c
> @@ -49,16 +49,17 @@ void virtio_bus_device_plugged(VirtIODevice *vdev, Error
> **errp)
>
> DPRINTF("%s: plug device.\n", qbus->name);
>
> - if (klass->device_plugged != NULL) {
> - klass->device_plugged(qbus->parent, errp);
> + if (klass->pre_plugged != NULL) {
> + klass->pre_plugged(qbus->parent, errp);
> }
>
> /* Get the features of the plugged device. */
> assert(vdc->get_features != NULL);
> vdev->host_features = vdc->get_features(vdev, vdev->host_features,
> errp);
> - if (klass->post_plugged != NULL) {
> - klass->post_plugged(qbus->parent, errp);
> +
> + if (klass->device_plugged != NULL) {
> + klass->device_plugged(qbus->parent, errp);
> }
> }
>
> diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
> index 9e88d7b..07e6c60 100644
> --- a/hw/virtio/virtio-pci.c
> +++ b/hw/virtio/virtio-pci.c
> @@ -1569,6 +1569,18 @@ static void
> virtio_pci_modern_io_region_unmap(VirtIOPCIProxy *proxy,
> ®ion->mr);
> }
>
> +static void virtio_pci_pre_plugged(DeviceState *d, Error **errp)
> +{
> + VirtIOPCIProxy *proxy = VIRTIO_PCI(d);
> + VirtIODevice *vdev = virtio_bus_get_device(&proxy->bus);
> +
> + if (virtio_pci_modern(proxy)) {
> + virtio_add_feature(&vdev->host_features, VIRTIO_F_VERSION_1);
> + }
> +
> + virtio_add_feature(&vdev->host_features, VIRTIO_F_BAD_FEATURE);
> +}
> +
> /* This is called by virtio-bus just after the device is plugged. */
> static void virtio_pci_device_plugged(DeviceState *d, Error **errp)
> {
> @@ -1585,7 +1597,7 @@ static void virtio_pci_device_plugged(DeviceState *d,
> Error **errp)
> * Virtio capabilities present without
> * VIRTIO_F_VERSION_1 confuses guests
> */
> - if (!virtio_test_backend_virtio_1(vdev, errp)) {
> + if (!virtio_has_feature(vdev->host_features, VIRTIO_F_VERSION_1)) {
> virtio_pci_disable_modern(proxy);
> }
>
> @@ -1637,7 +1649,6 @@ static void virtio_pci_device_plugged(DeviceState *d,
> Error **errp)
>
> struct virtio_pci_cfg_cap *cfg_mask;
>
> - virtio_add_feature(&vdev->host_features, VIRTIO_F_VERSION_1);
> virtio_pci_modern_regions_init(proxy);
>
> virtio_pci_modern_mem_region_map(proxy, &proxy->common, &cap);
> @@ -1702,8 +1713,6 @@ static void virtio_pci_device_plugged(DeviceState *d,
> Error **errp)
> if (!kvm_has_many_ioeventfds()) {
> proxy->flags &= ~VIRTIO_PCI_FLAG_USE_IOEVENTFD;
> }
> -
> - virtio_add_feature(&vdev->host_features, VIRTIO_F_BAD_FEATURE);
> }
>
> static void virtio_pci_device_unplugged(DeviceState *d)
> @@ -2459,6 +2468,7 @@ static void virtio_pci_bus_class_init(ObjectClass
> *klass, void *data)
> k->query_guest_notifiers = virtio_pci_query_guest_notifiers;
> k->set_guest_notifiers = virtio_pci_set_guest_notifiers;
> k->vmstate_change = virtio_pci_vmstate_change;
> + k->pre_plugged = virtio_pci_pre_plugged;
> k->device_plugged = virtio_pci_device_plugged;
> k->device_unplugged = virtio_pci_device_unplugged;
> k->query_nvectors = virtio_pci_query_nvectors;
> diff --git a/include/hw/virtio/virtio-bus.h b/include/hw/virtio/virtio-bus.h
> index f3e5ef3..24caa0a 100644
> --- a/include/hw/virtio/virtio-bus.h
> +++ b/include/hw/virtio/virtio-bus.h
> @@ -54,16 +54,16 @@ typedef struct VirtioBusClass {
> int (*set_guest_notifiers)(DeviceState *d, int nvqs, bool assign);
> void (*vmstate_change)(DeviceState *d, bool running);
> /*
> + * Expose the features the transport layer supports before
> + * the negotiation takes place.
> + */
> + void (*pre_plugged)(DeviceState *d, Error **errp);
> + /*
> * transport independent init function.
> * This is called by virtio-bus just after the device is plugged.
> */
> void (*device_plugged)(DeviceState *d, Error **errp);
> /*
> - * Re-evaluate setup after feature bits have been validated
> - * by the device backend.
> - */
> - void (*post_plugged)(DeviceState *d, Error **errp);
> - /*
> * transport independent exit function.
> * This is called by virtio-bus just before the device is unplugged.
> */
> --
> 2.7.4
