On Wed, Dec 02, 2015 at 03:09:58PM +0100, Cornelia Huck wrote:
> If you run a qemu advertising VERSION_1 with an old kernel where
> vhost did not yet support VERSION_1, you'll end up with a device
> that is {modern pci|ccw revision 1} but does not advertise VERSION_1.
> This is not a sensible configuration and is rejected by the Linux
> guest drivers.
>
> To fix this, add a ->post_plugged() callback invoked after features
> have been queried that can handle the VERSION_1 bit being withdrawn
> and change pci (only setup modern if VERSION_1 is still present) and
> ccw (fall back to revision 0 if VERSION_1 is gone).
>
> Signed-off-by: Cornelia Huck <cornelia.h...@de.ibm.com>
Unfortunately this is too late: we need to know
whether modern will be supported to know whether
to add the pci express capability :(
Maybe this should be moved into plugged
callback?
> ---
> Michael: I think this should go into 2.5, as otherwise ccw (which
> defaults to virtio-1 with 2.5) will be broken with old host kernels.
> I need someone to give virtio-pci some testing, as I do not have
> a proper setup for that. ccw is working fine.
>
> Changes from initial writeup:
> - Move pci-modern init to post_plugged instead of undoing [Jason]
> - Add a proper patch description + signoff
> - Add some comments
> ---
> hw/s390x/virtio-ccw.c | 12 ++++++
> hw/virtio/virtio-bus.c | 3 ++
> hw/virtio/virtio-pci.c | 96
> ++++++++++++++++++++++++++----------------
> include/hw/virtio/virtio-bus.h | 5 +++
> 4 files changed, 80 insertions(+), 36 deletions(-)
>
> diff --git a/hw/s390x/virtio-ccw.c b/hw/s390x/virtio-ccw.c
> index fb103b7..63da303 100644
> --- a/hw/s390x/virtio-ccw.c
> +++ b/hw/s390x/virtio-ccw.c
> @@ -1555,6 +1555,17 @@ static void virtio_ccw_device_plugged(DeviceState *d,
> Error **errp)
> 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);
> @@ -1891,6 +1902,7 @@ static void virtio_ccw_bus_class_init(ObjectClass
> *klass, void *data)
> k->save_config = virtio_ccw_save_config;
> k->load_config = virtio_ccw_load_config;
> k->device_plugged = virtio_ccw_device_plugged;
> + k->post_plugged = virtio_ccw_post_plugged;
> k->device_unplugged = virtio_ccw_device_unplugged;
> }
>
> diff --git a/hw/virtio/virtio-bus.c b/hw/virtio/virtio-bus.c
> index febda76..81c7cdd 100644
> --- a/hw/virtio/virtio-bus.c
> +++ b/hw/virtio/virtio-bus.c
> @@ -56,6 +56,9 @@ void virtio_bus_device_plugged(VirtIODevice *vdev, Error
> **errp)
> 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);
> + }
> }
>
> /* Reset the virtio_bus */
> diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
> index dd48562..af59496 100644
> --- a/hw/virtio/virtio-pci.c
> +++ b/hw/virtio/virtio-pci.c
> @@ -1626,7 +1626,6 @@ static void virtio_pci_device_plugged(DeviceState *d,
> Error **errp)
> VirtioBusState *bus = &proxy->bus;
> bool legacy = !(proxy->flags & VIRTIO_PCI_FLAG_DISABLE_LEGACY);
> bool modern = !(proxy->flags & VIRTIO_PCI_FLAG_DISABLE_MODERN);
> - bool modern_pio = proxy->flags & VIRTIO_PCI_FLAG_MODERN_PIO_NOTIFY;
> uint8_t *config;
> uint32_t size;
> VirtIODevice *vdev = virtio_bus_get_device(&proxy->bus);
> @@ -1653,6 +1652,65 @@ static void virtio_pci_device_plugged(DeviceState *d,
> Error **errp)
>
>
> if (modern) {
> + virtio_add_feature(&vdev->host_features, VIRTIO_F_VERSION_1);
> + /* Let's see if this feature bit sticks before doing further init. */
> + }
> +
> + if (proxy->nvectors) {
> + int err = msix_init_exclusive_bar(&proxy->pci_dev, proxy->nvectors,
> + proxy->msix_bar);
> + if (err) {
> + /* Notice when a system that supports MSIx can't initialize it.
> */
> + if (err != -ENOTSUP) {
> + error_report("unable to init msix vectors to %" PRIu32,
> + proxy->nvectors);
> + }
> + proxy->nvectors = 0;
> + }
> + }
> +
> + proxy->pci_dev.config_write = virtio_write_config;
> + proxy->pci_dev.config_read = virtio_read_config;
> +
> + if (legacy) {
> + size = VIRTIO_PCI_REGION_SIZE(&proxy->pci_dev)
> + + virtio_bus_get_vdev_config_len(bus);
> + size = pow2ceil(size);
> +
> + memory_region_init_io(&proxy->bar, OBJECT(proxy),
> + &virtio_pci_config_ops,
> + proxy, "virtio-pci", size);
> +
> + pci_register_bar(&proxy->pci_dev, proxy->legacy_io_bar,
> + PCI_BASE_ADDRESS_SPACE_IO, &proxy->bar);
> + }
> +
> + 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_post_plugged(DeviceState *d, Error **errp)
> +{
> + VirtIOPCIProxy *proxy = VIRTIO_PCI(d);
> + bool legacy = !(proxy->flags & VIRTIO_PCI_FLAG_DISABLE_LEGACY);
> + bool modern = !(proxy->flags & VIRTIO_PCI_FLAG_DISABLE_MODERN);
> + bool modern_pio = proxy->flags & VIRTIO_PCI_FLAG_MODERN_PIO_NOTIFY;
> + VirtIODevice *vdev = virtio_bus_get_device(&proxy->bus);
> +
> + if (modern && !virtio_host_has_feature(vdev, VIRTIO_F_VERSION_1)) {
> + /* A backend didn't support modern virtio. */
> + if (legacy) {
> + proxy->flags |= VIRTIO_PCI_FLAG_DISABLE_MODERN;
> + modern = false;
> + } else {
> + error_setg(errp, "can't fall back to legacy virtio");
> + return;
> + }
> + }
> + if (modern) {
> struct virtio_pci_cap cap = {
> .cap_len = sizeof cap,
> };
> @@ -1672,7 +1730,6 @@ 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);
> @@ -1705,40 +1762,6 @@ static void virtio_pci_device_plugged(DeviceState *d,
> Error **errp)
> pci_set_long(cfg_mask->pci_cfg_data, ~0x0);
> }
>
> - if (proxy->nvectors) {
> - int err = msix_init_exclusive_bar(&proxy->pci_dev, proxy->nvectors,
> - proxy->msix_bar);
> - if (err) {
> - /* Notice when a system that supports MSIx can't initialize it.
> */
> - if (err != -ENOTSUP) {
> - error_report("unable to init msix vectors to %" PRIu32,
> - proxy->nvectors);
> - }
> - proxy->nvectors = 0;
> - }
> - }
> -
> - proxy->pci_dev.config_write = virtio_write_config;
> - proxy->pci_dev.config_read = virtio_read_config;
> -
> - if (legacy) {
> - size = VIRTIO_PCI_REGION_SIZE(&proxy->pci_dev)
> - + virtio_bus_get_vdev_config_len(bus);
> - size = pow2ceil(size);
> -
> - memory_region_init_io(&proxy->bar, OBJECT(proxy),
> - &virtio_pci_config_ops,
> - proxy, "virtio-pci", size);
> -
> - pci_register_bar(&proxy->pci_dev, proxy->legacy_io_bar,
> - PCI_BASE_ADDRESS_SPACE_IO, &proxy->bar);
> - }
> -
> - 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)
> @@ -2474,6 +2497,7 @@ static void virtio_pci_bus_class_init(ObjectClass
> *klass, void *data)
> k->set_guest_notifiers = virtio_pci_set_guest_notifiers;
> k->vmstate_change = virtio_pci_vmstate_change;
> k->device_plugged = virtio_pci_device_plugged;
> + k->post_plugged = virtio_pci_post_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 6c3d4cb..3f2c136 100644
> --- a/include/hw/virtio/virtio-bus.h
> +++ b/include/hw/virtio/virtio-bus.h
> @@ -60,6 +60,11 @@ typedef struct VirtioBusClass {
> */
> 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.
> */
> --
> 2.3.9
