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have been queried that can handle the VERSION_1 bit being withdrawn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>
---
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
