On Fri, Aug 26, 2022 at 05:32:48PM +0300, Daniil Tatianin wrote: > Make vhost-user-blk backwards compatible when migrating from older VMs > running with modern features turned off, the same way it was done for > virtio-blk in 20764be0421c ("virtio-blk: set config size depending on the > features enabled") > > It's currently impossible to migrate from an older VM with > vhost-user-blk (with disable-legacy=off) because of errors like this: > > qemu-system-x86_64: get_pci_config_device: Bad config data: i=0x10 read: 41 > device: 1 cmask: ff wmask: 80 w1cmask:0 > qemu-system-x86_64: Failed to load PCIDevice:config > qemu-system-x86_64: Failed to load virtio-blk:virtio > qemu-system-x86_64: error while loading state for instance 0x0 of device > '0000:00:05.0:00.0:02.0/virtio-blk' > qemu-system-x86_64: load of migration failed: Invalid argument > > This is caused by the newer (destination) VM requiring a bigger BAR0 > alignment because it has to cover a bigger configuration space, which > isn't actually needed since those additional config fields are not > active (write-zeroes/discard). >
With the relevant meson.build and MAINTAINERS bits rebased here: Reviewed-by: Raphael Norwitz <raphael.norw...@nutanix.com> > Signed-off-by: Daniil Tatianin <d-tatia...@yandex-team.ru> > --- > hw/block/vhost-user-blk.c | 17 ++++++++++------- > 1 file changed, 10 insertions(+), 7 deletions(-) > > diff --git a/hw/block/vhost-user-blk.c b/hw/block/vhost-user-blk.c > index 0d916edefa..8dd063eb96 100644 > --- a/hw/block/vhost-user-blk.c > +++ b/hw/block/vhost-user-blk.c > @@ -23,6 +23,7 @@ > #include "hw/qdev-core.h" > #include "hw/qdev-properties.h" > #include "hw/qdev-properties-system.h" > +#include "hw/virtio/virtio-blk-common.h" > #include "hw/virtio/vhost.h" > #include "hw/virtio/vhost-user-blk.h" > #include "hw/virtio/virtio.h" > @@ -63,7 +64,7 @@ static void vhost_user_blk_update_config(VirtIODevice > *vdev, uint8_t *config) > /* Our num_queues overrides the device backend */ > virtio_stw_p(vdev, &s->blkcfg.num_queues, s->num_queues); > > - memcpy(config, &s->blkcfg, sizeof(struct virtio_blk_config)); > + memcpy(config, &s->blkcfg, vdev->config_len); > } > > static void vhost_user_blk_set_config(VirtIODevice *vdev, const uint8_t > *config) > @@ -92,12 +93,12 @@ static int vhost_user_blk_handle_config_change(struct > vhost_dev *dev) > { > int ret; > struct virtio_blk_config blkcfg; > + VirtIODevice *vdev = dev->vdev; > VHostUserBlk *s = VHOST_USER_BLK(dev->vdev); > Error *local_err = NULL; > > ret = vhost_dev_get_config(dev, (uint8_t *)&blkcfg, > - sizeof(struct virtio_blk_config), > - &local_err); > + vdev->config_len, &local_err); > if (ret < 0) { > error_report_err(local_err); > return ret; > @@ -106,7 +107,7 @@ static int vhost_user_blk_handle_config_change(struct > vhost_dev *dev) > /* valid for resize only */ > if (blkcfg.capacity != s->blkcfg.capacity) { > s->blkcfg.capacity = blkcfg.capacity; > - memcpy(dev->vdev->config, &s->blkcfg, sizeof(struct > virtio_blk_config)); > + memcpy(dev->vdev->config, &s->blkcfg, vdev->config_len); > virtio_notify_config(dev->vdev); > } > > @@ -442,7 +443,7 @@ static int vhost_user_blk_realize_connect(VHostUserBlk > *s, Error **errp) > assert(s->connected); > > ret = vhost_dev_get_config(&s->dev, (uint8_t *)&s->blkcfg, > - sizeof(struct virtio_blk_config), errp); > + s->parent_obj.config_len, errp); > if (ret < 0) { > qemu_chr_fe_disconnect(&s->chardev); > vhost_dev_cleanup(&s->dev); > @@ -457,6 +458,7 @@ static void vhost_user_blk_device_realize(DeviceState > *dev, Error **errp) > ERRP_GUARD(); > VirtIODevice *vdev = VIRTIO_DEVICE(dev); > VHostUserBlk *s = VHOST_USER_BLK(vdev); > + size_t config_size; > int retries; > int i, ret; > > @@ -487,8 +489,9 @@ static void vhost_user_blk_device_realize(DeviceState > *dev, Error **errp) > return; > } > > - virtio_init(vdev, VIRTIO_ID_BLOCK, > - sizeof(struct virtio_blk_config)); > + config_size = virtio_get_config_size(&virtio_blk_cfg_size_params, > + vdev->host_features); > + virtio_init(vdev, VIRTIO_ID_BLOCK, config_size); > > s->virtqs = g_new(VirtQueue *, s->num_queues); > for (i = 0; i < s->num_queues; i++) { > -- > 2.25.1 >