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).
Signed-off-by: Daniil Tatianin <d-tatianin@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++) {
--
2.25.1On 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.norwitz@nutanix.com>
> Signed-off-by: Daniil Tatianin <d-tatianin@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
>
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