Sorry to chime in late in the game. For some reason I couldn't get to
most emails for this discussion (I only subscribed to the virtualization
list), while I was taking off amongst the past few weeks.
It looks to me this patch is incomplete. Noted down the way in
vdpa_dev_net_config_fill(), we have the following:
features = vdev->config->get_driver_features(vdev);
if (nla_put_u64_64bit(msg, VDPA_ATTR_DEV_NEGOTIATED_FEATURES, features,
VDPA_ATTR_PAD))
return -EMSGSIZE;
Making call to .get_driver_features() doesn't make sense when feature
negotiation isn't complete. Neither should present negotiated_features
to userspace before negotiation is done.
Similarly, max_vqp through vdpa_dev_net_mq_config_fill() probably should
not show before negotiation is done - it depends on driver features
negotiated.
Last but not the least, this "vdpa dev config" command was not designed
to display the real config space register values in the first place.
Quoting the vdpa-dev(8) man page:
vdpa dev config show - Show configuration of specific device or all
devices.
DEV - specifies the vdpa device to show its configuration. If this
argument is omitted all devices configuration is listed.
It doesn't say anything about configuration space or register values in
config space. As long as it can convey the config attribute when
instantiating vDPA device instance, and more importantly, the config can
be easily imported from or exported to userspace tools when trying to
reconstruct vdpa instance intact on destination host for live migration,
IMHO in my personal interpretation it doesn't matter what the config
space may present. It may be worth while adding a new debug command to
expose the real register value, but that's another story.
Having said, please consider to drop the Fixes tag, as appears to me
you're proposing a new feature rather than fixing a real issue.
Thanks,
-Siwei
On 7/1/2022 3:12 PM, Parav Pandit via Virtualization wrote:
From: Zhu Lingshan<[email protected]>
Sent: Friday, July 1, 2022 9:28 AM
Users may want to query the config space of a vDPA device, to choose a
appropriate one for a certain guest. This means the users need to read the
config space before FEATURES_OK, and the existence of config space
contents does not depend on FEATURES_OK.
The spec says:
The device MUST allow reading of any device-specific configuration field
before FEATURES_OK is set by the driver. This includes fields which are
conditional on feature bits, as long as those feature bits are offered by the
device.
Fixes: 30ef7a8ac8a07 (vdpa: Read device configuration only if FEATURES_OK)
Fix is fine, but fixes tag needs correction described below.
Above commit id is 13 letters should be 12.
And
It should be in format
Fixes: 30ef7a8ac8a0 ("vdpa: Read device configuration only if FEATURES_OK")
Please use checkpatch.pl script before posting the patches to catch these
errors.
There is a bot that looks at the fixes tag and identifies the right kernel
version to apply this fix.
Signed-off-by: Zhu Lingshan<[email protected]>
---
drivers/vdpa/vdpa.c | 8 --------
1 file changed, 8 deletions(-)
diff --git a/drivers/vdpa/vdpa.c b/drivers/vdpa/vdpa.c index
9b0e39b2f022..d76b22b2f7ae 100644
--- a/drivers/vdpa/vdpa.c
+++ b/drivers/vdpa/vdpa.c
@@ -851,17 +851,9 @@ vdpa_dev_config_fill(struct vdpa_device *vdev,
struct sk_buff *msg, u32 portid, {
u32 device_id;
void *hdr;
- u8 status;
int err;
down_read(&vdev->cf_lock);
- status = vdev->config->get_status(vdev);
- if (!(status & VIRTIO_CONFIG_S_FEATURES_OK)) {
- NL_SET_ERR_MSG_MOD(extack, "Features negotiation not
completed");
- err = -EAGAIN;
- goto out;
- }
-
hdr = genlmsg_put(msg, portid, seq, &vdpa_nl_family, flags,
VDPA_CMD_DEV_CONFIG_GET);
if (!hdr) {
--
2.31.1
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