On 2/26/26 20:20, Peter Xu wrote:
On Thu, Feb 26, 2026 at 12:47:55PM +0500, Alexandr Moshkov wrote:
Yes, looks like it happens because migration stream for "virtio-blk" looks
like this:
[virtio-blk header] [virtio-blk fields] [virtio-blk subsections]
"virtio-blk" contains "virtio" field, so migration stream is:
[virtio-blk header] [virtio header] [virtio fields] [virtio subsections]
[virtio-blk subsections]
And when we load the subsections of the "virtio" device,
vmstate_subsection_load() uses qemu_peek_byte() to try to figure out if this
is his subsection. This is where we encounter an error.
Thus, the error occurs due to the fact that vmsd does not know how many
subsections it has when loading (this does not appear anywhere in the
migration stream), so it tries to load all the appropriate ones by names.
OK I see, thanks for the details.
I think I missed one important thing, that we don't treat
trace_vmstate_subsection_load_bad("(prefix)") as errors.. instead we
fallback to the upper layer by returning zero.
Could you put most of above reply into the commit message? I think it may
help people understand the commit.
We could also add one comment right above the extra "/" check in code, to
make sure nobody will accidentally remove it.
Thanks,
Okay, I'll do that. Thanks!
