[pve-devel] [PATCH qemu-server 2/2] fix #6556: vm status: fix querying block stats
Fiona Ebner
f.ebner at proxmox.com
Wed Jul 23 13:10:47 CEST 2025
With the switch to '-blockdev', the 'device' property in the return
value of the 'query-blockstats' QMP command is not initialized. This
can be seen in the QEMU source code (the device property is the name
of the block backend and blk->name is assigned a value only in a code
path reached via drive_new()). This was done to avoid confusion/clashes
with node names, because they live in the same namespace as block
backend names.
The node names cannot be relied on either, because an empty CD-ROM
drive does not have an associated block node. So use the qdev ID as a
fallback.
The stats are reported for the block backend, so it does not matter
that the block node structure changed with the switch to '-blockdev'.
Fixes: aaf48d8e ("command line: switch to blockdev starting with machine version 10.0")
Signed-off-by: Fiona Ebner <f.ebner at proxmox.com>
---
src/PVE/QemuServer.pm | 16 ++++++++++++++--
1 file changed, 14 insertions(+), 2 deletions(-)
diff --git a/src/PVE/QemuServer.pm b/src/PVE/QemuServer.pm
index d0c537e0..7f42256c 100644
--- a/src/PVE/QemuServer.pm
+++ b/src/PVE/QemuServer.pm
@@ -2705,8 +2705,20 @@ sub vmstatus {
$totalrdbytes = $totalrdbytes + $blockstat->{stats}->{rd_bytes};
$totalwrbytes = $totalwrbytes + $blockstat->{stats}->{wr_bytes};
- $blockstat->{device} =~ s/drive-//;
- $res->{$vmid}->{blockstat}->{ $blockstat->{device} } = $blockstat->{stats};
+ # With the switch to -blockdev, the block backend in QEMU has no name, so need to also
+ # consider the qdev ID. Note that empty CD-ROM drives do not have a node name, so that
+ # cannot be used as a fallback instead of the qdev ID.
+ my $drive_id;
+ if ($blockstat->{device}) {
+ $drive_id = $blockstat->{device} =~ s/drive-//r;
+ } elsif ($blockstat->{qdev}) {
+ $drive_id = PVE::QemuServer::Blockdev::qdev_id_to_drive_id($blockstat->{qdev});
+ } else {
+ print "blockstats callback: unexpected missing drive ID\n";
+ next;
+ }
+
+ $res->{$vmid}->{blockstat}->{$drive_id} = $blockstat->{stats};
}
$res->{$vmid}->{diskread} = $totalrdbytes;
$res->{$vmid}->{diskwrite} = $totalwrbytes;
--
2.47.2
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