On Mon, Jul 20, 2020 at 12:22:33PM +0200, Thomas Huth wrote:
qemuAgentFSInfoToPublic() currently only sets the devAlias for PCI
devices.
However, the QEMU guest agent could also provide the device name in the
"dev" field of the response for other devices instead (well, at least after
fixing another problem in the current QEMU guest agent...). So if creating
the devAlias from the PCI information failed, let's fall back to the name
provided by the guest agent. This helps to fix the empty "Target" fields
that occur when running "virsh domfsinfo" on s390x where CCW devices are
used for the guest instead of PCI devices.
Also add a proper debug message here in case we completely failed to set the
device alias, since this problem here was very hard to debug: The only two
error messages that I've seen were "Unable to get filesystem information"
and "Unable to encode message payload" - which only indicates that something
went wrong in the RPC call. No debug message indicated the real problem, so
I had to learn the hard way why the RPC call failed (it apparently does not
like devAlias left to be NULL) and where the real problem comes from.
Buglink:
https://bugzilla.redhat.com/show_bug.cgi?id=1755075
Signed-off-by: Thomas Huth <thuth(a)redhat.com>
---
src/qemu/qemu_driver.c | 19 +++++++++++--------
1 file changed, 11 insertions(+), 8 deletions(-)
diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index d185666ed8..e45c61ee20 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -21935,14 +21935,17 @@ qemuAgentFSInfoToPublic(qemuAgentFSInfoPtr agent,
qemuAgentDiskInfoPtr agentdisk = agent->disks[i];
virDomainDiskDefPtr diskDef;
- if (!(diskDef = virDomainDiskByAddress(vmdef,
- &agentdisk->pci_controller,
- agentdisk->bus,
- agentdisk->target,
- agentdisk->unit)))
- continue;
-
- ret->devAlias[i] = g_strdup(diskDef->dst);
+ diskDef = virDomainDiskByAddress(vmdef,
+ &agentdisk->pci_controller,
+ agentdisk->bus,
+ agentdisk->target,
+ agentdisk->unit);
Hmmm, even on x86 I think the original code is broken, or at least fragile.
The libvirt "bus" number is not guaranteed to match the guest kernel PCI
"bus" number. I wonder if this has been validated for complex PCI-Express
topologies.
+ if (diskDef != NULL)
+ ret->devAlias[i] = g_strdup(diskDef->dst);
+ else if (agentdisk->devnode != NULL)
+ ret->devAlias[i] = g_strdup(agentdisk->devnode);
In the linked BZ the "devnode" field is not provided either. You mention
a related QEMU patch, which I guess fixes that issue in QEMU ? Can you point
to that fix.
+ else
+ VIR_DEBUG("Missing devnode name for '%s'.",
ret->mountpoint);
}
Regards,
Daniel
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