Bug 1235771

Summary:	Guest should not be booted if we specify the devices we do not plan to support with -M (PCI bridge)
Product:	Red Hat Enterprise Linux 7	Reporter:	Hai Huang <hhuang>
Component:	qemu-kvm-rhev	Assignee:	Marcel Apfelbaum <marcel>
Status:	CLOSED NOTABUG	QA Contact:	Virtualization Bugs <virt-bugs>
Severity:	medium	Docs Contact:
Priority:	medium
Version:	7.2	CC:	ailan, dyuan, huding, juzhang, knoel, marcel, michen, pbonzini, virt-bugs, virt-maint, xfu
Target Milestone:	rc	Keywords:	Tracking
Target Release:	---
Hardware:	Unspecified
OS:	Unspecified
Whiteboard:
Fixed In Version:		Doc Type:	Bug Fix
Doc Text:		Story Points:	---
Clone Of:	1175215	Environment:
Last Closed:	2015-09-08 15:43:25 UTC	Type:	Bug
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:
Bug Blocks:	1175220

Description Hai Huang 2015-06-25 16:53:27 UTC

+++ This bug was initially created as a clone of Bug #1175215 +++

Description of problem:
Guest could be booted if we specify rhel7.1 new feature with -M RHEL7.0/RHEL6.x on rhel7.1 host. Consequences might have 
1. From end user pov, boot successfully means we support it, however, we do not fully support new features under older machine type.

2. https://bugzilla.redhat.com/show_bug.cgi?id=1175099 and Bug 1172643 - migration/pci-bridge: 7.1rhev->7.0 fails

Version-Release number of selected component (if applicable):
qemu-kvm-rhev-2.1.2-17.el7

How reproducible:
100%

Steps to Reproduce:
1.Boot guest with pci bridge or ovmf with -M rhel6.x on rhel7.1 host
2.
3.

Actual results:
Guest could be booted successfully but migration fail 

Expected results:
Guest should not be booted if we specify the devices we do not plan to support with -M


Additional info:

--- Additional comment from Paolo Bonzini on 2014-12-19 09:00:53 EST ---

PCI bridges were tech preview, so there's no problem in not supporting migration.  AHCI will probably be the same when we start supporting Q35 fully.

For OVMF probably the bug should not be closed, but just deferred to 7.2.  I'm reopening bug 1175099.

In any case, QE is already opening bug when they find new stuff not working on old machine types.  Changing this to a tracker.

----------------------------------------------
Cloning the BZ specifically for PCI bridge
(another BZ will be cloned for OVMF).

Comment 1 Paolo Bonzini 2015-09-08 13:22:00 UTC

The PCI bridge feature works correctly if you use the old machine type on newer host, right?

If so, this is NOTABUG (and so is the tracker bug 1175220).  When you migrate to 7.0, where the feature was tech preview, it is implied that the VM becomes unsupported.

Since it is possible to migrate 7.1-with-7.0-machine-type to another 7.1-with-7.0-machine-type, blocking migration with the 7.0 machine type would be unnecessary.  The fix (rejecting incoming migration) would have to be applied in 7.0, which is long dead.

Comment 2 Marcel Apfelbaum 2015-09-08 15:43:25 UTC

(In reply to Paolo Bonzini from comment #1)
> The PCI bridge feature works correctly if you use the old machine type on
> newer host, right?
> 
> If so, this is NOTABUG (and so is the tracker bug 1175220).  When you
> migrate to 7.0, where the feature was tech preview, it is implied that the
> VM becomes unsupported.
> 
> Since it is possible to migrate 7.1-with-7.0-machine-type to another
> 7.1-with-7.0-machine-type, blocking migration with the 7.0 machine type
> would be unnecessary.  The fix (rejecting incoming migration) would have to
> be applied in 7.0, which is long dead.

Yes, there is no reason for bridge to not work properly on older machine types.
Closed it as NOTABUG.

Thanks,
Marcel