Bug 1227354
| Summary: | [virtio-1] Disabling Virtio-1 from Libvirt | ||
|---|---|---|---|
| Product: | Red Hat Enterprise Linux 7 | Reporter: | Amnon Ilan <ailan> |
| Component: | libvirt | Assignee: | Ján Tomko <jtomko> |
| Status: | CLOSED DEFERRED | QA Contact: | Han Han <hhan> |
| Severity: | unspecified | Docs Contact: | |
| Priority: | unspecified | ||
| Version: | 7.2 | CC: | ailan, berrange, dyuan, dzheng, gsun, hhan, jsuchane, juzhang, laine, lmen, mzhan, qzhang, rbalakri, sherold, vincent.jardin, xuzhang, yanyang |
| Target Milestone: | rc | Keywords: | FutureFeature |
| Target Release: | --- | ||
| Hardware: | Unspecified | ||
| OS: | Unspecified | ||
| Whiteboard: | |||
| Fixed In Version: | Doc Type: | Enhancement | |
| Doc Text: | Story Points: | --- | |
| Clone Of: | Environment: | ||
| Last Closed: | 2017-05-22 17:38:33 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: | 1227343 | ||
| Bug Blocks: | 1288337, 1365823 | ||
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Description
Amnon Ilan
2015-06-02 13:18:22 UTC
(In reply to Amnon Ilan from comment #0) > Description of problem: > > Control 'disable-modern' and 'disable-legacy' flags for all virtio devices > Required in order to avoid compatibility issues. What compatibility issues ? IIUC, QEMU ought to negotiate the right settings for virtio with the guest OS. Adding these flags to libvirt XML for guests seems like quite a unpleasant thing to do. In 7.3 the default Virtio mode will be "transitional": both legacy and modern are enabled. Since "modern" (Virtio 1) is new, there may be some issues that will not be discovered by QE. In such a case we can run into problems if we have no way to force the driver to "legacy" mode. That is why 'disable-modern' is important. Now for the imprtance of 'disable-legacy' (less important, but yet): when we wish to boot from a virtio device and the device is in legacy mode, the device will require io space, and this space is very limited (as an example, see: https://bugzilla.redhat.com/show_bug.cgi?id=1175124 ). In such cases we would like to do 'disable-legacy' since Virtio 1 does not require the io space. Both cases are related to customer usage and not only testing (where qemu command-line could do the job). Proposed upstream patches: https://www.redhat.com/archives/libvir-list/2016-July/msg01235.html The upstream design is still not settled: https://www.redhat.com/archives/libvir-list/2016-September/msg00228.html Per: https://www.redhat.com/archives/libvir-list/2016-September/msg00227.html it would be nicer not to expose this in the XML unless really needed. |