Bug 1579691 – [Deployment][RHOSP-13] Lift the restriction on choices for `cpu_model_extra_flags` config attribute

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Bug 1579691 - [Deployment][RHOSP-13] Lift the restriction on choices for `cpu_model_extra_flags` config attribute

Summary:	[Deployment][RHOSP-13] Lift the restriction on choices for `cpu_model_extra_f...

Status:	CLOSED ERRATA

Aliases:	None

Product:	Red Hat OpenStack
Classification:	Red Hat
Component:	puppet-nova (Show other bugs)
Sub Component:
Version:	13.0 (Queens)
Hardware:	Unspecified Unspecified

Priority	medium Severity medium
Target Milestone:	z2
Target Release:	13.0 (Queens)
Assigned To:	Rajesh Tailor
QA Contact:	nova-maint
Docs Contact:

URL:
Whiteboard:
Keywords:	Triaged, ZStream

Depends On:	1579681 1579699
Blocks:	1579693 1579694
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Reported:	2018-05-18 03:07 EDT by Rajesh Tailor
Modified:	2018-08-29 12:37 EDT (History)
CC List:	9 users (show)

See Also:
Fixed In Version:	puppet-nova-12.4.0-6.el7ost
Doc Type:	Enhancement
Doc Text:	Nova's libvirt driver now allows the specification of granular CPU feature flags when configuring CPU models. One benefit of this is the alleviation of a performance degradation experienced on guests running with certain Intel-based virtual CPU models after application of the "Meltdown" CVE fixes. This guest performance impact is reduced by exposing the CPU feature flag 'PCID' ("Process-Context ID") to the guest CPU, assuming that the PCID flag is available in the physical hardware itself. This change removes the restriction of having only 'PCID' as the only CPU feature flag and allows for the addition and removal of multiple CPU flags, making way for other use cases. For more information, refer to the documentation of ``[libvirt]/cpu_model_extra_flags`` in ``nova.conf``.
Story Points:	---
Clone Of:	1579681
Clones:	1579693 (view as bug list)
Environment:
Last Closed:	2018-08-29 12:36:37 EDT
Type:	Bug
Regression:	---
Mount Type:	---
Documentation:	---
CRM:
Verified Versions:
Category:	---
oVirt Team:	---
RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---

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External Trackers
Tracker	ID	Priority	Status	Summary	Last Updated
Red Hat Product Errata	RHBA-2018:2574	None	None	None	2018-08-29 12:37 EDT

Groups: None (edit)

Description Rajesh Tailor 2018-05-18 03:07:51 EDT

+++ This bug was initially created as a clone of Bug #1579681 +++

(This bug is a follow-up item to the:
https://bugzilla.redhat.com/show_bug.cgi?id=1547954 -- Deployment RFE: add ability to configure extra CPU flags for named CPU models)

This introduced the Nova configuration attribute
`[libvirt]/cpu_model_extra_flags`, we have restricted the choices to be
only 'PCID' -- to alleviate the immediate guest performance degradation
as a result of applying the "Meltdown" CVE fixes.

Now remove that restriction to allow adding and removing multiple CPU
flags, making way for other use cases.

Use cases:

  - Ability to use 1GB huge pages with Haswell model as one use case for
    extra flags:

        cpu_model=Haswell-noTSX-IBRS 
        cpu_model_extra_flags="pdpe1gb"

  - Nested Virtualization -- an operator can specify the Intel 'vmx' or
    AMD 'svm' flags in the level-1 Nova guest.

Comment 13 Joanne O'Flynn 2018-08-15 04:05:56 EDT

This bug is marked for inclusion in the errata but does not currently contain draft documentation text. To ensure the timely release of this advisory please provide draft documentation text for this bug as soon as possible.

If you do not think this bug requires errata documentation, set the requires_doc_text flag to "-".


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Comment 15 errata-xmlrpc 2018-08-29 12:36:37 EDT

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHBA-2018:2574

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