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Thu, 20 Aug 2020 16:51:03 +0000 (UTC) Date: Thu, 20 Aug 2020 12:51:03 -0400 From: Eduardo Habkost To: David Gibson Subject: Re: [PATCH 02/10] numa: introduce MachineClass::forbid_asymmetrical_numa Message-ID: <20200820165103.GD642093@habkost.net> References: <20200814205424.543857-1-danielhb413@gmail.com> <20200814205424.543857-3-danielhb413@gmail.com> <20200820011726.GF271315@yekko.fritz.box> <20200820021128.GC642093@habkost.net> <20200820041504.GN271315@yekko.fritz.box> MIME-Version: 1.0 In-Reply-To: <20200820041504.GN271315@yekko.fritz.box> X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=ehabkost@redhat.com X-Mimecast-Spam-Score: 0.002 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Received-SPF: pass client-ip=207.211.31.81; envelope-from=ehabkost@redhat.com; helo=us-smtp-delivery-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/08/19 20:12:44 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -40 X-Spam_score: -4.1 X-Spam_bar: ---- X-Spam_report: (-4.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-1, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: John Snow , Daniel Henrique Barboza , qemu-ppc@nongnu.org, qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Thu, Aug 20, 2020 at 02:15:04PM +1000, David Gibson wrote: > On Wed, Aug 19, 2020 at 10:11:28PM -0400, Eduardo Habkost wrote: > > On Thu, Aug 20, 2020 at 11:17:26AM +1000, David Gibson wrote: > > > On Fri, Aug 14, 2020 at 05:54:16PM -0300, Daniel Henrique Barboza wrote: > > > > The pSeries machine does not support asymmetrical NUMA > > > > configurations. > > > > > > This seems a bit oddly specific to have as a global machine class > > > property. > > > > > > Would it make more sense for machines with specific NUMA constraints > > > to just verify those during their initialization? > > > > This would be much simpler. However, I like the idea of > > representing machine-specific configuration validation rules as > > data that can eventually be exported to management software. > > Ah, ok, so basically the usual tradeoff between flexibility and > advertisability. > > So, in that case, I guess the question is whether we envisage "no > assymmetry" as a constraint common enough that it's worth creating an > advertisable rule or not. If we only ever have one user, then we > haven't really done any better than hard coding the constraint in the > manageent software. > > Of course to complicate matters, in the longer term we're looking at > removing that constraint from pseries - but doing so will be dependent > on the guest kernel understanding a new format for the NUMA > information in the device tree. So qemu alone won't have enough > information to tell if such a configuration is possible or not. Requiring both QEMU (and possibly management software) to be patched again after the guest kernel is fixed sounds undesirable. Perhaps a warning would be better in this case? In either case, it sounds like this won't be a common constraint and I now agree with your original suggestion of doing this in machine initialization code. -- Eduardo