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Wed, 26 Aug 2020 12:51:02 +0000 (UTC) Date: Wed, 26 Aug 2020 13:50:59 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Igor Mammedov Subject: Re: [PATCH v5 0/8] Remove EPYC mode apicid decode and use generic decode Message-ID: <20200826125059.GN168515@redhat.com> References: <159804762216.39954.15502128500494116468.stgit@naples-babu.amd.com> <20200826143849.59f6970b@redhat.com> MIME-Version: 1.0 In-Reply-To: <20200826143849.59f6970b@redhat.com> User-Agent: Mutt/1.14.6 (2020-07-11) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=berrange@redhat.com X-Mimecast-Spam-Score: 0.001 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Received-SPF: pass client-ip=205.139.110.61; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/08/26 06:53:09 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -30 X-Spam_score: -3.1 X-Spam_bar: --- X-Spam_report: (-3.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.959, 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_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, 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: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Cc: ehabkost@redhat.com, mst@redhat.com, Michal Privoznik , qemu-devel@nongnu.org, Babu Moger , pbonzini@redhat.com, rth@twiddle.net Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Wed, Aug 26, 2020 at 02:38:49PM +0200, Igor Mammedov wrote: > On Fri, 21 Aug 2020 17:12:19 -0500 > Babu Moger wrote: > > > To support some of the complex topology, we introduced EPYC mode apicid decode. > > But, EPYC mode decode is running into problems. Also it can become quite a > > maintenance problem in the future. So, it was decided to remove that code and > > use the generic decode which works for majority of the topology. Most of the > > SPECed configuration would work just fine. With some non-SPECed user inputs, > > it will create some sub-optimal configuration. > > Here is the discussion thread. > > https://lore.kernel.org/qemu-devel/c0bcc1a6-1d84-a6e7-e468-d5b437c1b254@amd.com/ > > > > This series removes all the EPYC mode specific apicid changes and use the generic > > apicid decode. > > the main difference between EPYC and all other CPUs is that > it requires numa configuration (it's not optional) > so we need an extra patch on top of this series to enfoce that, i.e: > > if (epyc && !numa) > error("EPYC cpu requires numa to be configured") Please no. This will break 90% of current usage of the EPYC CPU in real world QEMU deployments. That is way too user hostile to introduce as a requirement. Why do we need to force this ? People have been successfuly using EPYC CPUs without NUMA in QEMU for years now. It might not match behaviour of bare metal silicon, but that hasn't obviously caused the world to come crashing down. Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|