From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.0 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id CF3CBC6377C for ; Mon, 19 Jul 2021 15:53:27 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 8464261400 for ; Mon, 19 Jul 2021 15:53:27 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8464261400 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:57516 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1m5VaA-0000RL-Kp for qemu-devel@archiver.kernel.org; Mon, 19 Jul 2021 11:53:26 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:53346) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1m5VZF-0007wa-7N for qemu-devel@nongnu.org; Mon, 19 Jul 2021 11:52:29 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:41640) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1m5VZB-0007Qy-LF for qemu-devel@nongnu.org; Mon, 19 Jul 2021 11:52:27 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1626709945; h=from:from:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=opqJo/oQaROxOQ4tP+4YjSba58IuzrLi4fNcxScD+QA=; b=djJRLOJkIGXFwGPgQkgEN2LgNIHkFO+wq2pZrI1WSHnDichcwqefoYzfsmhFQggeEso0Cj VIlYLu9+OLbX5WWx6bioF0djdofDXeEh1sLae6LPA05j+YmFl75/rBykJOqBe1PT0+1SPf CtsQ26+T9lZ3/ziCKyOEjOP3JeUHxP4= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-377-i2zr_LLkNDmJ8G4qsV2NdA-1; Mon, 19 Jul 2021 11:52:14 -0400 X-MC-Unique: i2zr_LLkNDmJ8G4qsV2NdA-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 4AE9E802E61; Mon, 19 Jul 2021 15:52:13 +0000 (UTC) Received: from redhat.com (ovpn-112-193.ams2.redhat.com [10.36.112.193]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 8B57B60877; Mon, 19 Jul 2021 15:52:05 +0000 (UTC) Date: Mon, 19 Jul 2021 16:52:02 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Cornelia Huck Subject: Re: [PATCH v1 1/9] s390x: smp: s390x dedicated smp parsing Message-ID: References: <1626281596-31061-1-git-send-email-pmorel@linux.ibm.com> <1626281596-31061-2-git-send-email-pmorel@linux.ibm.com> <871r7yd4gf.fsf@redhat.com> <87fswa9un2.fsf@redhat.com> MIME-Version: 1.0 In-Reply-To: <87fswa9un2.fsf@redhat.com> User-Agent: Mutt/2.0.7 (2021-05-04) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=berrange@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=216.205.24.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -42 X-Spam_score: -4.3 X-Spam_bar: ---- X-Spam_report: (-4.3 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1.469, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=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: thuth@redhat.com, ehabkost@redhat.com, Pierre Morel , david@redhat.com, richard.henderson@linaro.org, qemu-devel@nongnu.org, armbru@redhat.com, pasic@linux.ibm.com, borntraeger@de.ibm.com, qemu-s390x@nongnu.org, pbonzini@redhat.com, eblake@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Mon, Jul 19, 2021 at 05:43:29PM +0200, Cornelia Huck wrote: > (restored cc:s) > > On Fri, Jul 16 2021, Pierre Morel wrote: > > > On 7/16/21 11:14 AM, Daniel P. Berrangé wrote: > >> I increasingly worry that we're making a mistake by going down the > >> route of having custom smp_parse implementations per target, as this > >> is showing signs of inconsistent behaviour and error reportings. I > >> think the differences / restrictions have granularity at a different > >> level that is being tested in many cases too. > >> > >> Whether threads != 1 is valid will likely vary depending on what > >> CPU model is chosen, rather than what architecture is chosen. > >> The same is true for dies != 1. We're not really checking this > >> closely even in x86 - for example I can request nonsense such > >> as a 25 year old i486 CPU model with hyperthreading and multiple > >> dies > >> > >> qemu-system-x86_64 -cpu 486 -smp 16,cores=4,dies=2,threads=2 > > Now that's what I'd call an upgrade :) > > >> > >> In this patch, there is no error reporting if the user specifies > >> dies != 1 or threads != 1 - it just silently ignores the request > >> which is not good. > > > > yes, I should change this > > > >> > >> Some machine types may have constraints on CPU sockets. > >> > >> This can of course all be handled by custom smp_parse impls, but > >> this is ultimately going to lead to alot of duplicated and > >> inconsistent logic I fear. > >> > >> I wonder if we would be better off having machine class callback > >> that can report topology constraints for the current configuration, > >> along lines ofsmp_constraints(MachineState *ms, > >> > >> smp_constraints(MachineState *ms, > >> int *max_sockets, > >> int *max_dies, > >> int *max_cores, > >> int *max_threads) > > > > I find the idee good, but what about making it really machine agnostic > > by removing names and using a generic > > > > smp_constraints(MachineState *ms, > > int *nb_levels, > > int *levels[] > > ); > > > > Level can be replaced by another name like container. > > The machine could also provide the level/container names according to > > its internal documentation. > > In theory, this could give us more flexibility; however, wouldn't > that still mean that the core needs to have some knowledge of the > individual levels? We also have the command line parsing to consider, > and that one uses concrete names (which may or may not make sense, > depending on what machine you are trying to configure), and we'd still > have to map these to 'levels'. Yeah, we need to deal with names in several places, so I don't think abstracting it in one place is desirable, as it introduces the need to convert between the two and potentially obscures the semantics. 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 :|