From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 540E169D13 for ; Wed, 31 Jan 2024 10:28:53 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1706696935; cv=none; b=eHAK9IcigeuG8d/SQGQV1X9zTN42uLgNiKWjXZeupE2nN1jxeLPnFoMtmUg/ohcqO0xaZYZvgJQFpaAICF3K392oBAX6DNeLCir9kCYA1wrTgCNqFqw5VFEALF9yAU+mGkw2T+qRf6QCtkVkWSIU6GNmsSC0/Uuiw8EsZigcqy8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1706696935; c=relaxed/simple; bh=FPG6Y+PURvFGSE1B76rChV13yZ6TzykAFpFKvVJd1W4=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=nxjFznlbAn96BvRtBHnkWI+eG27QUAs+78LPypVLpbP/yezhzbi486BIBq7Dn6irOh2apjGnDkP80EJAnNidmHe/15VCqFMmqrIK2NCHU/LK5Am3urYkeqNl/LipR+cIwDaVuxjIkqYJFd7SCl0yVuJ5fVDP/4SpdA27SLWljb4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=NBdJIzfJ; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="NBdJIzfJ" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1706696932; 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:in-reply-to:in-reply-to: references:references; bh=7QFSz4iLpWcX1LVK89RhT/r6+WUAlS1/Pj27Dogjyms=; b=NBdJIzfJlP6KX/rzU1J3ZVV+4XxVG42VRpTFl5SBbRqq9njNdYlTqiNmLJFk+df3IqMifr 5Q/na0iDVfAOGT5CWiHLo53r1Nhjk18wt+iMnMnYMj/7XzyaWEHZIB/D4oMKrFM2Gf7waC cYx65CeCeLmXRmQacDqdauQXuyPA0Xs= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-524-ncC9b_gUPgOcqtOek-qlUw-1; Wed, 31 Jan 2024 05:28:48 -0500 X-MC-Unique: ncC9b_gUPgOcqtOek-qlUw-1 Received: from smtp.corp.redhat.com (int-mx09.intmail.prod.int.rdu2.redhat.com [10.11.54.9]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 73D3C8B3963; Wed, 31 Jan 2024 10:28:47 +0000 (UTC) Received: from redhat.com (unknown [10.42.28.72]) by smtp.corp.redhat.com (Postfix) with ESMTPS id D7551492BC6; Wed, 31 Jan 2024 10:28:44 +0000 (UTC) Date: Wed, 31 Jan 2024 10:28:42 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Zhao Liu Cc: Eduardo Habkost , Marcel Apfelbaum , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= , Yanan Wang , "Michael S . Tsirkin" , Paolo Bonzini , Richard Henderson , Eric Blake , Markus Armbruster , Marcelo Tosatti , qemu-devel@nongnu.org, kvm@vger.kernel.org, Babu Moger , Xiaoyao Li , Zhenyu Wang , Zhuocheng Ding , Yongwei Ma , Zhao Liu Subject: Re: [PATCH v8 00/21] Introduce smp.modules for x86 in QEMU Message-ID: Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= References: <20240131101350.109512-1-zhao1.liu@linux.intel.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20240131101350.109512-1-zhao1.liu@linux.intel.com> User-Agent: Mutt/2.2.12 (2023-09-09) X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.9 On Wed, Jan 31, 2024 at 06:13:29PM +0800, Zhao Liu wrote: > From: Zhao Liu > > Hi list, > > This is the our v8 patch series, rebased on the master branch at the > commit 11be70677c70 ("Merge tag 'pull-vfio-20240129' of > https://github.com/legoater/qemu into staging"). > > Compared with v7 [1], v8 mainly has the following changes: > * Introduced smp.modules for x86 instead of reusing current > smp.clusters. > * Reworte the CPUID[0x1F] encoding. > > Given the code change, I dropped the most previously gotten tags > (Acked-by/Reviewed-by/Tested-by from Michael & Babu, thanks for your > previous reviews and tests!) in v8. > > With the description of the new modules added to x86 arch code in v7 [1] > cover letter, the following sections are mainly the description of > the newly added smp.modules (since v8) as supplement. > > Welcome your comments! > > > Why We Need a New CPU Topology Level > ==================================== > > For the discussion in v7 about whether we should reuse current > smp.clusters for x86 module, the core point is what's the essential > differences between x86 module and general cluster. > > Since, cluster (for ARM/riscv) lacks a comprehensive and rigorous > hardware definition, and judging from the description of smp.clusters > [2] when it was introduced by QEMU, x86 module is very similar to > general smp.clusters: they are all a layer above existing core level > to organize the physical cores and share L2 cache. > > However, after digging deeper into the description and use cases of > cluster in the device tree [3], I realized that the essential > difference between clusters and modules is that cluster is an extremely > abstract concept: > * Cluster supports nesting though currently QEMU doesn't support > nested cluster topology. However, modules will not support nesting. > * Also due to nesting, there is great flexibility in sharing resources > on clusters, rather than narrowing cluster down to sharing L2 (and > L3 tags) as the lowest topology level that contains cores. > * Flexible nesting of cluster allows it to correspond to any level > between the x86 package and core. > > Based on the above considerations, and in order to eliminate the naming > confusion caused by the mapping between general cluster and x86 module > in v7, we now formally introduce smp.modules as the new topology level. What is the Linux kernel calling this topology level on x86 ? It will be pretty unfortunate if Linux and QEMU end up with different names for the same topology level. With 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 :|