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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D35F5C4332F for ; Mon, 14 Nov 2022 20:49:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235836AbiKNUtQ (ORCPT ); Mon, 14 Nov 2022 15:49:16 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60602 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229484AbiKNUtP (ORCPT ); Mon, 14 Nov 2022 15:49:15 -0500 Received: from mail-pl1-x633.google.com (mail-pl1-x633.google.com [IPv6:2607:f8b0:4864:20::633]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BE34914D2B for ; Mon, 14 Nov 2022 12:49:14 -0800 (PST) Received: by mail-pl1-x633.google.com with SMTP id j12so11205764plj.5 for ; Mon, 14 Nov 2022 12:49:14 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=gkgjefB1+6KbyMu0uuZ086tg7a8inwZvw55s87p+Sl8=; b=R2VcHAQWKWoSy4Ex1PFK4F3oamdO5rj1n4O638YozO3My7kwm1gCGnmnzN36/1/33q M748CRiXx4GbKbhsi2m9V54akbITPAKUw8XuAx/JCyOtHTOels+9fKThsDYLCslHkNwa +ehxiQOJ8RAnW9A1nb3Bk+FBnAfTcEmje3wFwqXwuflaSsZegBhb0+ChHR9qo+mweJO0 TTwJDB6JySiBnton9O55nP66yKkloLmeGdStBtpmHt5kXS3ueRP/K3gVxDTt/g6y7nuh kMT/csMSQObsM5p7RXAVAUet3euhxmUZslozcZVpOJPoCHCkmpa5y3v+jFZswfXHOq21 oVQg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=gkgjefB1+6KbyMu0uuZ086tg7a8inwZvw55s87p+Sl8=; b=grOaHo1yY/+pYMtUpShOjiDIgWRezGUZCPwlXGlWGhvwFr5o8w82POfKiqfqhb5FMO ZU6eOjVxLk+6AZCpiKSeyM3cU0lkPBSDyokWcKf/Oik4E26xrGAlnIi76yjhz90h7Xf2 j3c2c+ZbvFg9ynBeCKhQlwhLffj8LJkVzChaX/wDgb/MPhetlKkeBanGcMf8meF7yIZ0 CDLFX5QD00V+GHYmfBTYMhtmPIzN9aVsSUssuqWurKlNEVCOJzt2DPrF91sxar4h3CvE zILF6xwhb3MQhPslYAF0lDsGBEedEd0MoE4SVtrn2jaFYoedcZbrr83aGk5kR/9yZ2sA xnug== X-Gm-Message-State: ANoB5pkj48H6DOFocrO5gPkVpsvBM96DxsOz1OzBvhxFeplS8bPndiyy oyC5ycXlYWj+K2u0i1R37/Dx0w== X-Google-Smtp-Source: AA0mqf4QfkDuhsj6MXKqI+aIdHahZZ03Y/CtArwCpMRQUe+J2W/5u2HBqoHFVITNxUGEwp/FQbRjow== X-Received: by 2002:a17:90a:617:b0:213:cb87:8cd4 with SMTP id j23-20020a17090a061700b00213cb878cd4mr15433263pjj.78.1668458954145; Mon, 14 Nov 2022 12:49:14 -0800 (PST) Received: from google.com (7.104.168.34.bc.googleusercontent.com. [34.168.104.7]) by smtp.gmail.com with ESMTPSA id i24-20020aa796f8000000b00562784609fbsm7129596pfq.209.2022.11.14.12.49.12 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 14 Nov 2022 12:49:13 -0800 (PST) Date: Mon, 14 Nov 2022 20:49:09 +0000 From: Sean Christopherson To: Mathieu Desnoyers Cc: Andy Lutomirski , Peter Zijlstra , linux-kernel@vger.kernel.org, Thomas Gleixner , "Paul E . McKenney" , Boqun Feng , "H . Peter Anvin" , Paul Turner , linux-api@vger.kernel.org, Christian Brauner , Florian Weimer , David.Laight@aculab.com, carlos@redhat.com, Peter Oskolkov , Alexander Mikhalitsyn , Chris Kennelly Subject: Re: [PATCH v5 08/24] sched: Introduce per memory space current virtual cpu id Message-ID: References: <20221103200359.328736-1-mathieu.desnoyers@efficios.com> <20221103200359.328736-9-mathieu.desnoyers@efficios.com> <2f191ddb-de89-52c0-e7da-26ac0239b8fe@efficios.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <2f191ddb-de89-52c0-e7da-26ac0239b8fe@efficios.com> Precedence: bulk List-ID: X-Mailing-List: linux-api@vger.kernel.org On Fri, Nov 11, 2022, Mathieu Desnoyers wrote: > On 2022-11-10 23:41, Andy Lutomirski wrote: > > On Thu, Nov 3, 2022 at 1:05 PM Mathieu Desnoyers > > wrote: > > Also, in my mind "virtual cpu" is vCPU, which this isn't. Maybe > > "compacted cpu" or something? It's a strange sort of concept. > > I've kept the same wording that has been introduced in 2011 by Paul Turner > and used internally at Google since then, although it may be confusing if > people expect kvm-vCPU and rseq-vcpu to mean the same thing. Both really end > up providing the semantic of a virtually assigned cpu id (in opposition to > the logical cpu id on the system), but this is much more involved in the > case of KVM. I had the same reaction as Andy. The rseq concepts don't worry me so much as the existence of "vcpu" in mm_struct/task_struct, e.g. switch_mm_vcpu() when switching between KVM vCPU tasks is going to be super confusing. Ditto for mm_vcpu_get() and mm_vcpu_put() in the few cases where KVM currently does mmget()/mmput().