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=-0.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable 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 6E451C31E4B for ; Fri, 14 Jun 2019 21:44:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4E5DA2183F for ; Fri, 14 Jun 2019 21:44:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726327AbfFNVok (ORCPT ); Fri, 14 Jun 2019 17:44:40 -0400 Received: from mail-wr1-f66.google.com ([209.85.221.66]:41583 "EHLO mail-wr1-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726073AbfFNVok (ORCPT ); Fri, 14 Jun 2019 17:44:40 -0400 Received: by mail-wr1-f66.google.com with SMTP id c2so3946903wrm.8 for ; Fri, 14 Jun 2019 14:44:38 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:in-reply-to:references:date :message-id:mime-version; bh=Ld3jYaYOalugs6NakkhvxfE6gQQVFoIIwwhNaKu9MOs=; b=m74IXzbLYCt9n5AFyI3yPS4CSIGGfcLABXnNFDcZKCD3i3kvi1U940PSIF18gx0lWO 4j9J6/fUdsqX8s1jQAgnc/JJXBdpa2x680aus9Y17F7wnQ7tEm0223D4aMUuljv3BvL1 Ce+VbZGHrgGz+VNBFUCnnCvZhZSs5Myu6/TMhVzgJuXUCG4AjiH/Is0IgPoLyVvebemM SKNtSfL+CJ0fCJOfBRuyT7Crtk0QzkaiJ5w1iNHliX+a4eACBIO3Obe+4xtqe5qd+pUy yCfRbYJ/ZjRWNp+p5r0T+4rTUYE3g0uCvANMtL8/GfIHEEukqPjOt3GflcypLWLBajp7 BPNA== X-Gm-Message-State: APjAAAUl+dD03vvGlCaEsmOYZ74SkC+GXM1rvcX/apArUWtfY0GOab9D zH4rtiTmFyJe8ZkEabzAD0dSog== X-Google-Smtp-Source: APXvYqwtUzuPcck2AHyIXDAtw0zg3eNPDxrY9SB60wA2LaOW4/UoaSEnBo/i0WOqLauPH2dS3zi6EA== X-Received: by 2002:a5d:4a0e:: with SMTP id m14mr19268175wrq.91.1560548678052; Fri, 14 Jun 2019 14:44:38 -0700 (PDT) Received: from vitty.brq.redhat.com (ip-78-102-201-117.net.upcbroadband.cz. [78.102.201.117]) by smtp.gmail.com with ESMTPSA id h23sm2938104wmb.25.2019.06.14.14.44.36 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Fri, 14 Jun 2019 14:44:37 -0700 (PDT) From: Vitaly Kuznetsov To: Peter Zijlstra Cc: linux-kernel@vger.kernel.org, Prasanna Panchamukhi , Andy Lutomirski , Borislav Petkov , Cathy Avery , Haiyang Zhang , "H. Peter Anvin" , Ingo Molnar , "K. Y. Srinivasan" , "Michael Kelley \(EOSG\)" , Mohammed Gamal , Paolo Bonzini , Radim =?utf-8?B?S3LEjW3DocWZ?= , Roman Kagan , Sasha Levin , Stephen Hemminger , Thomas Gleixner , devel@linuxdriverproject.org, kvm@vger.kernel.org, linux-hyperv@vger.kernel.org, x86@kernel.org, Dmitry Safonov Subject: Re: [PATCH] x86/hyperv: Disable preemption while setting reenlightenment vector In-Reply-To: <20190614122726.GL3436@hirez.programming.kicks-ass.net> References: <20190611212003.26382-1-dima@arista.com> <8736kff6q3.fsf@vitty.brq.redhat.com> <20190614082807.GV3436@hirez.programming.kicks-ass.net> <877e9o7a4e.fsf@vitty.brq.redhat.com> <20190614122726.GL3436@hirez.programming.kicks-ass.net> Date: Fri, 14 Jun 2019 23:44:36 +0200 Message-ID: <87pnnf6dvf.fsf@vitty.brq.redhat.com> MIME-Version: 1.0 Content-Type: text/plain Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Peter Zijlstra writes: > > I know you probably can't change the HV interface, but I'm thinking its > rather daft you have to specify a CPU at all for this. The HV can just > pick one and send the notification there, who cares. Generally speaking, hypervisor can't know if the CPU is offline (or e.g. 'isolated') from guest's perspective so I think having an option to specify affinity for reenlightenment notification is rather a good thing, not bad. (Actually, I don't remember if I tried specifying 'HV_ANY' (U32_MAX-1) here to see what happens. But then I doubt it'll notice the fact that we offlined some CPU so we may get a totally unexpected IRQ there). -- Vitaly