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=-3.9 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS 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 91806C433DF for ; Fri, 21 Aug 2020 09:48:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 54FEC20732 for ; Fri, 21 Aug 2020 09:48:10 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=alien8.de header.i=@alien8.de header.b="ST2YWj2u" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728338AbgHUJsJ (ORCPT ); Fri, 21 Aug 2020 05:48:09 -0400 Received: from mail.skyhub.de ([5.9.137.197]:46518 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725855AbgHUJsI (ORCPT ); Fri, 21 Aug 2020 05:48:08 -0400 Received: from zn.tnic (p200300ec2f0eda003935e3317bb76801.dip0.t-ipconnect.de [IPv6:2003:ec:2f0e:da00:3935:e331:7bb7:6801]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.skyhub.de (SuperMail on ZX Spectrum 128k) with ESMTPSA id 14D811EC0426; Fri, 21 Aug 2020 11:48:07 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=alien8.de; s=dkim; t=1598003287; h=from:from: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:in-reply-to:in-reply-to: references:references; bh=+0ENpjcxM2Qzt/z2kna3FCQDeW7bODLheZkT+Orfjyg=; b=ST2YWj2ug/4JGtnMQFlZSPIpI32BMCI53zPMNw8B+fFl5SPgUiQjHqCgvVbLnzKWN6QBCx Onh0koE2gmQbHnb5Uh336pkz0rYlTKoHiqwCXurxSdhqM3FL23XjHTYpTA8fq7eYQ3fyZV 32bs+y2NX4gliBfKZQwKMcf3n5fGX08= Date: Fri, 21 Aug 2020 11:48:02 +0200 From: Borislav Petkov To: Paolo Bonzini Cc: Sean Christopherson , Andy Lutomirski , Thomas Gleixner , Ingo Molnar , x86@kernel.org, "H. Peter Anvin" , linux-kernel@vger.kernel.org, Dave Hansen , Chang Seok Bae , Peter Zijlstra , Sasha Levin , kvm@vger.kernel.org, Tom Lendacky Subject: Re: [PATCH] x86/entry/64: Disallow RDPID in paranoid entry if KVM is enabled Message-ID: <20200821094802.GG12181@zn.tnic> References: <20200821025050.32573-1-sean.j.christopherson@intel.com> <20200821074743.GB12181@zn.tnic> <3eb94913-662d-5423-21b1-eaf75635142a@redhat.com> <20200821081633.GD12181@zn.tnic> <3b4ba9e9-dbf6-a094-0684-e68248050758@redhat.com> <20200821092237.GF12181@zn.tnic> <1442e559-dde4-70f6-85ac-58109cf81c16@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <1442e559-dde4-70f6-85ac-58109cf81c16@redhat.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Aug 21, 2020 at 11:44:33AM +0200, Paolo Bonzini wrote: > It's not like we grab MSRs every day. The user-return notifier restores > 6 MSRs (7 on very old processors). The last two that were added were > MSR_TSC_AUX itself in 2009 (!) and MSR_IA32_TSX_CTRL last year. What about "If it is a shared resource, there better be an agreement about sharing it." is not clear? It doesn't matter how many or which resources - there needs to be a contract for shared use so that shared use is possible. It is that simple. -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette