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=-2.3 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT 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 6B35BC04AB4 for ; Tue, 14 May 2019 07:29:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 34B08208CA for ; Tue, 14 May 2019 07:29:52 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="Dzz9eun9" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726487AbfENH3u (ORCPT ); Tue, 14 May 2019 03:29:50 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:59736 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726229AbfENH3t (ORCPT ); Tue, 14 May 2019 03:29:49 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=LyILN8tiqYOrBbTwx/bEvqalqGDEJJBbWfhDeckm5hE=; b=Dzz9eun9Mdy9wxo6bjQ/SIsbt oaxyTesAJhv9qhYG29ELdIzQ8B/4GLPi0S8UY+SnAcrWsieohzt9xVLpRhitf05XQyxO7ZvDUpA0D cS8cXr+iCRBYbcZyZ7yfxlixVscm0v/7u4FMWGSfjFQof4+63mREl05GW8UbuYtl0yzm5KhC518wa 3K0+dFcGdKuj0Q3+Da79oPBpMcssZqcdi8szEOuBHxkpbs5D9EZOYRhpClyX/WmZZ7XT/F5ssJ6Il DBeWy+3TfcJ/0K1sCsfibvbpOdBb6QU26+YWbFL59jn27d7emM4RUrVU80JjsfqyYCnyCGrQaB3VT WW2asI+rg==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1hQRsd-00054W-Bb; Tue, 14 May 2019 07:29:43 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id B13822029F87A; Tue, 14 May 2019 09:29:41 +0200 (CEST) Date: Tue, 14 May 2019 09:29:41 +0200 From: Peter Zijlstra To: Liran Alon Cc: Andy Lutomirski , Alexandre Chartre , Paolo Bonzini , Radim Krcmar , Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , Dave Hansen , kvm list , X86 ML , Linux-MM , LKML , Konrad Rzeszutek Wilk , jan.setjeeilers@oracle.com, Jonathan Adams Subject: Re: [RFC KVM 00/27] KVM Address Space Isolation Message-ID: <20190514072941.GG2589@hirez.programming.kicks-ass.net> References: <1557758315-12667-1-git-send-email-alexandre.chartre@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org (please, wrap our emails at 78 chars) On Tue, May 14, 2019 at 12:08:23AM +0300, Liran Alon wrote: > 3) From (2), we should have theoretically deduced that for every > #VMExit, there is a need to kick the sibling hyperthread also outside > of guest until the #VMExit is completed. That's not in fact quite true; all you have to do is send the IPI. Having one sibling IPI the other sibling carries enough guarantees that the receiving sibling will not execute any further guest instructions. That is, you don't have to wait on the VMExit to complete; you can just IPI and get on with things. Now, this is still expensive, But it is heaps better than doing a full sync up between siblings.