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=-2.4 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 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 D1982C43141 for ; Thu, 14 Nov 2019 05:08:34 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 587F9205C9 for ; Thu, 14 Nov 2019 05:08:34 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=ozlabs.org header.i=@ozlabs.org header.b="A85mzLCe" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 587F9205C9 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=ozlabs.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 9D2426B0003; Thu, 14 Nov 2019 00:08:33 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 983C26B0005; Thu, 14 Nov 2019 00:08:33 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 872E36B0006; Thu, 14 Nov 2019 00:08:33 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0211.hostedemail.com [216.40.44.211]) by kanga.kvack.org (Postfix) with ESMTP id 72E5E6B0003 for ; Thu, 14 Nov 2019 00:08:33 -0500 (EST) Received: from smtpin12.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with SMTP id 0534E181AEF1A for ; Thu, 14 Nov 2019 05:08:33 +0000 (UTC) X-FDA: 76153702506.12.chain79_104fee5f1a72f X-HE-Tag: chain79_104fee5f1a72f X-Filterd-Recvd-Size: 4682 Received: from ozlabs.org (bilbo.ozlabs.org [203.11.71.1]) by imf47.hostedemail.com (Postfix) with ESMTP for ; Thu, 14 Nov 2019 05:08:31 +0000 (UTC) Received: by ozlabs.org (Postfix, from userid 1003) id 47D8dR40m4z9s7T; Thu, 14 Nov 2019 16:08:27 +1100 (AEDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ozlabs.org; s=201707; t=1573708107; bh=kPRYQtgfmwdv40EbuZcqeYZToO/RlWVUa8XfGajWvEI=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=A85mzLCe/m8AOIXYfoAJDqpK70LNQTu2NI6GpcGjIrL25sgnKF4HZRCR3kxRgBTf0 G172C2juWrJytAFkuaI+uojelB+dtpIJod2mwqc6bXxz5pU2EbAwmg0m4QNXU2clFC RDi0G4X+NjFnbjSk0g0YYXLGkjQDO1DMhXRKTSKGoPtCi+ueh2/hkbx+89sDFfLkZ6 HDL8rgIVAUeLPPowCl2fFbLv/u6yq0hhN57mTIl+TYgTxH3zcFaVwGlCWdBMs1vjn9 PfySVcQ910QyGD55HBHYIqO6ldJ2Nk64IK6NM/MF46bZWK22t6sZrm8aU2Q9l2vR2y xs13pE6bm/PlA== Date: Thu, 14 Nov 2019 16:08:25 +1100 From: Paul Mackerras To: Ram Pai Cc: Bharata B Rao , linuxppc-dev@lists.ozlabs.org, kvm-ppc@vger.kernel.org, linux-mm@kvack.org, paulus@au1.ibm.com, aneesh.kumar@linux.vnet.ibm.com, jglisse@redhat.com, cclaudio@linux.ibm.com, sukadev@linux.vnet.ibm.com, hch@lst.de, Sukadev Bhattiprolu , Ram Pai Subject: Re: [PATCH v10 7/8] KVM: PPC: Implement H_SVM_INIT_ABORT hcall Message-ID: <20191114050825.GB28382@oak.ozlabs.ibm.com> References: <20191111041924.GA4017@oak.ozlabs.ibm.com> <20191112010158.GB5159@oc0525413822.ibm.com> <20191112053836.GB10885@oak.ozlabs.ibm.com> <20191112075215.GD5159@oc0525413822.ibm.com> <20191112113204.GA10178@blackberry> <20191112144555.GE5159@oc0525413822.ibm.com> <20191113001427.GA17829@oak.ozlabs.ibm.com> <20191113063233.GF5159@oc0525413822.ibm.com> <20191113211824.GA20535@blackberry> <20191113215042.GG5159@oc0525413822.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191113215042.GG5159@oc0525413822.ibm.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000001, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, Nov 13, 2019 at 01:50:42PM -0800, Ram Pai wrote: > On Thu, Nov 14, 2019 at 08:18:24AM +1100, Paul Mackerras wrote: > > On Tue, Nov 12, 2019 at 10:32:33PM -0800, Ram Pai wrote: > > > On Wed, Nov 13, 2019 at 11:14:27AM +1100, Paul Mackerras wrote: > > > > On Tue, Nov 12, 2019 at 06:45:55AM -0800, Ram Pai wrote: > > > > > On Tue, Nov 12, 2019 at 10:32:04PM +1100, Paul Mackerras wrote: > > > > > > On Mon, Nov 11, 2019 at 11:52:15PM -0800, Ram Pai wrote: > > > > > > > There is subtle problem removing that code from the assembly. > > > > > > > > > > > > > > If the H_SVM_INIT_ABORT hcall returns to the ultravisor without clearing > > > > > > > kvm->arch.secure_guest, the hypervisor will continue to think that the > > > > > > > VM is a secure VM. However the primary reason the H_SVM_INIT_ABORT > > > > > > > hcall was invoked, was to inform the Hypervisor that it should no longer > > > > > > > consider the VM as a Secure VM. So there is a inconsistency there. > > > > > > > > > > > > Most of the checks that look at whether a VM is a secure VM use code > > > > > > like "if (kvm->arch.secure_guest & KVMPPC_SECURE_INIT_DONE)". Now > > > > > > since KVMPPC_SECURE_INIT_ABORT is 4, an if statement such as that will > > > > > > take the false branch once we have set kvm->arch.secure_guest to > > > > > > KVMPPC_SECURE_INIT_ABORT in kvmppc_h_svm_init_abort. So in fact in > > > > > > most places we will treat the VM as a normal VM from then on. If > > > > > > there are any places where we still need to treat the VM as a secure > > > > > > VM while we are processing the abort we can easily do that too. > > > > > > > > > > Is the suggestion -- KVMPPC_SECURE_INIT_ABORT should never return back > > > > > to the Ultravisor? Because removing that assembly code will NOT lead the > > > > > > > > No. The suggestion is that vcpu->arch.secure_guest stays set to > > > > KVMPPC_SECURE_INIT_ABORT until userspace calls KVM_PPC_SVM_OFF. > > > > > > In the fast_guest_return path, if it finds > > > (kvm->arch.secure_guest & KVMPPC_SECURE_INIT_ABORT) is true, should it return to > > > UV or not? > > > > > > Ideally it should return back to the ultravisor the first time > > > KVMPPC_SECURE_INIT_ABORT is set, and not than onwards. > > > > What is ideal about that behavior? Why would that be a particularly > > good thing to do? > > It is following the rule -- "return back to the caller". That doesn't address the question of why vcpu->arch.secure_guest should be cleared at the point where we do that. Paul.