From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ram Pai Date: Wed, 13 Nov 2019 06:32:33 +0000 Subject: Re: [PATCH v10 7/8] KVM: PPC: Implement H_SVM_INIT_ABORT hcall Message-Id: <20191113063233.GF5159@oc0525413822.ibm.com> List-Id: References: <20191104041800.24527-1-bharata@linux.ibm.com> <20191104041800.24527-8-bharata@linux.ibm.com> <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> In-Reply-To: <20191113001427.GA17829@oak.ozlabs.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Paul Mackerras 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 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. RP