From: Paul Mackerras <paulus@ozlabs.org>
To: Ram Pai <linuxram@us.ibm.com>
Cc: Sukadev Bhattiprolu <sukadev@linux.ibm.com>,
cclaudio@linux.ibm.com, kvm-ppc@vger.kernel.org,
Bharata B Rao <bharata@linux.ibm.com>,
linux-mm@kvack.org, jglisse@redhat.com,
Ram Pai <linuxram@linux.ibm.com>,
aneesh.kumar@linux.vnet.ibm.com, paulus@au1.ibm.com,
sukadev@linux.vnet.ibm.com, linuxppc-dev@lists.ozlabs.org,
hch@lst.de
Subject: Re: [PATCH v10 7/8] KVM: PPC: Implement H_SVM_INIT_ABORT hcall
Date: Thu, 14 Nov 2019 08:18:24 +1100 [thread overview]
Message-ID: <20191113211824.GA20535@blackberry> (raw)
In-Reply-To: <20191113063233.GF5159@oc0525413822.ibm.com>
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?
Paul.
next prev parent reply other threads:[~2019-11-13 21:20 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-04 4:17 [PATCH v10 0/8] KVM: PPC: Driver to manage pages of secure guest Bharata B Rao
2019-11-04 4:17 ` [PATCH v10 1/8] mm: ksm: Export ksm_madvise() Bharata B Rao
2019-11-06 4:33 ` Paul Mackerras
2019-11-06 6:45 ` Bharata B Rao
2019-11-07 5:45 ` Paul Mackerras
2019-11-15 14:10 ` Bharata B Rao
2019-11-04 4:17 ` [PATCH v10 2/8] KVM: PPC: Support for running secure guests Bharata B Rao
2019-11-06 4:34 ` Paul Mackerras
2019-11-04 4:17 ` [PATCH v10 3/8] KVM: PPC: Shared pages support for " Bharata B Rao
2019-11-06 4:52 ` Paul Mackerras
2019-11-06 8:22 ` Bharata B Rao
2019-11-06 8:29 ` Bharata B Rao
2019-11-04 4:17 ` [PATCH v10 4/8] KVM: PPC: Radix changes for secure guest Bharata B Rao
2019-11-06 5:58 ` Paul Mackerras
2019-11-06 8:36 ` Bharata B Rao
2019-11-04 4:17 ` [PATCH v10 5/8] KVM: PPC: Handle memory plug/unplug to secure VM Bharata B Rao
2019-11-11 4:25 ` Paul Mackerras
2019-11-04 4:17 ` [PATCH v10 6/8] KVM: PPC: Support reset of secure guest Bharata B Rao
2019-11-11 5:28 ` Paul Mackerras
2019-11-11 6:55 ` Bharata B Rao
2019-11-12 5:34 ` Paul Mackerras
2019-11-13 15:29 ` Bharata B Rao
2019-11-14 5:07 ` Paul Mackerras
2019-11-04 4:17 ` [PATCH v10 7/8] KVM: PPC: Implement H_SVM_INIT_ABORT hcall Bharata B Rao
2019-11-11 4:19 ` Paul Mackerras
2019-11-12 1:01 ` Ram Pai
2019-11-12 5:38 ` Paul Mackerras
2019-11-12 7:52 ` Ram Pai
2019-11-12 11:32 ` Paul Mackerras
2019-11-12 14:45 ` Ram Pai
2019-11-13 0:14 ` Paul Mackerras
2019-11-13 6:32 ` Ram Pai
2019-11-13 21:18 ` Paul Mackerras [this message]
2019-11-13 21:50 ` Ram Pai
2019-11-14 5:08 ` Paul Mackerras
2019-11-14 7:02 ` Ram Pai
2019-11-04 4:18 ` [PATCH v10 8/8] KVM: PPC: Ultravisor: Add PPC_UV config option Bharata B Rao
2019-11-06 4:30 ` [PATCH v10 0/8] KVM: PPC: Driver to manage pages of secure guest Paul Mackerras
2019-11-06 6:20 ` Bharata B Rao
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