From: Christian Borntraeger <borntraeger@de.ibm.com>
To: "Dr. David Alan Gilbert" <dgilbert@redhat.com>,
Cornelia Huck <cohuck@redhat.com>
Cc: Ram Pai <linuxram@us.ibm.com>, Halil Pasic <pasic@linux.ibm.com>,
Greg Kurz <groug@kaod.org>,
pair@us.ibm.com, brijesh.singh@amd.com, kvm@vger.kernel.org,
"Michael S. Tsirkin" <mst@redhat.com>,
qemu-devel@nongnu.org, frankja@linux.ibm.com, david@redhat.com,
mdroth@linux.vnet.ibm.com,
David Gibson <david@gibson.dropbear.id.au>,
thuth@redhat.com, Eduardo Habkost <ehabkost@redhat.com>,
Richard Henderson <richard.henderson@linaro.org>,
qemu-s390x@nongnu.org, rth@twiddle.net, berrange@redhat.com,
Marcelo Tosatti <mtosatti@redhat.com>,
qemu-ppc@nongnu.org, pbonzini@redhat.com
Subject: Re: [for-6.0 v5 11/13] spapr: PEF: prevent migration
Date: Thu, 14 Jan 2021 11:28:46 +0100 [thread overview]
Message-ID: <6e02e8d5-af4b-624b-1a12-d03b9d554a41@de.ibm.com> (raw)
In-Reply-To: <20210113124226.GH2938@work-vm>
On 13.01.21 13:42, Dr. David Alan Gilbert wrote:
> * Cornelia Huck (cohuck@redhat.com) wrote:
>> On Tue, 5 Jan 2021 12:41:25 -0800
>> Ram Pai <linuxram@us.ibm.com> wrote:
>>
>>> On Tue, Jan 05, 2021 at 11:56:14AM +0100, Halil Pasic wrote:
>>>> On Mon, 4 Jan 2021 10:40:26 -0800
>>>> Ram Pai <linuxram@us.ibm.com> wrote:
>>
>>>>> The main difference between my proposal and the other proposal is...
>>>>>
>>>>> In my proposal the guest makes the compatibility decision and acts
>>>>> accordingly. In the other proposal QEMU makes the compatibility
>>>>> decision and acts accordingly. I argue that QEMU cannot make a good
>>>>> compatibility decision, because it wont know in advance, if the guest
>>>>> will or will-not switch-to-secure.
>>>>>
>>>>
>>>> You have a point there when you say that QEMU does not know in advance,
>>>> if the guest will or will-not switch-to-secure. I made that argument
>>>> regarding VIRTIO_F_ACCESS_PLATFORM (iommu_platform) myself. My idea
>>>> was to flip that property on demand when the conversion occurs. David
>>>> explained to me that this is not possible for ppc, and that having the
>>>> "securable-guest-memory" property (or whatever the name will be)
>>>> specified is a strong indication, that the VM is intended to be used as
>>>> a secure VM (thus it is OK to hurt the case where the guest does not
>>>> try to transition). That argument applies here as well.
>>>
>>> As suggested by Cornelia Huck, what if QEMU disabled the
>>> "securable-guest-memory" property if 'must-support-migrate' is enabled?
>>> Offcourse; this has to be done with a big fat warning stating
>>> "secure-guest-memory" feature is disabled on the machine.
>>> Doing so, will continue to support guest that do not try to transition.
>>> Guest that try to transition will fail and terminate themselves.
>>
>> Just to recap the s390x situation:
>>
>> - We currently offer a cpu feature that indicates secure execution to
>> be available to the guest if the host supports it.
>> - When we introduce the secure object, we still need to support
>> previous configurations and continue to offer the cpu feature, even
>> if the secure object is not specified.
>> - As migration is currently not supported for secured guests, we add a
>> blocker once the guest actually transitions. That means that
>> transition fails if --only-migratable was specified on the command
>> line. (Guests not transitioning will obviously not notice anything.)
>> - With the secure object, we will already fail starting QEMU if
>> --only-migratable was specified.
>>
>> My suggestion is now that we don't even offer the cpu feature if
>> --only-migratable has been specified. For a guest that does not want to
>> transition to secure mode, nothing changes; a guest that wants to
>> transition to secure mode will notice that the feature is not available
>> and fail appropriately (or ultimately, when the ultravisor call fails).
>> We'd still fail starting QEMU for the secure object + --only-migratable
>> combination.
>>
>> Does that make sense?
>
> It's a little unusual; I don't think we have any other cases where
> --only-migratable changes the behaviour; I think it normally only stops
> you doing something that would have made it unmigratable or causes
> an operation that would make it unmigratable to fail.
I would like to NOT block this feature with --only-migrateable. A guest
can startup unprotected (and then is is migrateable). the migration blocker
is really a dynamic aspect during runtime.
next prev parent reply other threads:[~2021-01-14 10:30 UTC|newest]
Thread overview: 93+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-04 5:44 [for-6.0 v5 00/13] Generalize memory encryption models David Gibson
2020-12-04 5:44 ` [for-6.0 v5 01/13] qom: Allow optional sugar props David Gibson
2020-12-04 12:57 ` Cornelia Huck
2020-12-14 21:25 ` Eduardo Habkost
2021-01-11 18:04 ` Philippe Mathieu-Daudé
2020-12-04 5:44 ` [for-6.0 v5 02/13] securable guest memory: Introduce new securable guest memory base class David Gibson
2020-12-04 5:44 ` [for-6.0 v5 03/13] securable guest memory: Handle memory encryption via interface David Gibson
2020-12-04 13:10 ` Cornelia Huck
2021-01-08 4:03 ` David Gibson
2021-01-12 3:49 ` David Gibson
2020-12-04 5:44 ` [for-6.0 v5 04/13] securable guest memory: Move side effect out of machine_set_memory_encryption() David Gibson
2020-12-04 5:44 ` [for-6.0 v5 05/13] securable guest memory: Rework the "memory-encryption" property David Gibson
2021-01-11 18:09 ` Philippe Mathieu-Daudé
2020-12-04 5:44 ` [for-6.0 v5 06/13] securable guest memory: Decouple kvm_memcrypt_*() helpers from KVM David Gibson
2021-01-11 18:13 ` Philippe Mathieu-Daudé
2021-01-12 3:03 ` David Gibson
2020-12-04 5:44 ` [for-6.0 v5 07/13] sev: Add Error ** to sev_kvm_init() David Gibson
2020-12-14 16:50 ` Cornelia Huck
2020-12-04 5:44 ` [for-6.0 v5 08/13] securable guest memory: Introduce sgm "ready" flag David Gibson
2020-12-14 17:00 ` Cornelia Huck
2020-12-17 5:38 ` David Gibson
2020-12-17 11:24 ` Cornelia Huck
2020-12-04 5:44 ` [for-6.0 v5 09/13] securable guest memory: Move SEV initialization into arch specific code David Gibson
2020-12-04 5:44 ` [for-6.0 v5 10/13] spapr: Add PEF based securable guest memory David Gibson
2021-01-05 23:34 ` Ram Pai
2021-01-08 0:34 ` David Gibson
2020-12-04 5:44 ` [for-6.0 v5 11/13] spapr: PEF: prevent migration David Gibson
2020-12-14 17:22 ` Cornelia Huck
2020-12-17 5:47 ` David Gibson
2020-12-17 11:38 ` Cornelia Huck
2020-12-17 14:15 ` Greg Kurz
2020-12-18 11:41 ` Cornelia Huck
2020-12-18 12:08 ` Dr. David Alan Gilbert
2021-01-04 7:15 ` Ram Pai
2021-01-04 12:46 ` [EXTERNAL] " Halil Pasic
2021-01-04 18:40 ` Ram Pai
2021-01-05 10:56 ` [EXTERNAL] " Halil Pasic
2021-01-05 20:41 ` Ram Pai
2021-01-11 16:59 ` Cornelia Huck
2021-01-11 19:58 ` Ram Pai
2021-01-12 8:19 ` Cornelia Huck
2021-01-12 18:55 ` Ram Pai
2021-01-13 8:06 ` Cornelia Huck
2021-01-15 18:55 ` Ram Pai
2021-01-19 8:19 ` Cornelia Huck
2021-01-19 9:59 ` Daniel P. Berrangé
2021-01-14 11:23 ` Daniel P. Berrangé
2021-01-13 12:42 ` Dr. David Alan Gilbert
2021-01-14 10:28 ` Christian Borntraeger [this message]
2021-01-14 10:36 ` Dr. David Alan Gilbert
2021-01-14 10:52 ` Christian Borntraeger
2021-01-14 11:05 ` Cornelia Huck
2021-01-14 11:45 ` Dr. David Alan Gilbert
2021-01-14 11:50 ` Christian Borntraeger
2021-01-14 12:20 ` Daniel P. Berrangé
2021-01-14 14:04 ` Cornelia Huck
2021-01-14 14:09 ` Christian Borntraeger
2021-01-14 14:15 ` Daniel P. Berrangé
2021-01-14 15:25 ` Christian Borntraeger
2021-01-14 15:33 ` Daniel P. Berrangé
2021-01-15 18:24 ` Ram Pai
2021-01-14 11:25 ` Daniel P. Berrangé
2021-01-14 23:51 ` David Gibson
2021-01-18 17:39 ` Dr. David Alan Gilbert
2021-01-19 8:28 ` Christian Borntraeger
2021-01-19 8:34 ` Cornelia Huck
2020-12-04 5:44 ` [for-6.0 v5 12/13] securable guest memory: Alter virtio default properties for protected guests David Gibson
2020-12-04 8:10 ` Christian Borntraeger
2020-12-04 8:17 ` Cornelia Huck
2020-12-04 8:29 ` Christian Borntraeger
2020-12-04 14:43 ` Halil Pasic
2020-12-08 1:54 ` David Gibson
2020-12-08 8:16 ` Christian Borntraeger
2020-12-08 10:28 ` Halil Pasic
2020-12-08 12:50 ` Cornelia Huck
2020-12-17 5:53 ` David Gibson
2020-12-04 17:04 ` Cornelia Huck
2020-12-04 5:44 ` [for-6.0 v5 13/13] s390: Recognize securable-guest-memory option David Gibson
2020-12-15 11:45 ` Cornelia Huck
2020-12-17 5:54 ` David Gibson
2020-12-04 8:06 ` [for-6.0 v5 00/13] Generalize memory encryption models Christian Borntraeger
2020-12-04 13:02 ` Cornelia Huck
2020-12-04 13:07 ` Dr. David Alan Gilbert
2020-12-04 13:12 ` Cornelia Huck
2020-12-08 2:57 ` David Gibson
2020-12-08 12:43 ` Cornelia Huck
2020-12-17 6:21 ` David Gibson
2020-12-17 11:43 ` Cornelia Huck
2020-12-04 13:25 ` Daniel P. Berrangé
2020-12-04 13:51 ` Halil Pasic
2020-12-08 2:54 ` David Gibson
2020-12-04 9:50 ` Daniel P. Berrangé
2021-01-12 3:02 ` David Gibson
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