Re: [PATCH v7 13/13] s390: Recognize confidential-guest-support option
On 15.01.21 17:36, Cornelia Huck wrote:
> On Thu, 14 Jan 2021 10:58:11 +1100
> David Gibson wrote:
>
>> At least some s390 cpu models support "Protected Virtualization" (PV),
>> a mechanism to protect guests from eavesdropping by a compromised
>> hypervisor.
>>
>> This is similar in function to other mechanisms like AMD's SEV and
>> POWER's PEF, which are controlled by the "confidential-guest-support"
>> machine option. s390 is a slightly special case, because we already
>> supported PV, simply by using a CPU model with the required feature
>> (S390_FEAT_UNPACK).
>>
>> To integrate this with the option used by other platforms, we
>> implement the following compromise:
>>
>> - When the confidential-guest-support option is set, s390 will
>>recognize it, verify that the CPU can support PV (failing if not)
>>and set virtio default options necessary for encrypted or protected
>>guests, as on other platforms. i.e. if confidential-guest-support
>>is set, we will either create a guest capable of entering PV mode,
>>or fail outright.
>>
>> - If confidential-guest-support is not set, guests might still be
>>able to enter PV mode, if the CPU has the right model. This may be
>>a little surprising, but shouldn't actually be harmful.
>>
>> To start a guest supporting Protected Virtualization using the new
>> option use the command line arguments:
>> -object s390-pv-guest,id=pv0 -machine confidential-guest-support=pv0
>>
>> Signed-off-by: David Gibson
>> ---
>> docs/confidential-guest-support.txt | 3 ++
>> docs/system/s390x/protvirt.rst | 19 ++---
>> hw/s390x/pv.c | 62 +
>> include/hw/s390x/pv.h | 1 +
>> target/s390x/kvm.c | 3 ++
>> 5 files changed, 82 insertions(+), 6 deletions(-)
>>
>
> (...)
>
>> +int s390_pv_init(ConfidentialGuestSupport *cgs, Error **errp)
>> +{
>> +if (!object_dynamic_cast(OBJECT(cgs), TYPE_S390_PV_GUEST)) {
>> +return 0;
>> +}
>> +
>> +if (!s390_has_feat(S390_FEAT_UNPACK)) {
>> +error_setg(errp,
>> + "CPU model does not support Protected Virtualization");
>> +return -1;
>> +}
>> +
>> +cgs->ready = true;
>> +
>> +return 0;
>> +}
>
> Do we want to add a migration blocker here? If we keep the one that is
> added when the guest transitions, we'll end up with two of them, but
> that might be easier than trying to unify it.
that whould be fine with me. We still need to move things around to
make sure that the cpu model is already in place, though.
Re: [PATCH v7 13/13] s390: Recognize confidential-guest-support option
On Thu, 14 Jan 2021 10:58:11 +1100
David Gibson wrote:
> At least some s390 cpu models support "Protected Virtualization" (PV),
> a mechanism to protect guests from eavesdropping by a compromised
> hypervisor.
>
> This is similar in function to other mechanisms like AMD's SEV and
> POWER's PEF, which are controlled by the "confidential-guest-support"
> machine option. s390 is a slightly special case, because we already
> supported PV, simply by using a CPU model with the required feature
> (S390_FEAT_UNPACK).
>
> To integrate this with the option used by other platforms, we
> implement the following compromise:
>
> - When the confidential-guest-support option is set, s390 will
>recognize it, verify that the CPU can support PV (failing if not)
>and set virtio default options necessary for encrypted or protected
>guests, as on other platforms. i.e. if confidential-guest-support
>is set, we will either create a guest capable of entering PV mode,
>or fail outright.
>
> - If confidential-guest-support is not set, guests might still be
>able to enter PV mode, if the CPU has the right model. This may be
>a little surprising, but shouldn't actually be harmful.
>
> To start a guest supporting Protected Virtualization using the new
> option use the command line arguments:
> -object s390-pv-guest,id=pv0 -machine confidential-guest-support=pv0
>
> Signed-off-by: David Gibson
> ---
> docs/confidential-guest-support.txt | 3 ++
> docs/system/s390x/protvirt.rst | 19 ++---
> hw/s390x/pv.c | 62 +
> include/hw/s390x/pv.h | 1 +
> target/s390x/kvm.c | 3 ++
> 5 files changed, 82 insertions(+), 6 deletions(-)
>
(...)
> +int s390_pv_init(ConfidentialGuestSupport *cgs, Error **errp)
> +{
> +if (!object_dynamic_cast(OBJECT(cgs), TYPE_S390_PV_GUEST)) {
> +return 0;
> +}
> +
> +if (!s390_has_feat(S390_FEAT_UNPACK)) {
> +error_setg(errp,
> + "CPU model does not support Protected Virtualization");
> +return -1;
> +}
> +
> +cgs->ready = true;
> +
> +return 0;
> +}
Do we want to add a migration blocker here? If we keep the one that is
added when the guest transitions, we'll end up with two of them, but
that might be easier than trying to unify it.
Re: [PATCH v7 13/13] s390: Recognize confidential-guest-support option
On Thu, Jan 14, 2021 at 10:24:57AM +0100, Christian Borntraeger wrote:
>
>
> On 14.01.21 10:19, Christian Borntraeger wrote:
> >
> >
> > On 14.01.21 10:10, Christian Borntraeger wrote:
> >>
> >>
> >> On 14.01.21 00:58, David Gibson wrote:
> >> [...]
> >>> +int s390_pv_init(ConfidentialGuestSupport *cgs, Error **errp)
> >>> +{
> >>> +if (!object_dynamic_cast(OBJECT(cgs), TYPE_S390_PV_GUEST)) {
> >>> +return 0;
> >>> +}
> >>> +
> >>> +if (!s390_has_feat(S390_FEAT_UNPACK)) {
> >>> +error_setg(errp,
> >>> + "CPU model does not support Protected
> >>> Virtualization");
> >>> +return -1;
> >>> +}
> >>
> >> I am triggering this and I guess this is because the cpu model is not yet
> >> initialized at
> >> this point in time.
> >>
> > When I remove the check, things seems to work though ( I can access
> > virtio-blk devices without
> > specifying iommu for example)
>
> Maybe we can turn things around and check in apply_cpu_model if the object
> exists but
> unpack was not specified?
That might work. If unpack *is* specified, you'd also need to set the
ready flag there, of course.
--
David Gibson| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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Re: [PATCH v7 13/13] s390: Recognize confidential-guest-support option
On Thu, Jan 14, 2021 at 10:10:02AM +0100, Christian Borntraeger wrote:
>
>
> On 14.01.21 00:58, David Gibson wrote:
> [...]
> > +int s390_pv_init(ConfidentialGuestSupport *cgs, Error **errp)
> > +{
> > +if (!object_dynamic_cast(OBJECT(cgs), TYPE_S390_PV_GUEST)) {
> > +return 0;
> > +}
> > +
> > +if (!s390_has_feat(S390_FEAT_UNPACK)) {
> > +error_setg(errp,
> > + "CPU model does not support Protected Virtualization");
> > +return -1;
> > +}
>
> I am triggering this and I guess this is because the cpu model is not yet
> initialized at
> this point in time.
Bother. I thought I'd put the s390_pv_init() call late enough to
avoid that, but I guess not. Any chance you can debug that? Working
on s390 is far from easy for me.
--
David Gibson| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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Re: [PATCH v7 13/13] s390: Recognize confidential-guest-support option
On 14.01.21 10:19, Christian Borntraeger wrote:
>
>
> On 14.01.21 10:10, Christian Borntraeger wrote:
>>
>>
>> On 14.01.21 00:58, David Gibson wrote:
>> [...]
>>> +int s390_pv_init(ConfidentialGuestSupport *cgs, Error **errp)
>>> +{
>>> +if (!object_dynamic_cast(OBJECT(cgs), TYPE_S390_PV_GUEST)) {
>>> +return 0;
>>> +}
>>> +
>>> +if (!s390_has_feat(S390_FEAT_UNPACK)) {
>>> +error_setg(errp,
>>> + "CPU model does not support Protected Virtualization");
>>> +return -1;
>>> +}
>>
>> I am triggering this and I guess this is because the cpu model is not yet
>> initialized at
>> this point in time.
>>
> When I remove the check, things seems to work though ( I can access
> virtio-blk devices without
> specifying iommu for example)
Maybe we can turn things around and check in apply_cpu_model if the object
exists but
unpack was not specified?
Re: [PATCH v7 13/13] s390: Recognize confidential-guest-support option
On 14.01.21 10:10, Christian Borntraeger wrote:
>
>
> On 14.01.21 00:58, David Gibson wrote:
> [...]
>> +int s390_pv_init(ConfidentialGuestSupport *cgs, Error **errp)
>> +{
>> +if (!object_dynamic_cast(OBJECT(cgs), TYPE_S390_PV_GUEST)) {
>> +return 0;
>> +}
>> +
>> +if (!s390_has_feat(S390_FEAT_UNPACK)) {
>> +error_setg(errp,
>> + "CPU model does not support Protected Virtualization");
>> +return -1;
>> +}
>
> I am triggering this and I guess this is because the cpu model is not yet
> initialized at
> this point in time.
>
When I remove the check, things seems to work though ( I can access virtio-blk
devices without
specifying iommu for example)
Re: [PATCH v7 13/13] s390: Recognize confidential-guest-support option
On 14.01.21 00:58, David Gibson wrote:
[...]
> +int s390_pv_init(ConfidentialGuestSupport *cgs, Error **errp)
> +{
> +if (!object_dynamic_cast(OBJECT(cgs), TYPE_S390_PV_GUEST)) {
> +return 0;
> +}
> +
> +if (!s390_has_feat(S390_FEAT_UNPACK)) {
> +error_setg(errp,
> + "CPU model does not support Protected Virtualization");
> +return -1;
> +}
I am triggering this and I guess this is because the cpu model is not yet
initialized at
this point in time.
