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From: Cornelia Huck <cohuck@redhat.com>
To: David Hildenbrand <david@redhat.com>
Cc: David Gibson <david@gibson.dropbear.id.au>,
	qemu-devel@nongnu.org, brijesh.singh@amd.com, pair@us.ibm.com,
	pbonzini@redhat.com, dgilbert@redhat.com, frankja@linux.ibm.com,
	Marcel Apfelbaum <marcel.apfelbaum@gmail.com>,
	kvm@vger.kernel.org, qemu-ppc@nongnu.org, mst@redhat.com,
	mdroth@linux.vnet.ibm.com, Richard Henderson <rth@twiddle.net>,
	pasic@linux.ibm.com, Eduardo Habkost <ehabkost@redhat.com>,
	qemu-s390x@nongnu.org
Subject: Re: [PATCH v3 0/9] Generalize memory encryption models
Date: Mon, 22 Jun 2020 14:02:54 +0200	[thread overview]
Message-ID: <20200622140254.0dbe5d8c.cohuck@redhat.com> (raw)
In-Reply-To: <358d48e5-4c57-808b-50da-275f5e2a352c@redhat.com>

On Fri, 19 Jun 2020 12:10:13 +0200
David Hildenbrand <david@redhat.com> wrote:

> On 19.06.20 12:05, Cornelia Huck wrote:
> > On Fri, 19 Jun 2020 11:56:49 +0200
> > David Hildenbrand <david@redhat.com> wrote:
> >   
> >>>>> For now this series covers just AMD SEV and POWER PEF.  I'm hoping it
> >>>>> can be extended to cover the Intel and s390 mechanisms as well,
> >>>>> though.      
> >>>>
> >>>> The only approach on s390x to not glue command line properties to the
> >>>> cpu model would be to remove the CPU model feature and replace it by the
> >>>> command line parameter. But that would, of course, be an incompatible break.    
> >>>
> >>> Yuck.
> >>>
> >>> We still need to provide the cpu feature to the *guest* in any case, no?    
> >>
> >> Yeah, but that could be wired up internally. Wouldn't consider it clean,
> >> though (I second the "overengineered" above).  
> > 
> > Could an internally wired-up cpu feature be introspected? Also, what  
> 
> Nope. It would just be e.g., a "machine feature" indicated to the guest
> via the STFL interface/instruction. I was tackling the introspect part
> when asking David how to sense from upper layers. It would have to be
> sense via a different interface as it would not longer be modeled as
> part of CPU features in QEMU.
> 
> > happens if new cpu features are introduced that have a dependency on or
> > a conflict with this one?  
> 
> Conflict: bail out in QEMU when incompatible options are specified.
> Dependency: warn and continue/fixup (e.g., mask off?)

Masking off would likely be surprising to the user.

> Not clean I think.

I agree.

Still unsure how to bring this new machine property and the cpu feature
together. Would be great to have the same interface everywhere, but
having two distinct command line objects depend on each other sucks.
Automatically setting the feature bit if pv is supported complicates
things further.

(Is there any requirement that the machine object has been already set
up before the cpu features are processed? Or the other way around?)

Does this have any implications when probing with the 'none' machine?


  reply	other threads:[~2020-06-22 12:03 UTC|newest]

Thread overview: 56+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-19  2:05 [PATCH v3 0/9] Generalize memory encryption models David Gibson
2020-06-19  2:05 ` [PATCH v3 1/9] host trust limitation: Introduce new host trust limitation interface David Gibson
2020-06-26 11:01   ` Dr. David Alan Gilbert
2020-07-14 19:26   ` Richard Henderson
2020-06-19  2:05 ` [PATCH v3 2/9] host trust limitation: Handle memory encryption via interface David Gibson
2020-06-19  2:05 ` [PATCH v3 3/9] host trust limitation: Move side effect out of machine_set_memory_encryption() David Gibson
2020-06-19  2:05 ` [PATCH v3 4/9] host trust limitation: Rework the "memory-encryption" property David Gibson
2020-07-14 19:36   ` Richard Henderson
2020-06-19  2:05 ` [PATCH v3 5/9] host trust limitation: Decouple kvm_memcrypt_*() helpers from KVM David Gibson
2020-06-19  2:05 ` [PATCH v3 6/9] host trust limitation: Add Error ** to HostTrustLimitation::kvm_init David Gibson
2020-06-19  2:06 ` [PATCH v3 7/9] spapr: Add PEF based host trust limitation David Gibson
2020-06-19  2:06 ` [PATCH v3 8/9] spapr: PEF: block migration David Gibson
2020-06-26 10:33   ` Dr. David Alan Gilbert
2020-07-05  7:38     ` David Gibson
2020-06-19  2:06 ` [PATCH v3 9/9] host trust limitation: Alter virtio default properties for protected guests David Gibson
2020-06-19 10:12   ` Daniel P. Berrangé
2020-06-19 11:46     ` Michael S. Tsirkin
2020-06-19 11:47       ` Michael S. Tsirkin
2020-06-19 12:16         ` Daniel P. Berrangé
2020-06-19 20:04           ` Halil Pasic
2020-06-24  7:55           ` Michael S. Tsirkin
2020-06-25  4:57             ` David Gibson
2020-06-25  5:02       ` David Gibson
2020-06-19 14:45     ` David Gibson
2020-06-19 15:05       ` Daniel P. Berrangé
2020-06-20  8:24         ` David Gibson
2020-06-22  9:09           ` Daniel P. Berrangé
2020-06-25  5:06             ` David Gibson
2020-06-19  2:42 ` [PATCH v3 0/9] Generalize memory encryption models no-reply
2020-06-19  8:28 ` David Hildenbrand
2020-06-19  9:45   ` Cornelia Huck
2020-06-19  9:56     ` David Hildenbrand
2020-06-19 10:05       ` Cornelia Huck
2020-06-19 10:10         ` David Hildenbrand
2020-06-22 12:02           ` Cornelia Huck [this message]
2020-06-25  5:25             ` David Gibson
2020-06-25  7:06               ` David Hildenbrand
2020-06-26  4:42                 ` David Gibson
2020-06-26  6:53                   ` David Hildenbrand
2020-06-26  9:01                     ` Janosch Frank
2020-06-26  9:32                       ` Daniel P. Berrangé
2020-06-26  9:49                         ` Janosch Frank
2020-06-26 10:29                           ` Dr. David Alan Gilbert
2020-06-26 10:58                             ` Daniel P. Berrangé
2020-06-26 12:49                               ` Janosch Frank
2020-07-01 11:59                                 ` Halil Pasic
2020-06-19  9:48   ` David Gibson
2020-06-19 10:04     ` David Hildenbrand
2020-06-25  5:42       ` David Gibson
2020-06-25  6:59         ` David Hildenbrand
2020-06-25  9:49           ` Cornelia Huck
2020-06-22 14:27 ` Christian Borntraeger
2020-06-24  7:06   ` Cornelia Huck
2020-06-25  5:47     ` David Gibson
2020-06-25  5:48       ` David Gibson
2020-06-25  5:44   ` David Gibson

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