linux-kernel - Re: [PATCH v4 03/15] KVM: s390: refactor crypto initialization

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Message-Id: <2ac8b862-e2dc-843e-a0b8-906fa32b42f4@linux.vnet.ibm.com>
Date:   Tue, 17 Apr 2018 10:26:57 -0400
From:   Tony Krowiak <akrowiak@...ux.vnet.ibm.com>
To:     Cornelia Huck <cohuck@...hat.com>,
        Harald Freudenberger <FREUDE@...ibm.com>
Cc:     Pierre Morel <pmorel@...ux.vnet.ibm.com>,
        alex.williamson@...hat.com, alifm@...ux.vnet.ibm.com,
        berrange@...hat.com, bjsdjshi@...ux.vnet.ibm.com,
        borntrae@...ux.ibm.com, fiuczy@...ux.vnet.ibm.com,
        heicars2@...ux.vnet.ibm.com, jjherne@...ux.vnet.ibm.com,
        kvm@...r.kernel.org, kwankhede@...dia.com,
        linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org,
        mjrosato@...ux.vnet.ibm.com, mschwid2@...ux.vnet.ibm.com,
        pasic@...ux.vnet.ibm.com, pbonzini@...hat.com,
        Reinhard Buendgen <BUENDGEN@...ibm.com>, thuth@...hat.com
Subject: Re: [PATCH v4 03/15] KVM: s390: refactor crypto initialization

On 04/17/2018 06:10 AM, Cornelia Huck wrote:
> On Tue, 17 Apr 2018 09:49:58 +0200
> "Harald Freudenberger" <FREUDE@...ibm.com> wrote:
>
>> Didn't we say that when APXA is not available there is no Crypto support
>> for KVM ?
> [Going by the code, as I don't have access to the architecture]
>
> Current status seems to be:
> - setup crycb if facility 76 is available (that's MSAX3, I guess?)

The crycb is set up regardless of whether STFLE.76 (MSAX3) is
installed or not.

> - use format 2 if APXA is available, else use format 1

Use format 0 if MSAX3 is not available
Use format 1 if MSAX3 is available but APXA is not
Use format 2 if MSAX3 and APXA is available

>
>  From Tony's patch description, the goal seems to be:
> - setup crycb even if MSAX3 is not available

Yes, that is true

>
> So my understanding is that we use APXA only to decide on the format of
> the crycb, but provide it in any case?

Yes, that is true

>
> (Not providing a crycb if APXA is not available would be loss of
> functionality, I guess? Deciding not to provide vfio-ap if APXA is not
> available is a different game, of course.)

This would require a change to enabling the CPU model feature for
AP.

>