Messages in this thread | | | Date | Tue, 17 Apr 2018 17:21:39 +0200 | From | Cornelia Huck <> | Subject | Re: [PATCH v4 03/15] KVM: s390: refactor crypto initialization |
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On Tue, 17 Apr 2018 10:26:57 -0400 Tony Krowiak <akrowiak@linux.vnet.ibm.com> wrote:
> On 04/17/2018 06:10 AM, Cornelia Huck wrote: > > On Tue, 17 Apr 2018 09:49:58 +0200 > > "Harald Freudenberger" <FREUDE@de.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.
Hm, the current code does a quick exit if bit 76 is not set, doesn't it?
> > > - 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
With the format selection you outlined above, I guess. Makes sense from my point of view (just looking at the source code).
> > > > > (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.
But would it actually make sense to tie vfio-ap to APXA? This needs to be answered by folks with access to the architecture :)
[Personally, I think we should go with the version that uses the least restrictions without introducing over-complex code. What constitutes "over-complex code" is of course in the eye of the beholder...]
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