Messages in this thread | | | Subject | Re: [PATCH v4 01/15] s390: zcrypt: externalize AP instructions available function | From | Tony Krowiak <> | Date | Tue, 17 Apr 2018 14:14:49 -0400 |
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On 04/17/2018 12:56 PM, Cornelia Huck wrote: > On Tue, 17 Apr 2018 09:31:00 -0400 > Tony Krowiak <akrowiak@linux.vnet.ibm.com> wrote: > >> My preference would be one of the following: >> >> 1. All of the interfaces defined in arch/s390/include/asm/ap.h >> are implemented in a file that is built whether ZCRYPT is >> built or not. >> >> 2. The drivers/s390/crypto/ap_asm.h file containing the functions >> that execute the AP instructions are made available outside of >> the AP bus, for example; arch/s390/include/asm >> >> I requested this from the maintainer but was told we don't want to >> have any crypto adapter support when the host AP functionality is >> disabled (CONFIG_ZCRYPT=n). This makes sense, however; I think it is >> a bit confusing to have a header file (arch/s390/include/asm/ap.h) >> with interfaces that are conditionally built. >> >> This is why I chose the ifdeffery (as you call it) approach. The >> only other solution I can conjure is to duplicate the asm code for >> the AP instructions needed in KVM and bypass using the AP bus >> interfaces. > I think at the root of this is an unfortunate mixup in the > architecture: The format of the crycb changes depending on some ap > feature being installed. Providing the crycb does not have anything to > do with ap device usage in the host, but we need to issue an ap > instruction to get this right. [Correct me if I'm wrong; but that's > what I get without being able to consult the actual architecture.]
That sums it up.
> > So, exporting *all* of the interfaces is probably not needed anyway. I > think it boils down to either "export the interfaces where a mixup > happened, and keep the rest to zcrypt only", or "duplicate the > instructions for kvm usage".
I only suggested exporting all of the interfaces because the others may be needed down the road when interception is implemented for full virtualization of AP devices.
> > I hope we can find a solution here, as this seems to be one of the main > discussion points :/ (FWIW, I think the basic driver interface is sane.)
I will work on coming up with something that attempts to take into consideration all of the comments thus far. In the meantime, I will keep my eyes on this space if anybody comes up with a better, concrete resolution.
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