lkml.org 
[lkml]   [2018]   [Apr]   [17]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    SubjectRe: [PATCH v4 01/15] s390: zcrypt: externalize AP instructions available function
    From
    Date
    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.

    >

    \
     
     \ /
      Last update: 2018-04-17 20:15    [W:3.610 / U:0.740 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site