linux-kernel - Re: [PATCH v3 01/14] KVM: s390: refactor crypto initialization

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Message-Id: <5c659a5e-1933-366b-65fc-6e9eabe504d5@linux.vnet.ibm.com>
Date:   Thu, 29 Mar 2018 14:57:22 -0400
From:   Tony Krowiak <akrowiak@...ux.vnet.ibm.com>
To:     Cornelia Huck <cohuck@...hat.com>,
        Pierre Morel <pmorel@...ux.vnet.ibm.com>
Cc:     linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, freude@...ibm.com, schwidefsky@...ibm.com,
        heiko.carstens@...ibm.com, borntraeger@...ibm.com,
        kwankhede@...dia.com, bjsdjshi@...ux.vnet.ibm.com,
        pbonzini@...hat.com, alex.williamson@...hat.com,
        alifm@...ux.vnet.ibm.com, mjrosato@...ux.vnet.ibm.com,
        jjherne@...ux.vnet.ibm.com, thuth@...hat.com,
        pasic@...ux.vnet.ibm.com, berrange@...hat.com,
        fiuczy@...ux.vnet.ibm.com, buendgen@...ibm.com
Subject: Re: [PATCH v3 01/14] KVM: s390: refactor crypto initialization

On 03/26/2018 04:44 AM, Cornelia Huck wrote:
> On Thu, 15 Mar 2018 15:55:39 +0100
> Pierre Morel <pmorel@...ux.vnet.ibm.com> wrote:
>
>> On 15/03/2018 15:48, Tony Krowiak wrote:
>>> On 03/15/2018 08:26 AM, Pierre Morel wrote:
>>>> On 14/03/2018 19:25, Tony Krowiak wrote:
>>>>> diff --git a/arch/s390/kvm/Kconfig b/arch/s390/kvm/Kconfig
>>>>> index a3dbd45..4ca9077 100644
>>>>> --- a/arch/s390/kvm/Kconfig
>>>>> +++ b/arch/s390/kvm/Kconfig
>>>>> @@ -33,6 +33,7 @@ config KVM
>>>>>        select HAVE_KVM_INVALID_WAKEUPS
>>>>>        select SRCU
>>>>>        select KVM_VFIO
>>>>> +    select ZCRYPT
>>>> I do not think it is a good solution to *always* enable ZCRYPT
>>>> when we have KVM.
>>> If CONFIG_ZCRYPT is not selected, then the kvm_ap_apxa_installed()
>>> function will not compile
>>> because it calls a zcrypt interface. How would you suggest we make
>>> sure zcrypt interfaces
>>> used in KVM are built if CONFIG_ZCRYPT is not selected?
>> if zcrypt is not configured, I suppose that the KVM code initializaing CRYCB
>> has no use but the function will be called from KVM.
>> So I would do something like:
>>
>> #ifdef ZCRYPT
>> external definitions.
>> #else
>> stubs returning error -ENOZCRYPT (or whatever)
>> #endif
> The kvm code used some kind of detection for crycb before (IIRC it was
> for the key-wrapping stuff). I assume that usage is independent of
> zcrypt driver usage in the host?
A function in kvm-s390.c was replaced with a call to the function in
ap_bus.c that was externalized in patch 2/14. This was done to remove
duplicate code. Since zcrypt is built into the kernel, I didn't think
it would be a problem, but apparently because of the way zcrypt is
configured, it is still possible to remove it from the kernel build.
>
> So, I think that apxa detection function should be used to s390
> architecture base code and not be conditional on anything.
I am convinced that the original function from kvm_s390.c should be
restored.
>