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Subject: Re: [PATCH v2 01/15] KVM: s390: refactor crypto initialization
To:     Cornelia Huck <cohuck@redhat.com>
Cc:     linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org,
        kvm@vger.kernel.org, freude@de.ibm.com, schwidefsky@de.ibm.com,
        heiko.carstens@de.ibm.com, borntraeger@de.ibm.com,
        kwankhede@nvidia.com, bjsdjshi@linux.vnet.ibm.com,
        pbonzini@redhat.com, alex.williamson@redhat.com,
        pmorel@linux.vnet.ibm.com, alifm@linux.vnet.ibm.com,
        mjrosato@linux.vnet.ibm.com, jjherne@linux.vnet.ibm.com,
        thuth@redhat.com, pasic@linux.vnet.ibm.com,
        fiuczy@linux.vnet.ibm.com, buendgen@de.ibm.com
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 <20180301105915.5c871524.cohuck@redhat.com>
From:   Tony Krowiak <akrowiak@linux.vnet.ibm.com>
Date:   Wed, 14 Mar 2018 12:02:05 -0400
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On 03/01/2018 04:59 AM, Cornelia Huck wrote:
> On Wed, 28 Feb 2018 16:23:29 -0500
> Tony Krowiak <akrowiak@linux.vnet.ibm.com> wrote:
>
>> On 02/28/2018 12:37 PM, Cornelia Huck wrote:
>>> On Tue, 27 Feb 2018 09:27:59 -0500
>>> Tony Krowiak <akrowiak@linux.vnet.ibm.com> wrote:
>>>> diff --git a/arch/s390/kvm/kvm-ap.c b/arch/s390/kvm/kvm-ap.c
>>>> new file mode 100644
>>>> index 0000000..5305f4c
>>>> --- /dev/null
>>>> +++ b/arch/s390/kvm/kvm-ap.c
>>>> @@ -0,0 +1,47 @@
>>>> +/*
>>>> + * Adjunct Processor (AP) configuration management for KVM guests
>>>> + *
>>>> + * Copyright IBM Corp. 2017
>>>> + *
>>>> + * Author(s): Tony Krowiak <akrowia@linux.vnet.ibm.com>
>>>> + */
>>>> +
>>>> +#include <asm/kvm-ap.h>
>>>> +#include <asm/ap.h>
>>>> +
>>>> +#include "kvm-s390.h"
>>>> +
>>>> +static int kvm_ap_apxa_installed(void)
>>>> +{
>>>> +	int ret;
>>>> +	struct ap_config_info config;
>>>> +
>>>> +	ret = ap_query_configuration(&config);
>>> Doesn't that introduce a dependency on CONFIG_ZCRYPT?
>> It does, but AFAIK zcrypt is built into the kernel. Or is that not what
>> you are asking?
> It is built into the kernel (and not into a module) if CONFIG_ZCRYPT is
> set. When I compile a kernel with CONFIG_KVM set and CONFIG_ZCRYPT
> unset, with this patch applied I get
>
> arch/s390/kvm/kvm-ap.o: In function `kvm_ap_apxa_installed':
> /home/cohuck/git/linux/arch/s390/kvm/kvm-ap.c:19: undefined reference to `ap_query_configuration'
>
> So I'm afraid you cannot use ap_query_configuration() in base s390 kvm
> code unless you move that function to a place where it is always built
> (or at least always built if either CONFIG_KVM or CONFIG_ZCRYPT are
> set).
I was able to get around this by inserting the following into 
arch/s390/kvm/Kconfig:

config KVM
     def_tristate y
     prompt "Kernel-based Virtual Machine (KVM) support"
     depends on HAVE_KVM
     select PREEMPT_NOTIFIERS
...
     select ZCRYPT

If this is a problem, we can discuss it in the v3 which is forthcoming 
very shortly
>