linux-kernel - Re: [PATCH] KVM: X86: Add missing KVM

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Message-ID: <713d35b9-5dd5-284f-b514-7d2295a2db34@redhat.com>
Date:   Sat, 6 Oct 2018 00:18:30 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     Radim Krčmář <rkrcmar@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org, kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Brijesh Singh <brijesh.singh@....com>,
        Borislav Petkov <bp@...e.de>
Subject: Re: [PATCH] KVM: X86: Add missing KVM_AMD dependency

On 06/10/2018 00:03, Guenter Roeck wrote:
>> This should be handled by
>>
>> config KVM_AMD_SEV
>>         def_bool y
>>         bool "AMD Secure Encrypted Virtualization (SEV) support"
>>         depends on KVM_AMD && X86_64
>>         depends on CRYPTO_DEV_SP_PSP && !(KVM_AMD=y && CRYPTO_DEV_CCP_DD=m)
>>         ---help---
>>         Provides support for launching Encrypted VMs on AMD processors.
>>
> Unfortunately it doesn't. It disables KVM_AMD_SEV, but that doesn't prevent
> the calls.

Yes, exactly - that's why I mentioned the sev_guest patch that should
cull all the SEV code from a !KVM_AMD_SEV build.

>> Maybe this works as well?  I haven't tested it yet:
>>
> I am sure there are many possible solutions. I would personally prefer one
> that enforces KVM_AMD=m with CRYPTO_DEV_CCP_DD=m, but that is just me.

Well, KVM_AMD=y is a relatively unusual choice to begin with.  The
question is whether then you want to disable this choice completely when
CRYPTO_DEV_CCP_DD=m, or just disable SEV.

My patch is a good idea anyway, if I may say so :), because it culls a
lot of code from a !KVM_AMD_SEV build.  But if it is not enough, we
certainly have to do something else about the failure you're reporting.

Paolo