linux-kernel - Re: [PATCH v1] KVM: s390: vsie: fix Do the CRYCB validation first

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Message-ID: <ccdc89cd-5299-e674-3329-74e9131dd874@redhat.com>
Date:   Fri, 1 Feb 2019 11:56:55 +0100
From:   David Hildenbrand <david@...hat.com>
To:     Pierre Morel <pmorel@...ux.ibm.com>, borntraeger@...ibm.com
Cc:     linux-kernel@...r.kernel.org, cohuck@...hat.com,
        linux-s390@...r.kernel.org, kvm@...r.kernel.org,
        frankja@...ux.ibm.com, akrowiak@...ux.ibm.com, pasic@...ux.ibm.com
Subject: Re: [PATCH v1] KVM: s390: vsie: fix Do the CRYCB validation first

On 01.02.19 10:52, Pierre Morel wrote:
> The case when the SIE for guest3 is not setup for using
> encryption keys nor Adjunct processor but the guest2
> does use these features was not properly handled.
> 
> This leads SIE entry for guest3 to crash with validity intercept
> because the guest2, not having the use of encryption keys nor
> Adjunct Processor did not initialize the CRYCB designation.
> 
> In the case where none of ECA_APIE, ECB3_AES or ECB3_DEA
> are set in guest3 a format 0 CRYCB is allowed for guest3
> and the CRYCB designation in the SIE for guest3 is not checked
> on SIE entry.
> 
> Let's allow the CRYCD designation to be ignored when the
> SIE for guest3 is not initialized for encryption key usage
> nor AP.
> 
> Fixup: d6f6959 (KVM: s390: vsie: Do the CRYCB validation first)
> 
> Signed-off-by: Pierre Morel <pmorel@...ux.ibm.com>
> Reported-by: Claudio Imbrenda <imbrenda@...ux.ibm.com>
> ---
>  arch/s390/kvm/vsie.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/arch/s390/kvm/vsie.c b/arch/s390/kvm/vsie.c
> index a153257..a748f76 100644
> --- a/arch/s390/kvm/vsie.c
> +++ b/arch/s390/kvm/vsie.c
> @@ -300,6 +300,9 @@ static int shadow_crycb(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
>  	if (!apie_h && !key_msk)
>  		return 0;
>  
> +	if (!(scb_o->eca & ECA_APIE) && !(scb_o->ecb3 & (ECB3_AES | ECB3_DEA)))
> +		return 0;
> +
>  	if (!crycb_addr)
>  		return set_validity_icpt(scb_s, 0x0039U);
>  
> 

The original patch said

"We need to handle the validity checks for the crycb, no matter what the
 settings for the keywrappings are. So lets move the keywrapping checks
 after we have done the validy checks."

Can you explain why keywrapping now is important? These patches seem to
contradict.

-- 

Thanks,

David / dhildenb