linux-kernel - Re: [PATCH v2 3/5] KVM: s390: vsie: Allow support for a host without AP

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Date:   Wed, 22 Aug 2018 19:06:09 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Pierre Morel <pmorel@...ux.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,
        borntraeger@...ibm.com, schwidefsky@...ibm.com,
        heiko.carstens@...ibm.com
Subject: Re: [PATCH v2 3/5] KVM: s390: vsie: Allow support for a host without
 AP

On 22.08.2018 18:51, Pierre Morel wrote:
> Currently the CRYCB format used in the host for the
> shadowed CRYCB is FORMAT2 while no check is done if
> AP instructions are supported in the host.
> 
> We better use the format the host calculated for the
> guest 1 as the host already tested it against its
> facility set.
> 
> Signed-off-by: Pierre Morel <pmorel@...ux.ibm.com>
> ---
>  arch/s390/kvm/vsie.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/s390/kvm/vsie.c b/arch/s390/kvm/vsie.c
> index 56a9d47..0b12916 100644
> --- a/arch/s390/kvm/vsie.c
> +++ b/arch/s390/kvm/vsie.c
> @@ -154,6 +154,7 @@ static int shadow_crycb(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
>  	const u32 crycb_addr = crycbd_o & 0x7ffffff8U;
>  	unsigned long *b1, *b2;
>  	u8 ecb3_flags;
> +	unsigned long g1_fmt;
>  
>  	scb_s->crycbd = 0;
>  	if (!(crycbd_o == CRYCB_FORMAT1))
> @@ -180,8 +181,8 @@ static int shadow_crycb(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
>  		return set_validity_icpt(scb_s, 0x0035U);
>  
>  	scb_s->ecb3 |= ecb3_flags;
> -	scb_s->crycbd = ((__u32)(__u64) &vsie_page->crycb) | CRYCB_FORMAT1 |
> -			CRYCB_FORMAT2;
> +	g1_fmt = vcpu->arch.sie_block->crycbd & 0x03;
> +	scb_s->crycbd = ((__u32)(__u64) &vsie_page->crycb) | g1_fmt;
>  
>  	/* xor both blocks in one run */
>  	b1 = (unsigned long *) vsie_page->crycb.dea_wrapping_key_mask;
> 

This is wrong. I remember that with APXA, if FORMAT2 is available, we
should always use FORMAT2. That's why we explicitly convert it here.

-- 

Thanks,

David / dhildenb