linux-kernel - Re: [PATCH v3 2/3] KVM: s390: vsie: Do the CRYCB validation first

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Message-Id: <b7c0b0eb-c750-caeb-41b5-d6593791a6ef@de.ibm.com>
Date:   Thu, 23 Aug 2018 13:17:47 +0200
From:   Christian Borntraeger <borntraeger@...ibm.com>
To:     Pierre Morel <pmorel@...ux.ibm.com>, david@...hat.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,
        schwidefsky@...ibm.com, heiko.carstens@...ibm.com
Subject: Re: [PATCH v3 2/3] KVM: s390: vsie: Do the CRYCB validation first



On 08/23/2018 12:25 PM, Pierre Morel wrote:
> When entering the SIE the CRYCB validation better
> be done independently of the instruction's
> availability.

Maybe something like

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.

?

> 
> Signed-off-by: Pierre Morel <pmorel@...ux.ibm.com>
> ---
>  arch/s390/kvm/vsie.c | 11 ++++++-----
>  1 file changed, 6 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/s390/kvm/vsie.c b/arch/s390/kvm/vsie.c
> index 12b9707..38ea5da 100644
> --- a/arch/s390/kvm/vsie.c
> +++ b/arch/s390/kvm/vsie.c
> @@ -161,17 +161,18 @@ static int shadow_crycb(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
>  	/* format-1 is supported with message-security-assist extension 3 */
>  	if (!test_kvm_facility(vcpu->kvm, 76))
>  		return 0;
> -	/* we may only allow it if enabled for guest 2 */
> -	ecb3_flags = scb_o->ecb3 & vcpu->arch.sie_block->ecb3 &
> -		     (ECB3_AES | ECB3_DEA);
> -	if (!ecb3_flags)
> -		return 0;
> 
>  	if ((crycb_addr & PAGE_MASK) != ((crycb_addr + 128) & PAGE_MASK))
>  		return set_validity_icpt(scb_s, 0x003CU);
>  	else if (!crycb_addr)
>  		return set_validity_icpt(scb_s, 0x0039U);
> 
> +	/* we may only allow it if enabled for guest 2 */
> +	ecb3_flags = scb_o->ecb3 & vcpu->arch.sie_block->ecb3 &
> +		     (ECB3_AES | ECB3_DEA);
> +	if (!ecb3_flags)
> +		return 0;
> +
>  	/* copy only the wrapping keys */
>  	if (read_guest_real(vcpu, crycb_addr + 72,
>  			    vsie_page->crycb.dea_wrapping_key_mask, 56))
>