linux-kernel - Re: [RFC PATCH v1 02/10] KVM: s390: Honor storage keys when accessing guest memory

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Message-ID: <6d3a4e4e-a038-0a30-6846-3f07948dab08@linux.ibm.com>
Date:   Thu, 20 Jan 2022 11:30:08 +0100
From:   Janis Schoetterl-Glausch <scgl@...ux.ibm.com>
To:     Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Janosch Frank <frankja@...ux.ibm.com>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        David Hildenbrand <david@...hat.com>
Cc:     Claudio Imbrenda <imbrenda@...ux.ibm.com>,
        linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org
Subject: Re: [RFC PATCH v1 02/10] KVM: s390: Honor storage keys when accessing
 guest memory

On 1/20/22 11:27, Christian Borntraeger wrote:
> 
> 
> Am 18.01.22 um 15:38 schrieb Janosch Frank:
> [...]
>> /*
>> We'll do an actual access via the mv instruction which will return access errors to us so we don't need to check here.
>> */
> 
> Be slightly more verbose I guess. Something like
> We'll do an actual access via the mv instruction which will return access errors to us so we don't need to check here.
> By using key 0 all checks are skipped and no performance overhead occurs.
> 
> ?

Yes, I'll also mention that we implement storage protection override by retrying.
> 
>>> +    rc = guest_range_to_gpas(vcpu, ga, ar, gpas, len, asce, mode, 0);