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Message-ID: <39c529db-e7bd-c216-62b7-773a51d919b6@linux.ibm.com>
Date:   Wed, 19 Jan 2022 14:17:43 +0100
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Subject: Re: [RFC PATCH v1 06/10] KVM: s390: Add vm IOCTL for key checked
 guest absolute memory access
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To:     Thomas Huth <thuth@redhat.com>,
        Christian Borntraeger <borntraeger@linux.ibm.com>,
        Janosch Frank <frankja@linux.ibm.com>,
        Heiko Carstens <hca@linux.ibm.com>,
        Vasily Gorbik <gor@linux.ibm.com>
Cc:     David Hildenbrand <david@redhat.com>,
        Claudio Imbrenda <imbrenda@linux.ibm.com>,
        Alexander Gordeev <agordeev@linux.ibm.com>,
        kvm@vger.kernel.org, linux-s390@vger.kernel.org,
        linux-kernel@vger.kernel.org
References: <20220118095210.1651483-1-scgl@linux.ibm.com>
 <20220118095210.1651483-7-scgl@linux.ibm.com>
 <a3a143f8-8fd5-49bf-9b2b-2f7cb04732de@redhat.com>
 <8d09dc2e-2d2d-e5f6-8cc7-eecfc94a17b2@linux.ibm.com>
 <cd79f893-c711-1a60-47d6-7c392e02fc6a@redhat.com>
From:   Janis Schoetterl-Glausch <scgl@linux.ibm.com>
In-Reply-To: <cd79f893-c711-1a60-47d6-7c392e02fc6a@redhat.com>
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On 1/19/22 13:53, Thomas Huth wrote:
> On 19/01/2022 13.46, Christian Borntraeger wrote:
>>
>>
>> Am 19.01.22 um 12:52 schrieb Thomas Huth:
>>> On 18/01/2022 10.52, Janis Schoetterl-Glausch wrote:
>>>> Channel I/O honors storage keys and is performed on absolute memory.
>>>> For I/O emulation user space therefore needs to be able to do key
>>>> checked accesses.
>>>
>>> Can't we do the checking in userspace? We already have functions for handling the storage keys there (see hw/s390x/s390-skeys-kvm.c), so why can't we do the checking in QEMU?
>>
>> That would separate the key check from the memory operation. Potentially for a long time.
>> Wenn we piggy back on access_guest_abs_with_key we use mvcos in the host and thus do the key check in lockstep with the keycheck which is the preferrable solution.
> 
> Ok, makes sense - Janis, could you please add this rationale to the patch description?

Will do.
> 
>  Thomas
>