linux-kernel - Re: [PATCH v2 0/2] Dirtying, failing memop: don't indicate suppression

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Message-ID: <385126e7-b74b-1826-c134-3efd278e5b79@linux.ibm.com>
Date:   Mon, 2 May 2022 09:58:38 +0200
From:   Christian Borntraeger <borntraeger@...ux.ibm.com>
To:     Janosch Frank <frankja@...ux.ibm.com>,
        Janis Schoetterl-Glausch <scgl@...ux.ibm.com>,
        Claudio Imbrenda <imbrenda@...ux.ibm.com>
Cc:     David Hildenbrand <david@...hat.com>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Sven Schnelle <svens@...ux.ibm.com>,
        Paolo Bonzini <pbonzini@...hat.com>, kvm@...r.kernel.org,
        Shuah Khan <shuah@...nel.org>, linux-kselftest@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org
Subject: Re: [PATCH v2 0/2] Dirtying, failing memop: don't indicate
 suppression

Am 26.04.22 um 09:25 schrieb Janosch Frank:
> 
> To me this measure looks like a last resort option and the POP doesn't state a 100% what is to be done. Some instructions can mandate suppression instead of termination according to the architects.
> 
> My intuition tells me that if we are in a situation where this would happen then we would be much better off just doing it by hand (i.e. in the instruction emulation code) and not letting this function decide.
> 
> So I'm not entirely sure if we're replacing something that is not correct with something that also won't be correct for all cases.
> 
> But to summarize this: I'm not entirely sure even after reading the POP for more than an hour and consulting an architect

According to Damian, the definition in the POP is exactly the way it is to cover for z/VMs way of handling key protection for long operatings in a terminating fashion since the 70ies or 80ies.
As it is fine for z/VM (and then also for z/OS and zVSE under z/VM) I guess we can (and should) mimic that behaviour.