From: David Hildenbrand <david@redhat.com>
To: Christian Borntraeger <borntraeger@de.ibm.com>,
Collin Walling <walling@linux.ibm.com>,
pbonzini@redhat.com, cohuck@redhat.com,
linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-s390@vger.kernel.org
Cc: schwidefsky@de.ibm.com, heiko.carstens@de.ibm.com, frankja@linux.ibm.com
Subject: Re: [PATCH v3 1/2] s390/setup: diag318: remove bit check and refactor struct
Date: Wed, 3 Apr 2019 14:09:14 +0200 [thread overview]
Message-ID: <13072d30-0ecb-e655-8f34-71c640a519df@redhat.com> (raw)
In-Reply-To: <92d69cf5-0510-cf22-9f72-ab3efe4ede9b@de.ibm.com>
On 03.04.19 13:28, Christian Borntraeger wrote:
>
>
> On 02.04.19 19:46, Collin Walling wrote:
>> Execution of DIAGNOSE 0x318 is fenced by checking an SCLP bit
>> for the availability of hardware support for the instruction.
>>
>> In order to support this instruction for a KVM/QEMU guest, we
>> would need to provide modifications to the SCLP Read SCP Info
>> data, which will in turn reduce the maximum number of CPUs that
>> may be provided to the guest. This issue introduces compatability
>> and legacy concerns.
>>
>> Let's circumvent this issue by removing the bit check and blindly
>> executing the instruction. An exception table rule is in place to
>> catch the case where hardware does not support this instruction.
>
>
> No, please keep the check. We have to extend the read scp field anyway
> for future extensions.
Wasn't there already an SCLP-way of telling the guest that the read-scp
info response is bigger than 4k? Somehow rings a bell ...
--
Thanks,
David / dhildenb
next prev parent reply other threads:[~2019-04-03 12:09 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-02 17:46 [PATCH v3 0/2] Use DIAG318 to set Control Program Name & Version Codes Collin Walling
2019-04-02 17:46 ` [PATCH v3 1/2] s390/setup: diag318: remove bit check and refactor struct Collin Walling
2019-04-03 6:36 ` Janosch Frank
2019-04-03 11:28 ` Christian Borntraeger
2019-04-03 12:09 ` David Hildenbrand [this message]
2019-04-03 12:10 ` Christian Borntraeger
2019-04-03 12:03 ` David Hildenbrand
2019-04-03 12:33 ` Cornelia Huck
2019-04-03 14:22 ` Collin Walling
2019-04-02 17:46 ` [PATCH v3 2/2] s390/kvm: diagnose 318 handling Collin Walling
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