linux-kernel - Re: [PATCH] KVM: s390: fix sthyi error handling

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Date:   Fri, 28 Jul 2023 16:29:14 +0200
From:   Christian Borntraeger <borntraeger@...ux.ibm.com>
To:     Heiko Carstens <hca@...ux.ibm.com>
Cc:     Janosch Frank <frankja@...ux.ibm.com>,
        Claudio Imbrenda <imbrenda@...ux.ibm.com>,
        David Hildenbrand <david@...hat.com>,
        Mete Durlu <meted@...ux.ibm.com>, kvm@...r.kernel.org,
        linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] KVM: s390: fix sthyi error handling



Am 28.07.23 um 11:14 schrieb Heiko Carstens:
> On Fri, Jul 28, 2023 at 09:28:58AM +0200, Christian Borntraeger wrote:
>> Am 27.07.23 um 20:29 schrieb Heiko Carstens:
>>> Commit 9fb6c9b3fea1 ("s390/sthyi: add cache to store hypervisor info")
>>> added cache handling for store hypervisor info. This also changed the
>>> possible return code for sthyi_fill().
>>>
>>> Instead of only returning a condition code like the sthyi instruction would
>>> do, it can now also return a negative error value (-ENOMEM). handle_styhi()
>>> was not changed accordingly. In case of an error, the negative error value
>>> would incorrectly injected into the guest PSW.
>>>
>>> Add proper error handling to prevent this, and update the comment which
>>> describes the possible return values of sthyi_fill().
>>
>> To me it looks like this can only happen if page allocation fails? This should
>> not happen in normal cases (and return -ENOMEM would likely kill the guest as
>> QEMU would stop).
>> But if it happens we better stop.
> 
> Yes, no reason for any stable backports. But things might change in the
> future, so we better have correct error handling in place.

Feel free to carry via the s390 tree.