linux-kernel - Re: [PATCH] KVM: s390: Do not leak kernel stack data in the KVM_S390

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Message-ID: <ed0cf9eb-e3dc-f8d5-1eea-9034e5c0498d@redhat.com>
Date:   Fri, 13 Sep 2019 09:34:34 +0200
From:   Thomas Huth <thuth@...hat.com>
To:     Cornelia Huck <cohuck@...hat.com>
Cc:     Christian Borntraeger <borntraeger@...ibm.com>,
        David Hildenbrand <david@...hat.com>,
        Janosch Frank <frankja@...ux.ibm.com>, kvm@...r.kernel.org,
        linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] KVM: s390: Do not leak kernel stack data in the
 KVM_S390_INTERRUPT ioctl

On 13/09/2019 09.20, Cornelia Huck wrote:
> On Thu, 12 Sep 2019 13:23:38 +0200
> Thomas Huth <thuth@...hat.com> wrote:
> 
>> Hmm, we already talked about deprecating support for pre-3.15 kernel
>> stuff in the past (see
>> https://wiki.qemu.org/ChangeLog/2.12#Future_incompatible_changes for
>> example),
> 
> Btw: did we ever do that? I don't quite recall what code we were
> talking about...

We never really did - but we also never fixed the issue: If you run the
current QEMU on a kernel before 3.15, it refuses to work due to the
missing in-kernel FLIC device:

Initialization of device s390-flic-kvm failed: KVM is missing capability
KVM_CAP_DEVICE_CTR

Since nobody really complained so far that running QEMU with KVM is
still required on a kernel < 3.15, I think we could make this also
"official" now and improve the error message a little bit, pointing the
user to a kernel >= 3.15.

 Thomas