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Tue, 21 Jan 2020 16:12:30 +0000 (UTC) Date: Tue, 21 Jan 2020 17:12:28 +0100 From: Cornelia Huck To: Matthew Rosato , Thomas Huth Subject: Re: [PATCH v3] target/s390x/kvm: Enable adapter interruption suppression again Message-ID: <20200121171228.3d04cf3c.cohuck@redhat.com> In-Reply-To: <91bed750-8b12-4f9a-ff57-57fd23fc11ca@linux.ibm.com> References: <20200120132441.11884-1-thuth@redhat.com> <20200120182747.5135fea8.cohuck@redhat.com> <95fa3c7d-8879-1401-6847-c5fa82a0cd3c@linux.ibm.com> <20200121154608.0b043233.cohuck@redhat.com> <6eceafc9-afb5-05a7-0713-2295886f6917@redhat.com> <91bed750-8b12-4f9a-ff57-57fd23fc11ca@linux.ibm.com> Organization: Red Hat GmbH MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-MC-Unique: pm0_cc2cPSKL4jPBa89Ncw-1 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 205.139.110.120 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Halil Pasic , Christian Borntraeger , qemu-s390x@nongnu.org, qemu-devel@nongnu.org, David Hildenbrand Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Tue, 21 Jan 2020 11:05:18 -0500 Matthew Rosato wrote: > On 1/21/20 10:22 AM, Thomas Huth wrote: > > On 21/01/2020 15.46, Cornelia Huck wrote: > >> On Tue, 21 Jan 2020 09:33:02 -0500 > >> Matthew Rosato wrote: > >> > >>> On 1/20/20 12:27 PM, Cornelia Huck wrote: > >>>> On Mon, 20 Jan 2020 14:24:41 +0100 > >>>> Thomas Huth wrote: > >>>> > >>>>> The AIS feature has been disabled late in the v2.10 development cycle since > >>>>> there were some issues with migration (see commit 3f2d07b3b01ea61126b - > >>>>> "s390x/ais: for 2.10 stable: disable ais facility"). We originally wanted > >>>>> to enable it again for newer machine types, but apparently we forgot to do > >>>>> this so far. Let's do it for the new s390-ccw-virtio-5.0 machine now. > >>>>> > >>>>> While at it, also add a more verbose comment why we need the *_allowed() > >>>>> wrappers in s390-virtio-ccw.c. > >>>>> > >>>>> Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=1756946 > >>>>> Reviewed-by: David Hildenbrand > >>>>> Signed-off-by: Thomas Huth > >>>>> --- > >>>>> v3: Moved "s390mc->kvm_ais_allowed = false" to the end of the function > >>>>> > >>>>> hw/s390x/s390-virtio-ccw.c | 20 +++++++++++++++++--- > >>>>> include/hw/s390x/s390-virtio-ccw.h | 3 +++ > >>>>> target/s390x/kvm.c | 9 ++++++--- > >>>>> 3 files changed, 26 insertions(+), 6 deletions(-) > >>>> > >>>>> diff --git a/target/s390x/kvm.c b/target/s390x/kvm.c > >>>>> index 15260aeb9a..cf4fb4f2d9 100644 > >>>>> --- a/target/s390x/kvm.c > >>>>> +++ b/target/s390x/kvm.c > >>>>> @@ -365,10 +365,13 @@ int kvm_arch_init(MachineState *ms, KVMState *s) > >>>>> /* > >>>>> * The migration interface for ais was introduced with kernel 4.13 > >>>>> * but the capability itself had been active since 4.12. As migration > >>>>> - * support is considered necessary let's disable ais in the 2.10 > >>>>> - * machine. > >>>>> + * support is considered necessary, we only try to enable this for > >>>>> + * newer machine types if KVM_CAP_S390_AIS_MIGRATION is available. > >>>>> */ > >>>>> - /* kvm_vm_enable_cap(s, KVM_CAP_S390_AIS, 0); */ > >>>>> + if (kvm_ais_allowed() && > >>>>> + kvm_check_extension(s, KVM_CAP_S390_AIS_MIGRATION)) { > >>>> > >>>> Hnm, we actually need a kernel irqchip with the kvm flic to get ais to > >>>> work; else we'll fail with > >>>> > >>>> qemu-system-s390x: Failed to inject airq with AIS supported > >>>> > >>>> in the kernel_irqchip=off case, as we won't have an I/O adapter > >>>> registered. > >>>> > >>>> Adding 'kvm_kernel_irqchip_required() &&' seems to do the trick; > >>>> comments? > >>>> > >>> > >>> In spirit, I agree with this idea. But, a quick test shows that putting > >>> this check here results in ais=off for the 'none' machine case (libvirt > >>> capabilities detection). I think we have to only look at > >>> kvm_kernel_irqchip_required() when working with a real machine. > >> > >> Sigh, I think you're right again. We need to check for the 'none' > >> machine here; but I can't think of a non-ugly way to do so... > > > > I think it might work when using kvm_kernel_irqchip_allowed() instead of > > kvm_kernel_irqchip_required() ... Matthew, could you please give it a > > try with this patch on top of mine: > > > > Sure. > > Libvirt detection works with this patch. Excellent. > > Alternatively, if I run qemu with kernel_irqchip=off and ais=true, I get: > qemu-system-s390x: Some features requested in the CPU model are not > available in the configuration: ais > > Which was the same result as Connie's proposal. Yep, that's the expected behaviour. > > It reads a bit odd to me at first, but looking at the code quick I think > this is the right answer - kvm_kernel_irqchip_allowed() will only return > false when kernel_irqchip has been forced off as above, whereas > kernel_irqchip_required will also return false in the case where no > setting was specified (this is what tripped libvirt up). > > Looks good to me, thanks Thomas. Thanks for testing! Thomas, I guess you'll send a v4?