On Mon, 23 Apr 2018 13:50:48 +0200 Christian Borntraeger <borntrae...@de.ibm.com> wrote:
> On 04/21/2018 02:38 AM, Wanpeng Li wrote: > > 2018-04-20 22:21 GMT+08:00 Cornelia Huck <coh...@redhat.com>: > >> On Fri, 20 Apr 2018 21:51:13 +0800 > >> Wanpeng Li <kernel...@gmail.com> wrote: > >> > >>> 2018-04-20 15:15 GMT+08:00 Cornelia Huck <coh...@redhat.com>: > >>>> On Thu, 19 Apr 2018 17:47:28 -0700 > >>>> Wanpeng Li <kernel...@gmail.com> wrote: > >>>> > >>>>> From: Wanpeng Li <wanpen...@tencent.com> > >>>>> > >>>>> Our virtual machines make use of device assignment by configuring > >>>>> 12 NVMe disks for high I/O performance. Each NVMe device has 129 > >>>>> MSI-X Table entries: > >>>>> Capabilities: [50] MSI-X: Enable+ Count=129 Masked-Vector table: BAR=0 > >>>>> offset=00002000 > >>>>> The windows virtual machines fail to boot since they will map the > >>>>> number of > >>>>> MSI-table entries that the NVMe hardware reported to the bus to msi > >>>>> routing > >>>>> table, this will exceed the 1024. This patch extends MAX_IRQ_ROUTES to > >>>>> 4096 > >>>>> for all archs, in the future this might be extended again if needed. > >>>>> > >>>>> Cc: Paolo Bonzini <pbonz...@redhat.com> > >>>>> Cc: Radim Krčmář <rkrc...@redhat.com> > >>>>> Cc: Tonny Lu <tonn...@tencent.com> > >>>>> Cc: Cornelia Huck <coh...@redhat.com> > >>>>> Signed-off-by: Wanpeng Li <wanpen...@tencent.com> > >>>>> Signed-off-by: Tonny Lu <tonn...@tencent.com> > >>>>> --- > >>>>> v1 -> v2: > >>>>> * extend MAX_IRQ_ROUTES to 4096 for all archs > >>>>> > >>>>> include/linux/kvm_host.h | 6 ------ > >>>>> 1 file changed, 6 deletions(-) > >>>>> > >>>>> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h > >>>>> index 6930c63..0a5c299 100644 > >>>>> --- a/include/linux/kvm_host.h > >>>>> +++ b/include/linux/kvm_host.h > >>>>> @@ -1045,13 +1045,7 @@ static inline int mmu_notifier_retry(struct kvm > >>>>> *kvm, unsigned long mmu_seq) > >>>>> > >>>>> #ifdef CONFIG_HAVE_KVM_IRQ_ROUTING > >>>>> > >>>>> -#ifdef CONFIG_S390 > >>>>> #define KVM_MAX_IRQ_ROUTES 4096 //FIXME: we can have more than that... > >>>>> > >>>> > >>>> What about /* might need extension/rework in the future */ instead of > >>>> the FIXME? > >>> > >>> Yeah, I guess the maintainers can help to fix it when applying. :) > >>> > >>>> > >>>> As far as I understand, 4096 should cover most architectures and the > >>>> sane end of s390 configurations, but will not be enough at the scarier > >>>> end of s390. (I'm not sure how much it matters in practice.) > >>>> > >>>> Do we want to make this a tuneable in the future? Do some kind of > >>>> dynamic allocation? Not sure whether it is worth the trouble. > >>> > >>> I think keep as it is currently. > >> > >> My main question here is how long this is enough... the number of > >> virtqueues per device is up to 1K from the initial 64, which makes it > >> possible to hit the 4K limit with fewer virtio devices than before (on > >> s390, each virtqueue uses a routing table entry). OTOH, we don't want > >> giant tables everywhere just to accommodate s390. > > > > I suspect there is no real scenario to futher extend for s390 since no > > guys report. > > > >> If the s390 maintainers tell me that nobody is doing the really insane > >> stuff, I'm happy as well :) > > > > Christian, any thoughts? > > For now this patch is a no-op for s390 so as long as nobody complains today > we are good. > If it turns out to be "not enough" we can then add a configurable number or > whatever. OK, then let's deal with the problem once it shows up. With the comment changed as suggested above, Reviewed-by: Cornelia Huck <coh...@redhat.com>
