From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754932AbeDWLvN (ORCPT ); Mon, 23 Apr 2018 07:51:13 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:50420 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754837AbeDWLu4 (ORCPT ); Mon, 23 Apr 2018 07:50:56 -0400 Subject: Re: [PATCH v2] KVM: Extend MAX_IRQ_ROUTES to 4096 for all archs To: Wanpeng Li , Cornelia Huck Cc: LKML , kvm , Paolo Bonzini , =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= , Tonny Lu , Janosch Frank References: <1524185248-51744-1-git-send-email-wanpengli@tencent.com> <20180420091537.1c6cb06b.cohuck@redhat.com> <20180420162155.675d516d.cohuck@redhat.com> From: Christian Borntraeger Openpgp: preference=signencrypt Date: Mon, 23 Apr 2018 13:50:48 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 x-cbid: 18042311-0044-0000-0000-0000054B2E20 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18042311-0045-0000-0000-0000288B5A8F Message-Id: <38e7d755-f95a-fcad-3f70-3a4eb049fc81@de.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2018-04-23_05:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1011 lowpriorityscore=0 impostorscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1709140000 definitions=main-1804230123 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/21/2018 02:38 AM, Wanpeng Li wrote: > 2018-04-20 22:21 GMT+08:00 Cornelia Huck : >> On Fri, 20 Apr 2018 21:51:13 +0800 >> Wanpeng Li wrote: >> >>> 2018-04-20 15:15 GMT+08:00 Cornelia Huck : >>>> On Thu, 19 Apr 2018 17:47:28 -0700 >>>> Wanpeng Li wrote: >>>> >>>>> From: Wanpeng Li >>>>> >>>>> 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 >>>>> Cc: Radim Krčmář >>>>> Cc: Tonny Lu >>>>> Cc: Cornelia Huck >>>>> Signed-off-by: Wanpeng Li >>>>> Signed-off-by: Tonny Lu >>>>> --- >>>>> 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.