From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 29EEAC54EBC for ; Wed, 11 Jan 2023 13:39:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239246AbjAKNjZ (ORCPT ); Wed, 11 Jan 2023 08:39:25 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33060 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239209AbjAKNjH (ORCPT ); Wed, 11 Jan 2023 08:39:07 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0FBEB1ADAD for ; Wed, 11 Jan 2023 05:36:40 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id C501BB81BE6 for ; Wed, 11 Jan 2023 13:36:38 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6BAE8C433EF; Wed, 11 Jan 2023 13:36:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1673444197; bh=jmhq9ChkH2NfqzWnvmpx3kh3Vnp+p3wr2mRMyDf+7DI=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=bU0z/WMfvYKXzmujZknAssAgPbjR1WKv89ti7YI8qpGJLQ/8EpzUjf7wm5/JQw7sa OFsj129pM1cvw618L1MZAWFc7kuB7WmqjIGVjVSTyCNK2jb84kADMAQdzBuY9z+d+g z9bCmRt1aegtA4sbUlNJ37wwrMX4NOKoE06XhPe1Zt2ierjC/vcfdaXM15uOtAnatT dHVnZkw3BYZ8Q3cHlgl7iqUMHzEHv06LP9AJXVEEaIP2V85J5OGXSp9juuORbArXjL rWLj61/n+bskBJny2Rf/noHUdFprxkM3zAgWyRjE8Aixd4B3ZkvoRYvthrGFgrcPz5 SEOkPs4uUs+KQ== Received: from disco-boy.misterjones.org ([51.254.78.96] helo=www.loen.fr) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.95) (envelope-from ) id 1pFbHO-000sOo-Vh; Wed, 11 Jan 2023 13:36:35 +0000 MIME-Version: 1.0 Date: Wed, 11 Jan 2023 13:36:34 +0000 From: Marc Zyngier To: Ganapatrao Kulkarni Cc: catalin.marinas@arm.com, will@kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org, scott@os.amperecomputing.com, Darren Hart Subject: Re: [PATCH 0/3] KVM: arm64: nv: Fixes for Nested Virtualization issues In-Reply-To: References: <20220824060304.21128-1-gankulkarni@os.amperecomputing.com> <6171dc7c-5d83-d378-db9e-d94f27afe43a@os.amperecomputing.com> <87o7r6dpi8.wl-maz@kernel.org> <4d952300-0681-41ff-b416-38fbae4ebea6@os.amperecomputing.com> <2169cc83d3015727f5f486844c8c4647@kernel.org> User-Agent: Roundcube Webmail/1.4.13 Message-ID: X-Sender: maz@kernel.org Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-SA-Exim-Connect-IP: 51.254.78.96 X-SA-Exim-Rcpt-To: gankulkarni@os.amperecomputing.com, catalin.marinas@arm.com, will@kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org, scott@os.amperecomputing.com, darren@os.amperecomputing.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On 2023-01-11 12:46, Ganapatrao Kulkarni wrote: > On 11-01-2023 05:09 pm, Marc Zyngier wrote: >> On 2023-01-11 08:46, Ganapatrao Kulkarni wrote: >>> On 11-01-2023 03:24 am, Marc Zyngier wrote: >>>> On Tue, 10 Jan 2023 12:17:20 +0000, >>>> Ganapatrao Kulkarni wrote: >>>>> >>>>> I am currently working around this with "nohlt" kernel param to >>>>> NestedVM. Any suggestions to handle/fix this case/issue and avoid >>>>> the >>>>> slowness of booting of NestedVM with more cores? >>>>> >>>>> Note: Guest-Hypervisor and NestedVM are using default kernel >>>>> installed >>>>> using Fedora 36 iso. >>>> >>>> Despite what I said earlier, I have a vague idea here, thanks to the >>>> interesting call traces that you provided (this is really awesome >>>> work >>>> BTW, given how hard it is to trace things across 3 different >>>> kernels). >>>> >>>> We can slightly limit the impact of the prepare/finish sequence if >>>> the >>>> guest hypervisor only accesses the active registers for SGIs/PPIs on >>>> the vcpu that owns them, forbidding any cross-CPU-to-redistributor >>>> access. >>>> >>>> Something along these lines, which is only boot-tested. Let me know >>>> how this fares for you. >>>> >>>> Thanks, >>>> >>>>     M. >>>> >>>> diff --git a/arch/arm64/kvm/vgic/vgic-mmio.c >>>> b/arch/arm64/kvm/vgic/vgic-mmio.c >>>> index b32d434c1d4a..1cca45be5335 100644 >>>> --- a/arch/arm64/kvm/vgic/vgic-mmio.c >>>> +++ b/arch/arm64/kvm/vgic/vgic-mmio.c >>>> @@ -473,9 +473,10 @@ int vgic_uaccess_write_cpending(struct kvm_vcpu >>>> *vcpu, >>>>    * active state can be overwritten when the VCPU's state is synced >>>> coming back >>>>    * from the guest. >>>>    * >>>> - * For shared interrupts as well as GICv3 private interrupts, we >>>> have to >>>> - * stop all the VCPUs because interrupts can be migrated while we >>>> don't hold >>>> - * the IRQ locks and we don't want to be chasing moving targets. >>>> + * For shared interrupts as well as GICv3 private interrupts >>>> accessed from the >>>> + * non-owning CPU, we have to stop all the VCPUs because interrupts >>>> can be >>>> + * migrated while we don't hold the IRQ locks and we don't want to >>>> be chasing >>>> + * moving targets. >>>>    * >>>>    * For GICv2 private interrupts we don't have to do anything >>>> because >>>>    * userspace accesses to the VGIC state already require all VCPUs >>>> to be >>>> @@ -484,7 +485,8 @@ int vgic_uaccess_write_cpending(struct kvm_vcpu >>>> *vcpu, >>>>    */ >>>>   static void vgic_access_active_prepare(struct kvm_vcpu *vcpu, u32 >>>> intid) >>>>   { >>>> -    if (vcpu->kvm->arch.vgic.vgic_model == KVM_DEV_TYPE_ARM_VGIC_V3 >>>> || >>>> +    if ((vcpu->kvm->arch.vgic.vgic_model == >>>> KVM_DEV_TYPE_ARM_VGIC_V3 && >>>> +         vcpu == kvm_get_running_vcpu()) || >>> >>> Thanks Marc for the patch! >>> >>> I think, you mean not equal to? >>> +           vcpu != kvm_get_running_vcpu()) || >> >> Yeah, exactly. I woke up this morning realising this patch was >> *almost* right. Don't write patches like this after a long day >> at work... >> >>> With the change to not-equal, the issue is fixed and I could see the >>> NestedVM booting is pretty fast with higher number of cores as well. >> >> Good, thanks for testing it. I'll roll up an actual patch for that >> and stick it in the monster queue. > > Thanks, Please pull patch 3/3 also to nv-6.2 tree along with this > patch. I will move my setup to nv-6.2 once these patches are in. 3/3 should already be in the branch, merged with the shadow S2 fault handling. M. -- Jazz is not dead. It just smells funny...