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[209.132.180.67]) by mx.google.com with ESMTP id n26si3530100pgv.264.2019.06.21.15.11.44; Fri, 21 Jun 2019 15:12:00 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726244AbfFUWLk (ORCPT + 99 others); Fri, 21 Jun 2019 18:11:40 -0400 Received: from mx1.redhat.com ([209.132.183.28]:43198 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726031AbfFUWLk (ORCPT ); Fri, 21 Jun 2019 18:11:40 -0400 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id D004A882F2; Fri, 21 Jun 2019 22:11:39 +0000 (UTC) Received: from amt.cnet (ovpn-112-4.gru2.redhat.com [10.97.112.4]) by smtp.corp.redhat.com (Postfix) with ESMTP id 4B30F60BFB; Fri, 21 Jun 2019 22:11:39 +0000 (UTC) Received: from amt.cnet (localhost [127.0.0.1]) by amt.cnet (Postfix) with ESMTP id F3863105169; Fri, 21 Jun 2019 18:42:11 -0300 (BRT) Received: (from marcelo@localhost) by amt.cnet (8.14.7/8.14.7/Submit) id x5LLg7R6005552; Fri, 21 Jun 2019 18:42:07 -0300 Date: Fri, 21 Jun 2019 18:42:06 -0300 From: Marcelo Tosatti To: Wanpeng Li Cc: Paolo Bonzini , LKML , kvm , Radim =?utf-8?B?S3LEjW3DocWZ?= Subject: Re: [PATCH v4 2/5] KVM: LAPIC: inject lapic timer interrupt by posted interrupt Message-ID: <20190621214205.GA4751@amt.cnet> References: <1560770687-23227-1-git-send-email-wanpengli@tencent.com> <1560770687-23227-3-git-send-email-wanpengli@tencent.com> <20190618133541.GA3932@amt.cnet> <20190619210346.GA13033@amt.cnet> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.28]); Fri, 21 Jun 2019 22:11:39 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jun 21, 2019 at 09:42:39AM +0800, Wanpeng Li wrote: > On Thu, 20 Jun 2019 at 05:04, Marcelo Tosatti wrote: > > > > Hi Li, > > > > On Wed, Jun 19, 2019 at 08:36:06AM +0800, Wanpeng Li wrote: > > > On Tue, 18 Jun 2019 at 21:36, Marcelo Tosatti wrote: > > > > > > > > On Mon, Jun 17, 2019 at 07:24:44PM +0800, Wanpeng Li wrote: > > > > > From: Wanpeng Li > > > > > > > > > > Dedicated instances are currently disturbed by unnecessary jitter due > > > > > to the emulated lapic timers fire on the same pCPUs which vCPUs resident. > > > > > There is no hardware virtual timer on Intel for guest like ARM. Both > > > > > programming timer in guest and the emulated timer fires incur vmexits. > > > > > This patch tries to avoid vmexit which is incurred by the emulated > > > > > timer fires in dedicated instance scenario. > > > > > > > > > > When nohz_full is enabled in dedicated instances scenario, the emulated > > > > > timers can be offload to the nearest busy housekeeping cpus since APICv > > > > > is really common in recent years. The guest timer interrupt is injected > > > > > by posted-interrupt which is delivered by housekeeping cpu once the emulated > > > > > timer fires. > > > > > > > > > > The host admin should fine tuned, e.g. dedicated instances scenario w/ > > > > > nohz_full cover the pCPUs which vCPUs resident, several pCPUs surplus > > > > > for busy housekeeping, disable mwait/hlt/pause vmexits to keep in non-root > > > > > mode, ~3% redis performance benefit can be observed on Skylake server. > > > > > > > > > > w/o patch: > > > > > > > > > > VM-EXIT Samples Samples% Time% Min Time Max Time Avg time > > > > > > > > > > EXTERNAL_INTERRUPT 42916 49.43% 39.30% 0.47us 106.09us 0.71us ( +- 1.09% ) > > > > > > > > > > w/ patch: > > > > > > > > > > VM-EXIT Samples Samples% Time% Min Time Max Time Avg time > > > > > > > > > > EXTERNAL_INTERRUPT 6871 9.29% 2.96% 0.44us 57.88us 0.72us ( +- 4.02% ) > > > > > > > > > > Cc: Paolo Bonzini > > > > > Cc: Radim Krčmář > > > > > Cc: Marcelo Tosatti > > > > > Signed-off-by: Wanpeng Li > > > > > --- > > > > > arch/x86/kvm/lapic.c | 33 ++++++++++++++++++++++++++------- > > > > > arch/x86/kvm/lapic.h | 1 + > > > > > arch/x86/kvm/vmx/vmx.c | 3 ++- > > > > > arch/x86/kvm/x86.c | 5 +++++ > > > > > arch/x86/kvm/x86.h | 2 ++ > > > > > include/linux/sched/isolation.h | 2 ++ > > > > > kernel/sched/isolation.c | 6 ++++++ > > > > > 7 files changed, 44 insertions(+), 8 deletions(-) > > > > > > > > > > diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c > > > > > index 87ecb56..9ceeee5 100644 > > > > > --- a/arch/x86/kvm/lapic.c > > > > > +++ b/arch/x86/kvm/lapic.c > > > > > @@ -122,6 +122,13 @@ static inline u32 kvm_x2apic_id(struct kvm_lapic *apic) > > > > > return apic->vcpu->vcpu_id; > > > > > } > > > > > > > > > > +bool posted_interrupt_inject_timer(struct kvm_vcpu *vcpu) > > > > > +{ > > > > > + return pi_inject_timer && kvm_vcpu_apicv_active(vcpu) && > > > > > + kvm_hlt_in_guest(vcpu->kvm); > > > > > +} > > > > > +EXPORT_SYMBOL_GPL(posted_interrupt_inject_timer); > > > > > > > > Paolo, can you explain the reasoning behind this? > > > > > > > > Should not be necessary... > > https://lkml.org/lkml/2019/6/5/436 "Here you need to check > kvm_halt_in_guest, not kvm_mwait_in_guest, because you need to go > through kvm_apic_expired if the guest needs to be woken up from > kvm_vcpu_block." Ah, i think he means that a sleeping vcpu (in kvm_vcpu_block) must be woken up, if it receives a timer interrupt. But your patch will go through: kvm_apic_inject_pending_timer_irqs __apic_accept_irq -> vmx_deliver_posted_interrupt -> kvm_vcpu_trigger_posted_interrupt returns false (because vcpu->mode != IN_GUEST_MODE) -> kvm_vcpu_kick Which will wakeup the vcpu. Apart from this oops, which triggers when running: taskset -c 1 ./cyclictest -D 3600 -p 99 -t 1 -h 30 -m -n -i 50000 -b 40 Timer interruption from housekeeping vcpus is normal to me (without requiring kvm_hlt_in_guest). [ 1145.849646] BUG: kernel NULL pointer dereference, address: 0000000000000000 [ 1145.850481] #PF: supervisor instruction fetch in kernel mode [ 1145.851161] #PF: error_code(0x0010) - not-present page [ 1145.851772] PGD 80000002a9fa5067 P4D 80000002a9fa5067 PUD 2abcbb067 PMD 0 [ 1145.852578] Oops: 0010 [#1] PREEMPT SMP PTI [ 1145.853066] CPU: 2 PID: 0 Comm: swapper/2 Not tainted 5.2.0-rc1+ #11 [ 1145.853809] Hardware name: Red Hat KVM, BIOS 1.11.0-2.el7 04/01/2014 [ 1145.854554] RIP: 0010:0x0 [ 1145.854879] Code: Bad RIP value. [ 1145.855270] RSP: 0018:ffffc90001903e68 EFLAGS: 00010013 [ 1145.855902] RAX: 0000010ac9f60043 RBX: ffff8882b58a8320 RCX: 00000000c526b7c4 [ 1145.856726] RDX: 0000000000000000 RSI: ffffffff820d9640 RDI: ffff8882b58a8320 [ 1145.857560] RBP: ffffffff820d9640 R08: 00000000c526b7c4 R09: 0000000000000832 [ 1145.858390] R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 [ 1145.859222] R13: ffffffff820d9658 R14: ffff8881063b2880 R15: 0000000000000002 [ 1145.860047] FS: 0000000000000000(0000) GS:ffff8882b5880000(0000) knlGS:0000000000000000 [ 1145.860994] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 1145.861692] CR2: ffffffffffffffd6 CR3: 00000002ab1de001 CR4: 0000000000160ee0 [ 1145.862570] Call Trace: [ 1145.862877] cpuidle_enter_state+0x7c/0x3e0 [ 1145.863392] cpuidle_enter+0x29/0x40 > I think we can still be woken up from kvm_vcpu_block() if pir is set. Exactly.