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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id EE89AC433F5 for ; Thu, 28 Oct 2021 17:16:10 +0000 (UTC) Received: from mm01.cs.columbia.edu (mm01.cs.columbia.edu [128.59.11.253]) by mail.kernel.org (Postfix) with ESMTP id 8ECB2610E5 for ; Thu, 28 Oct 2021 17:16:10 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 8ECB2610E5 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=lists.cs.columbia.edu Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 4031F4B1D7; Thu, 28 Oct 2021 13:16:10 -0400 (EDT) X-Virus-Scanned: at lists.cs.columbia.edu Authentication-Results: mm01.cs.columbia.edu (amavisd-new); dkim=softfail (fail, message has been altered) header.i=@redhat.com Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id sIFPeXGphs6W; Thu, 28 Oct 2021 13:16:08 -0400 (EDT) Received: from mm01.cs.columbia.edu (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 1428D4B208; Thu, 28 Oct 2021 13:16:01 -0400 (EDT) Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id AB7CB4B1CA for ; Thu, 28 Oct 2021 12:13:05 -0400 (EDT) X-Virus-Scanned: at lists.cs.columbia.edu Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id Ftr1oxDHqmGw for ; Thu, 28 Oct 2021 12:13:04 -0400 (EDT) Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 6153E4B14C for ; Thu, 28 Oct 2021 12:13:04 -0400 (EDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1635437584; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=MqVw0Z8vi7JjvCVtjxAexVsSznKzCGLBzzaPnc6KX/k=; b=b5wX3zYsQHqT3a7Utpjtqf1A/oDAn48wO2AGQombk3ibWzgGRQVN8806xz9FTtX0+qNw3R gW4acKO6ckewg799ThxjMuQYbxf7iv/jA4sGgmjBgpdRrQ+D5Sh3qrSUyp0WnelDKLWDkE pci+/ucyR/8tFonM17/pxRe9JnxHITU= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-238-R1OcEdtCNRy5fjOQqmfJWg-1; Thu, 28 Oct 2021 12:13:00 -0400 X-MC-Unique: R1OcEdtCNRy5fjOQqmfJWg-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 594BC112A0A3; Thu, 28 Oct 2021 16:12:14 +0000 (UTC) Received: from starship (unknown [10.40.194.243]) by smtp.corp.redhat.com (Postfix) with ESMTP id BBDF84180; Thu, 28 Oct 2021 16:12:05 +0000 (UTC) Message-ID: Subject: Re: [PATCH v2 35/43] KVM: SVM: Signal AVIC doorbell iff vCPU is in guest mode From: Maxim Levitsky To: Sean Christopherson , Marc Zyngier , Huacai Chen , Aleksandar Markovic , Paul Mackerras , Anup Patel , Paul Walmsley , Palmer Dabbelt , Albert Ou , Christian Borntraeger , Janosch Frank , Paolo Bonzini Date: Thu, 28 Oct 2021 19:12:04 +0300 In-Reply-To: <20211009021236.4122790-36-seanjc@google.com> References: <20211009021236.4122790-1-seanjc@google.com> <20211009021236.4122790-36-seanjc@google.com> User-Agent: Evolution 3.36.5 (3.36.5-2.fc32) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Mailman-Approved-At: Thu, 28 Oct 2021 13:15:59 -0400 Cc: Wanpeng Li , kvm@vger.kernel.org, David Hildenbrand , linux-kernel@vger.kernel.org, Atish Patra , linux-riscv@lists.infradead.org, Claudio Imbrenda , kvmarm@lists.cs.columbia.edu, Joerg Roedel , kvm-ppc@vger.kernel.org, David Matlack , linux-arm-kernel@lists.infradead.org, Jim Mattson , Cornelia Huck , linux-mips@vger.kernel.org, kvm-riscv@lists.infradead.org, Vitaly Kuznetsov X-BeenThere: kvmarm@lists.cs.columbia.edu X-Mailman-Version: 2.1.14 Precedence: list List-Id: Where KVM/ARM decisions are made List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu On Fri, 2021-10-08 at 19:12 -0700, Sean Christopherson wrote: > Signal the AVIC doorbell iff the vCPU is running in the guest. If the vCPU > is not IN_GUEST_MODE, it's guaranteed to pick up any pending IRQs on the > next VMRUN, which unconditionally processes the vIRR. > > Add comments to document the logic. > > Signed-off-by: Sean Christopherson > --- > arch/x86/kvm/svm/avic.c | 14 ++++++++++++-- > 1 file changed, 12 insertions(+), 2 deletions(-) > > diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c > index 208c5c71e827..cbf02e7e20d0 100644 > --- a/arch/x86/kvm/svm/avic.c > +++ b/arch/x86/kvm/svm/avic.c > @@ -674,7 +674,12 @@ int svm_deliver_avic_intr(struct kvm_vcpu *vcpu, int vec) > kvm_lapic_set_irr(vec, vcpu->arch.apic); > smp_mb__after_atomic(); > > - if (avic_vcpu_is_running(vcpu)) { > + /* > + * Signal the doorbell to tell hardware to inject the IRQ if the vCPU > + * is in the guest. If the vCPU is not in the guest, hardware will > + * automatically process AVIC interrupts at VMRUN. > + */ > + if (vcpu->mode == IN_GUEST_MODE) { > int cpu = READ_ONCE(vcpu->cpu); > > /* > @@ -687,8 +692,13 @@ int svm_deliver_avic_intr(struct kvm_vcpu *vcpu, int vec) > if (cpu != get_cpu()) > wrmsrl(SVM_AVIC_DOORBELL, kvm_cpu_get_apicid(cpu)); > put_cpu(); > - } else > + } else { > + /* > + * Wake the vCPU if it was blocking. KVM will then detect the > + * pending IRQ when checking if the vCPU has a wake event. > + */ > kvm_vcpu_wake_up(vcpu); > + } > > return 0; > } It makes sense indeed to avoid ringing the doorbell when the vCPU is not in the guest mode. I do wonder if we want to call kvm_vcpu_wake_up always otherwise, as the vCPU might be just outside of the guest mode and not scheduled out. I don't know how expensive is kvm_vcpu_wake_up in this case. Before this patch, the avic_vcpu_is_running would only be false when the vCPU is scheduled out (e.g when vcpu_put was done on it) Best regards, Maxim Levitsky _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm