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 X-Spam-Level: X-Spam-Status: No, score=-13.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 520FCC43460 for ; Thu, 22 Apr 2021 09:29:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 192C061422 for ; Thu, 22 Apr 2021 09:29:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235679AbhDVJac (ORCPT ); Thu, 22 Apr 2021 05:30:32 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:47553 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235635AbhDVJab (ORCPT ); Thu, 22 Apr 2021 05:30:31 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1619083796; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=3kZqpcpDryGiJYWT4WCPcehjl0P1U1v7NJiamcT4384=; b=Ll5xGHn+2E+Spixj+yPOqC1o3Z2QgXrUMFFsNvqjh1DfnfPhTHYl6Wluu9MFe8WAhVOGI1 bUZhyO9q7rUTZG0NUNgdmPMsCqZEEXxEItqgksEQ5eDJP1zI4v/UuqXC6D4h3oqMXjP6CO HO+4M6526ahklIt+CuRRqJdh/P/ZqyE= 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-474-nmeL2AHLNr2oNKkFuYW9ew-1; Thu, 22 Apr 2021 05:29:53 -0400 X-MC-Unique: nmeL2AHLNr2oNKkFuYW9ew-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id B6DD5839A42; Thu, 22 Apr 2021 09:29:51 +0000 (UTC) Received: from vitty.brq.redhat.com (unknown [10.40.194.217]) by smtp.corp.redhat.com (Postfix) with ESMTP id 825CC10023AE; Thu, 22 Apr 2021 09:29:49 +0000 (UTC) From: Vitaly Kuznetsov To: kvm@vger.kernel.org, Paolo Bonzini Cc: Sean Christopherson , Wanpeng Li , Jim Mattson , Sebastien Boeuf , linux-kernel@vger.kernel.org Subject: [PATCH] KVM: x86: Properly handle APF vs disabled LAPIC situation Date: Thu, 22 Apr 2021 11:29:48 +0200 Message-Id: <20210422092948.568327-1-vkuznets@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Async PF 'page ready' event may happen when LAPIC is (temporary) disabled. In particular, Sebastien reports that when Linux kernel is directly booted by Cloud Hypervisor, LAPIC is 'software disabled' when APF mechanism is initialized. On initialization KVM tries to inject 'wakeup all' event and puts the corresponding token to the slot. It is, however, failing to inject an interrupt (kvm_apic_set_irq() -> __apic_accept_irq() -> !apic_enabled()) so the guest never gets notified and the whole APF mechanism gets stuck. The same issue is likely to happen if the guest temporary disables LAPIC and a previously unavailable page becomes available. Do two things to resolve the issue: - Avoid dequeuing 'page ready' events from APF queue when LAPIC is disabled. - Trigger an attempt to deliver pending 'page ready' events when LAPIC becomes enabled (SPIV or MSR_IA32_APICBASE). Reported-by: Sebastien Boeuf Signed-off-by: Vitaly Kuznetsov --- arch/x86/kvm/lapic.c | 6 ++++++ arch/x86/kvm/x86.c | 2 +- 2 files changed, 7 insertions(+), 1 deletion(-) diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c index cc369b9ad8f1..49a839d0567a 100644 --- a/arch/x86/kvm/lapic.c +++ b/arch/x86/kvm/lapic.c @@ -296,6 +296,10 @@ static inline void apic_set_spiv(struct kvm_lapic *apic, u32 val) atomic_set_release(&apic->vcpu->kvm->arch.apic_map_dirty, DIRTY); } + + /* Check if there are APF page ready requests pending */ + if (enabled) + kvm_make_request(KVM_REQ_APF_READY, apic->vcpu); } static inline void kvm_apic_set_xapic_id(struct kvm_lapic *apic, u8 id) @@ -2261,6 +2265,8 @@ void kvm_lapic_set_base(struct kvm_vcpu *vcpu, u64 value) if (value & MSR_IA32_APICBASE_ENABLE) { kvm_apic_set_xapic_id(apic, vcpu->vcpu_id); static_branch_slow_dec_deferred(&apic_hw_disabled); + /* Check if there are APF page ready requests pending */ + kvm_make_request(KVM_REQ_APF_READY, vcpu); } else { static_branch_inc(&apic_hw_disabled.key); atomic_set_release(&apic->vcpu->kvm->arch.apic_map_dirty, DIRTY); diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index a06a6f48386d..001c6a445eaf 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -11296,7 +11296,7 @@ bool kvm_arch_can_dequeue_async_page_present(struct kvm_vcpu *vcpu) if (!kvm_pv_async_pf_enabled(vcpu)) return true; else - return apf_pageready_slot_free(vcpu); + return kvm_lapic_enabled(vcpu) && apf_pageready_slot_free(vcpu); } void kvm_arch_start_assignment(struct kvm *kvm) -- 2.30.2