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=-19.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT 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 3C393C2D0D7 for ; Wed, 12 May 2021 18:06:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0F16E61166 for ; Wed, 12 May 2021 18:06:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1353164AbhELSHI (ORCPT ); Wed, 12 May 2021 14:07:08 -0400 Received: from mail.kernel.org ([198.145.29.99]:40468 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241626AbhELQ1j (ORCPT ); Wed, 12 May 2021 12:27:39 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id CD27F61DF7; Wed, 12 May 2021 15:54:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1620834870; bh=xAU5NaZrKs84wEQ0MftKqBtsgv0dD5UnYI5EjBqH2Z8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=08ZAhJMWvSau5pCTvyGsnGwcGXWCDJ1X5H0OA+NUiZAuI6HH+BiiARYYKVn1GAwRY Wni2H03xqp9jL2vSwugM3dcgRqE/0OdvhrTQtWNtt0klHDnzPVp5A9VKo/DwQXVBgD A5vGlvCrpnE6rCFNEIGjfbOJcx5fanqG2OjISAHY= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Sebastien Boeuf , Vitaly Kuznetsov , Paolo Bonzini Subject: [PATCH 5.12 109/677] KVM: x86: Properly handle APF vs disabled LAPIC situation Date: Wed, 12 May 2021 16:42:35 +0200 Message-Id: <20210512144840.841629030@linuxfoundation.org> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210512144837.204217980@linuxfoundation.org> References: <20210512144837.204217980@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Vitaly Kuznetsov commit 2f15d027c05fac406decdb5eceb9ec0902b68f53 upstream. 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 Message-Id: <20210422092948.568327-1-vkuznets@redhat.com> Cc: stable@vger.kernel.org Signed-off-by: Paolo Bonzini Signed-off-by: Greg Kroah-Hartman --- arch/x86/kvm/lapic.c | 6 ++++++ arch/x86/kvm/x86.c | 2 +- 2 files changed, 7 insertions(+), 1 deletion(-) --- a/arch/x86/kvm/lapic.c +++ b/arch/x86/kvm/lapic.c @@ -296,6 +296,10 @@ static inline void apic_set_spiv(struct 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 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); --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -11293,7 +11293,7 @@ bool kvm_arch_can_dequeue_async_page_pre 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)