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=-11.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham 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 B9569C2B9F4 for ; Mon, 14 Jun 2021 18:21:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9154A613B3 for ; Mon, 14 Jun 2021 18:21:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234002AbhFNSXx (ORCPT ); Mon, 14 Jun 2021 14:23:53 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:59780 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233222AbhFNSXw (ORCPT ); Mon, 14 Jun 2021 14:23:52 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1623694909; 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=1Bj73rQz0vJpO/BmXX/AlVN+5Q+2iRN43S+kdMpQ3Qs=; b=ZUwV3wRtakTSqNcLS6xTE0qjT81orJMbhzQC6nLVXtg1y1SPbwLPNOv02IcyNnSl43VQks mBkQOKwwqkdSPI7RWgMN/3KLPXuB0m8sFpIrOBuYn2DCNmfJ0MOY2wKqT56aa9T4Kq/lX9 SiZ0H8L2hTzr/Q9wIoqrULzvC35ru3I= 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-172-3RWwR3x-OM-eOVtu_V-MhA-1; Mon, 14 Jun 2021 14:21:47 -0400 X-MC-Unique: 3RWwR3x-OM-eOVtu_V-MhA-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 54503801B1D; Mon, 14 Jun 2021 18:21:46 +0000 (UTC) Received: from starship (unknown [10.40.194.6]) by smtp.corp.redhat.com (Postfix) with ESMTP id 34EA65D6A8; Mon, 14 Jun 2021 18:21:42 +0000 (UTC) Message-ID: <2de388ee85e6dc771fa823cd34ccf21adfec1e6a.camel@redhat.com> Subject: Re: [PATCH v3 0/4] KVM: x86: hyper-v: Conditionally allow SynIC with APICv/AVIC From: Maxim Levitsky To: Paolo Bonzini , Vitaly Kuznetsov Cc: Sean Christopherson , Wanpeng Li , Jim Mattson , linux-kernel@vger.kernel.org, kvm@vger.kernel.org Date: Mon, 14 Jun 2021 21:21:42 +0300 In-Reply-To: <2f59a441-279c-d257-52ab-cdd3f2ee5704@redhat.com> References: <20210609150911.1471882-1-vkuznets@redhat.com> <87zgvsx5b1.fsf@vitty.brq.redhat.com> <2f59a441-279c-d257-52ab-cdd3f2ee5704@redhat.com> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.36.5 (3.36.5-2.fc32) MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Mon, 2021-06-14 at 15:08 +0200, Paolo Bonzini wrote: > On 14/06/21 11:51, Maxim Levitsky wrote: > > On Mon, 2021-06-14 at 09:40 +0200, Vitaly Kuznetsov wrote: > > > Maxim Levitsky writes: > > > > > > > On Wed, 2021-06-09 at 17:09 +0200, Vitaly Kuznetsov wrote: > > > > > Changes since v2: > > > > > - First two patches got merged, rebase. > > > > > - Use 'enable_apicv = avic = ...' in PATCH1 [Paolo] > > > > > - Collect R-b tags for PATCH2 [Sean, Max] > > > > > - Use hv_apicv_update_work() to get out of SRCU lock [Max] > > > > > - "KVM: x86: Check for pending interrupts when APICv is getting disabled" > > > > > added. > > > > > > > > > > Original description: > > > > > > > > > > APICV_INHIBIT_REASON_HYPERV is currently unconditionally forced upon > > > > > SynIC activation as SynIC's AutoEOI is incompatible with APICv/AVIC. It is, > > > > > however, possible to track whether the feature was actually used by the > > > > > guest and only inhibit APICv/AVIC when needed. > > > > > > > > > > The series can be tested with the followin hack: > > > > > > > > > > diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c > > > > > index 9a48f138832d..65a9974f80d9 100644 > > > > > --- a/arch/x86/kvm/cpuid.c > > > > > +++ b/arch/x86/kvm/cpuid.c > > > > > @@ -147,6 +147,13 @@ void kvm_update_cpuid_runtime(struct kvm_vcpu *vcpu) > > > > > vcpu->arch.ia32_misc_enable_msr & > > > > > MSR_IA32_MISC_ENABLE_MWAIT); > > > > > } > > > > > + > > > > > + /* Dirty hack: force HV_DEPRECATING_AEOI_RECOMMENDED. Not to be merged! */ > > > > > + best = kvm_find_cpuid_entry(vcpu, HYPERV_CPUID_ENLIGHTMENT_INFO, 0); > > > > > + if (best) { > > > > > + best->eax &= ~HV_X64_APIC_ACCESS_RECOMMENDED; > > > > > + best->eax |= HV_DEPRECATING_AEOI_RECOMMENDED; > > > > > + } > > > > > } > > > > > EXPORT_SYMBOL_GPL(kvm_update_cpuid_runtime); > > > > > > > > > > Vitaly Kuznetsov (4): > > > > > KVM: x86: Use common 'enable_apicv' variable for both APICv and AVIC > > > > > KVM: x86: Drop vendor specific functions for APICv/AVIC enablement > > > > > KVM: x86: Check for pending interrupts when APICv is getting disabled > > > > > KVM: x86: hyper-v: Deactivate APICv only when AutoEOI feature is in > > > > > use > > > > > > > > > > arch/x86/include/asm/kvm_host.h | 9 +++++- > > > > > arch/x86/kvm/hyperv.c | 51 +++++++++++++++++++++++++++++---- > > > > > arch/x86/kvm/svm/avic.c | 14 ++++----- > > > > > arch/x86/kvm/svm/svm.c | 22 ++++++++------ > > > > > arch/x86/kvm/svm/svm.h | 2 -- > > > > > arch/x86/kvm/vmx/capabilities.h | 1 - > > > > > arch/x86/kvm/vmx/vmx.c | 2 -- > > > > > arch/x86/kvm/x86.c | 18 ++++++++++-- > > > > > 8 files changed, 86 insertions(+), 33 deletions(-) > > > > > > > > > > > > > Hi! > > > > > > > > I hate to say it, but at least one of my VMs doesn't boot amymore > > > > with avic=1, after the recent updates. I'll bisect this soon, > > > > but this is likely related to this series. > > > > > > > > I will also review this series very soon. > > > > > > > > When the VM fails, it hangs on the OVMF screen and I see this > > > > in qemu logs: > > > > > > > > KVM: injection failed, MSI lost (Operation not permitted) > > > > KVM: injection failed, MSI lost (Operation not permitted) > > > > KVM: injection failed, MSI lost (Operation not permitted) > > > > KVM: injection failed, MSI lost (Operation not permitted) > > > > KVM: injection failed, MSI lost (Operation not permitted) > > > > KVM: injection failed, MSI lost (Operation not permitted) > > > > > > > > > > -EPERM?? Interesting... strace(1) may come handy... > > > > Hi Vitaly! > > > > I spent all yesterday debugging this and I found out what is going on: > > (spoiler alert: hacks are bad) > > > > The call to kvm_request_apicv_update was moved to a delayed work which is fine at first glance > > but turns out that we both don't notice that kvm doesn't allow to update the guest > > memory map from non vcpu thread which is what kvm_request_apicv_update does > > on AVIC. > > > > The memslot update is to switch between regular r/w mapped dummy page > > which is not really used but doesn't hurt to be there, and between paging entry with > > reserved bits, used for MMIO, which AVIC sadly needs because it is written in the > > spec that AVIC's MMIO despite being redirected to the avic_vapic_bar, still needs a valid > > R/W mapping in the NPT, whose physical address is ignored. > > > > So, in avic_update_access_page we have this nice hack: > > > > if ((kvm->arch.apic_access_page_done == activate) || > > (kvm->mm != current->mm)) > > goto out; > > > > So instead of crashing this function just does nothing. > > So AVIC MMIO is still mapped R/W to a dummy page, but the AVIC itself > > is disabled on all vCPUs by kvm_request_apicv_update (with > > KVM_REQ_APICV_UPDATE request) > > > > So now all guest APIC writes just disappear to that dummy > > page, and we have a guest that seems to run but can't really > > continue. > > > > The -EPERM in the error message I reported, is just -1, returned by > > KVM_SIGNAL_MSI which is likely result of gross missmatch between > > state of the KVM's APIC registers and that dummy page which contains > > whatever the guest wrote there and what the guest thinks > > the APIC registers are. > > > > I am curently thinking on how to do the whole thing with > > KVM's requests, I'll try to prepare a patch today. > > I'll drop the last two patches in the series. Actually only the patch 4 is problemetic, and patch 3 IMHO does fix an issue. Best regards, Maxim Levitsky > > Paolo >