From nobody Wed Nov 5 14:24:49 2025 Delivered-To: importer@patchew.org Received-SPF: pass (zoho.com: domain of gnu.org designates 208.118.235.17 as permitted sender) client-ip=208.118.235.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Authentication-Results: mx.zohomail.com; spf=pass (zoho.com: domain of gnu.org designates 208.118.235.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=fail(p=none dis=none) header.from=redhat.com Return-Path: Received: from lists.gnu.org (lists.gnu.org [208.118.235.17]) by mx.zohomail.com with SMTPS id 153536816645451.661447531749104; Mon, 27 Aug 2018 04:09:26 -0700 (PDT) Received: from localhost ([::1]:52486 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fuFOe-00020G-W9 for importer@patchew.org; Mon, 27 Aug 2018 07:09:25 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:37183) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fuFMh-00011D-QA for qemu-devel@nongnu.org; Mon, 27 Aug 2018 07:07:24 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fuFMc-0006ge-Vf for qemu-devel@nongnu.org; Mon, 27 Aug 2018 07:07:23 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:59226 helo=mx1.redhat.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1fuFMc-0006fM-Qb for qemu-devel@nongnu.org; Mon, 27 Aug 2018 07:07:18 -0400 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.rdu2.redhat.com [10.11.54.6]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id BCE0840201BE; Mon, 27 Aug 2018 11:07:17 +0000 (UTC) Received: from dell-r430-03.lab.eng.brq.redhat.com (dell-r430-03.lab.eng.brq.redhat.com [10.37.153.18]) by smtp.corp.redhat.com (Postfix) with ESMTP id A8F0A2166B41; Mon, 27 Aug 2018 11:07:12 +0000 (UTC) From: Igor Mammedov To: qemu-devel@nongnu.org Date: Mon, 27 Aug 2018 13:07:10 +0200 Message-Id: <1535368030-214556-1-git-send-email-imammedo@redhat.com> X-Scanned-By: MIMEDefang 2.78 on 10.11.54.6 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.6]); Mon, 27 Aug 2018 11:07:17 +0000 (UTC) X-Greylist: inspected by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.6]); Mon, 27 Aug 2018 11:07:17 +0000 (UTC) for IP:'10.11.54.6' DOMAIN:'int-mx06.intmail.prod.int.rdu2.redhat.com' HELO:'smtp.corp.redhat.com' FROM:'imammedo@redhat.com' RCPT:'' X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 66.187.233.73 Subject: [Qemu-devel] [PATCH] pc: make sure that guest isn't able to unplug the first cpu X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: david@redhat.com, cohuck@redhat.com, groug@kaod.org, mst@redhat.com, pbonzini@redhat.com, david@gibson.dropbear.id.au Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail: RDMRC_1 RSF_0 Z_629925259 SPT_0 Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" The first cpu unplug wasn't ever supported and corresponding monitor/qmp commands refuse to unplug it. However guest is able to issue eject request either using following command: # echo 1 >/sys/devices/system/cpu/cpu0/firmware_node/eject or directly writing to cpu hotplug registers, which makes qemu crash with SIGSEGV following back trace: kvm_flush_coalesced_mmio_buffer () while (ring->first !=3D ring->last) ... qemu_flush_coalesced_mmio_buffer prepare_mmio_access flatview_read_continue flatview_read address_space_read_full address_space_rw kvm_cpu_exec(cpu!0) qemu_kvm_cpu_thread_fn the reason for which is that ring =3D=3D KVMState::coalesced_mmio_ring happens to be a part of 1st CPU that was uplugged by guest. Fix it by forbidding 1st cpu unplug from guest side and in addition remove CPU0._EJ0 ACPI method to make clear that unplug of the first CPU is not supported. Signed-off-by: Igor Mammedov --- CCing spapr and s390x folks in case targets need to prevent 1st CPU unplug = as well CC: mst@redhat.com CC: pbonzini@redhat.com CC: david@gibson.dropbear.id.au CC: groug@kaod.org CC: david@redhat.com CC: cohuck@redhat.com --- hw/acpi/cpu.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/hw/acpi/cpu.c b/hw/acpi/cpu.c index 5ae595e..4bb8371 100644 --- a/hw/acpi/cpu.c +++ b/hw/acpi/cpu.c @@ -117,7 +117,7 @@ static void cpu_hotplug_wr(void *opaque, hwaddr addr, u= int64_t data, DeviceState *dev =3D NULL; HotplugHandler *hotplug_ctrl =3D NULL; =20 - if (!cdev->cpu) { + if (!cdev->cpu || cdev->cpu =3D=3D first_cpu) { trace_cpuhp_acpi_ejecting_invalid_cpu(cpu_st->selector); break; } @@ -541,9 +541,11 @@ void build_cpus_aml(Aml *table, MachineState *machine,= CPUHotplugFeatures opts, aml_buffer(madt_buf->len, (uint8_t *)madt_buf->data))); g_array_free(madt_buf, true); =20 - method =3D aml_method("_EJ0", 1, AML_NOTSERIALIZED); - aml_append(method, aml_call1(CPU_EJECT_METHOD, uid)); - aml_append(dev, method); + if (CPU(arch_ids->cpus[i].cpu) !=3D first_cpu) { + method =3D aml_method("_EJ0", 1, AML_NOTSERIALIZED); + aml_append(method, aml_call1(CPU_EJECT_METHOD, uid)); + aml_append(dev, method); + } =20 method =3D aml_method("_OST", 3, AML_SERIALIZED); aml_append(method, --=20 2.7.4