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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 673DBC433EF for ; Thu, 10 Mar 2022 09:17:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240690AbiCJJSy (ORCPT ); Thu, 10 Mar 2022 04:18:54 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33916 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240688AbiCJJSu (ORCPT ); Thu, 10 Mar 2022 04:18:50 -0500 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 3BEA0133958 for ; Thu, 10 Mar 2022 01:17:48 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1646903867; h=from:from:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:in-reply-to:in-reply-to: references:references; bh=K1oHDE2zEJ3OzOLvIxaERL60v91ZzjYYqlVixsRYN5Q=; b=XfQ3V7RA5vrRhAHkVgHnS6biJQvmpRvk6YKTsRxUSJhZjRU1frKD32AJp1ChToGCtNgyBW vBH87xd7X+1bQXMgDa6eKsokDEkkCKtD2gV5VsWdIR5UFGCf7BcvfqVL65vrPZNKma5FtR QoY4sGWB7SGsnT9TFKlDQZUpM8teY8U= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-571-mlJUzm46PZekj6cxtm8mIA-1; Thu, 10 Mar 2022 04:17:44 -0500 X-MC-Unique: mlJUzm46PZekj6cxtm8mIA-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 8605B801AB2; Thu, 10 Mar 2022 09:17:43 +0000 (UTC) Received: from redhat.com (unknown [10.33.36.68]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 39B6A7FCF2; Thu, 10 Mar 2022 09:17:21 +0000 (UTC) Date: Thu, 10 Mar 2022 09:17:19 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Chenyi Qiang Cc: Paolo Bonzini , Richard Henderson , Eduardo Habkost , Marcelo Tosatti , Xiaoyao Li , kvm@vger.kernel.org, qemu-devel@nongnu.org Subject: Re: [PATCH 2/2] i386: Add notify VM exit support Message-ID: Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= References: <20220310090205.10645-1-chenyi.qiang@intel.com> <20220310090205.10645-3-chenyi.qiang@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20220310090205.10645-3-chenyi.qiang@intel.com> User-Agent: Mutt/2.1.5 (2021-12-30) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Thu, Mar 10, 2022 at 05:02:05PM +0800, Chenyi Qiang wrote: > There are cases that malicious virtual machine can cause CPU stuck (due > to event windows don't open up), e.g., infinite loop in microcode when > nested #AC (CVE-2015-5307). No event window means no event (NMI, SMI and > IRQ) can be delivered. It leads the CPU to be unavailable to host or > other VMs. Notify VM exit is introduced to mitigate such kind of > attacks, which will generate a VM exit if no event window occurs in VM > non-root mode for a specified amount of time (notify window). > > A new KVM capability KVM_CAP_X86_NOTIFY_VMEXIT is exposed to user space > so that the user can query the capability and set the expected notify > window when creating VMs. > > If notify VM exit happens with VM_INVALID_CONTEXT, hypervisor should > exit to user space with the exit reason KVM_EXIT_NOTIFY to inform the > fatal case. Then user space can inject a SHUTDOWN event to the target > vcpu. This is implemented by defining a new bit in flags field of > kvm_vcpu_event in KVM_SET_VCPU_EVENTS ioctl. > > Signed-off-by: Chenyi Qiang > --- > hw/i386/x86.c | 24 ++++++++++++++++++ > include/hw/i386/x86.h | 3 +++ > target/i386/kvm/kvm.c | 58 ++++++++++++++++++++++++++++--------------- > 3 files changed, 65 insertions(+), 20 deletions(-) > > diff --git a/hw/i386/x86.c b/hw/i386/x86.c > index b84840a1bb..25e6c50b1e 100644 > --- a/hw/i386/x86.c > +++ b/hw/i386/x86.c > @@ -1309,6 +1309,23 @@ static void machine_set_sgx_epc(Object *obj, Visitor *v, const char *name, > qapi_free_SgxEPCList(list); > } > > +static void x86_machine_get_notify_window(Object *obj, Visitor *v, > + const char *name, void *opaque, Error **errp) > +{ > + X86MachineState *x86ms = X86_MACHINE(obj); > + int32_t notify_window = x86ms->notify_window; > + > + visit_type_int32(v, name, ¬ify_window, errp); > +} > + > +static void x86_machine_set_notify_window(Object *obj, Visitor *v, > + const char *name, void *opaque, Error **errp) > +{ > + X86MachineState *x86ms = X86_MACHINE(obj); > + > + visit_type_int32(v, name, &x86ms->notify_window, errp); > +} > + > static void x86_machine_initfn(Object *obj) > { > X86MachineState *x86ms = X86_MACHINE(obj); > @@ -1319,6 +1336,7 @@ static void x86_machine_initfn(Object *obj) > x86ms->oem_id = g_strndup(ACPI_BUILD_APPNAME6, 6); > x86ms->oem_table_id = g_strndup(ACPI_BUILD_APPNAME8, 8); > x86ms->bus_lock_ratelimit = 0; > + x86ms->notify_window = -1; > } IIUC from the kernel patch, this negative value leaves the protection disabled, and thus the host remains vulnerable to the CVE. I would expect this ought to set a suitable default value to fix the flaw. Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|