From mboxrd@z Thu Jan  1 00:00:00 1970
From: Marcelo Tosatti <mtosatti@redhat.com>
Subject: Re: [PATCH v2 4/4] KVM: x86: Add VCPU substate for NMI states
Date: Mon, 19 Oct 2009 18:32:54 -0200
Message-ID: <20091019203254.GD17781@amt.cnet>
References: <20091015170535.5076.91206.stgit@mchn012c.ww002.siemens.net> <20091015170536.5076.56790.stgit@mchn012c.ww002.siemens.net>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Cc: Avi Kivity <avi@redhat.com>, kvm@vger.kernel.org
To: Jan Kiszka <jan.kiszka@siemens.com>
Return-path: <kvm-owner@vger.kernel.org>
Received: from mx1.redhat.com ([209.132.183.28]:23116 "EHLO mx1.redhat.com"
	rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
	id S1753274AbZJSUc6 (ORCPT <rfc822;kvm@vger.kernel.org>);
	Mon, 19 Oct 2009 16:32:58 -0400
Content-Disposition: inline
In-Reply-To: <20091015170536.5076.56790.stgit@mchn012c.ww002.siemens.net>
Sender: kvm-owner@vger.kernel.org
List-ID: <kvm.vger.kernel.org>

On Thu, Oct 15, 2009 at 07:05:36PM +0200, Jan Kiszka wrote:
> This plugs an NMI-related hole in the VCPU synchronization between
> kernel and user space. So far, neither pending NMIs nor the inhibit NMI
> mask was properly read/set which was able to cause problems on
> vmsave/restore, live migration and system reset. Fix it by making use
> of the new VCPU substate interface.
> 
> Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
> ---
> 
>  Documentation/kvm/api.txt       |   12 ++++++++++++
>  arch/x86/include/asm/kvm.h      |    7 +++++++
>  arch/x86/include/asm/kvm_host.h |    2 ++
>  arch/x86/kvm/svm.c              |   22 ++++++++++++++++++++++
>  arch/x86/kvm/vmx.c              |   30 ++++++++++++++++++++++++++++++
>  arch/x86/kvm/x86.c              |   26 ++++++++++++++++++++++++++
>  6 files changed, 99 insertions(+), 0 deletions(-)
> 
> diff --git a/Documentation/kvm/api.txt b/Documentation/kvm/api.txt
> index bee5bbd..e483edb 100644
> --- a/Documentation/kvm/api.txt
> +++ b/Documentation/kvm/api.txt
> @@ -848,3 +848,15 @@ Deprecates: KVM_GET/SET_CPUID2
>  Architectures: x86
>  Payload: struct kvm_lapic
>  Deprecates: KVM_GET/SET_LAPIC
> +
> +6.8 KVM_X86_VCPU_STATE_NMI
> +
> +Architectures: x86
> +Payload: struct kvm_nmi_state
> +Deprecates: -
> +
> +struct kvm_nmi_state {
> +       __u8 pending;
> +       __u8 masked;
> +       __u8 pad1[6];

Don't you also have to save "nmi_injected", in case of failure during
NMI delivery.

BTW, what happens to exceptions that fail to be delivered? Can't see
where they are saved/restored across migration.