From mboxrd@z Thu Jan  1 00:00:00 1970
From: Sasha Levin <levinsasha928@gmail.com>
Subject: Re: [PATCH 2/2] kvm tools: inject MSI directly without going through
 a GSI
Date: Sun, 05 Aug 2012 11:14:19 +0200
Message-ID: <501E396B.3060700@gmail.com>
References: <1343917764-28715-1-git-send-email-levinsasha928@gmail.com> <1343917764-28715-2-git-send-email-levinsasha928@gmail.com> <CAOJsxLFOUjoezkVrvijjWmpBUCyYBh1GrZ2TJQSnRUgredbJ8g@mail.gmail.com> <501CEBAB.1040504@gmail.com> <CAOJsxLFRiT1O_r-DZ-r9zucy5VMu=TBnU0=_KP9f_tPVHFXWTQ@mail.gmail.com> <501E1A90.1040303@gmail.com> <CAOJsxLFY8+Ug2uijyp+4vdSJeUsfRKbiUjgfowKo9sFBb-KO3w@mail.gmail.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 7bit
Cc: mingo@elte.hu, gorcunov@gmail.com, kvm@vger.kernel.org
To: Pekka Enberg <penberg@kernel.org>
Return-path: <kvm-owner@vger.kernel.org>
Received: from mail-ob0-f174.google.com ([209.85.214.174]:34225 "EHLO
	mail-ob0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1752483Ab2HEJNo (ORCPT <rfc822;kvm@vger.kernel.org>);
	Sun, 5 Aug 2012 05:13:44 -0400
Received: by obbuo13 with SMTP id uo13so3985488obb.19
        for <kvm@vger.kernel.org>; Sun, 05 Aug 2012 02:13:43 -0700 (PDT)
In-Reply-To: <CAOJsxLFY8+Ug2uijyp+4vdSJeUsfRKbiUjgfowKo9sFBb-KO3w@mail.gmail.com>
Sender: kvm-owner@vger.kernel.org
List-ID: <kvm.vger.kernel.org>

On 08/05/2012 11:08 AM, Pekka Enberg wrote:
> On 08/04/2012 01:02 PM, Pekka Enberg wrote:
>>> No, it's not running 3.5. We need to support older *host* kernels,
>>> though.
> 
> On Sun, Aug 5, 2012 at 10:02 AM, Sasha Levin <levinsasha928@gmail.com> wrote:
>> Do we? Don't we need to support just the kernel that the tool was
>> built with?
> 
> We only do that for *guest kernels* if we have to but we've always been
> compatible with older host kernels.
> 
> Isn't there a capability flag that KVM sets if KVM_SIGNAL_MSI is
> supported? Just store that in 'struct kvm" and switch between
> virtio_pci__signal_msi() and kvm__irq_trigger() depending on wheter the
> flag is set.

There is, but we've broken backwards compatibility for guests several times before as well - which is why I assumed thats fine.