From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:60639) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1S84fQ-0000Y4-1S for qemu-devel@nongnu.org; Thu, 15 Mar 2012 03:00:09 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1S84fJ-0008Ax-Mn for qemu-devel@nongnu.org; Thu, 15 Mar 2012 03:00:07 -0400 Received: from [222.73.24.84] (port=47144 helo=song.cn.fujitsu.com) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1S84fJ-00089r-B8 for qemu-devel@nongnu.org; Thu, 15 Mar 2012 03:00:01 -0400 Message-ID: <4F6193D8.8050101@cn.fujitsu.com> Date: Thu, 15 Mar 2012 15:01:44 +0800 From: Wen Congyang MIME-Version: 1.0 References: <4F606A7C.9090900@cn.fujitsu.com> <4F606DCC.3020908@redhat.com> <4F60726E.3090807@cn.fujitsu.com> <4F607325.6050607@redhat.com> <20120314104608.GU2304@redhat.com> <4F607789.4010109@redhat.com> <4F607CE4.2060809@cn.fujitsu.com> <4F609822.7050502@redhat.com> <20120314131415.GB2304@redhat.com> <4F609A15.5020902@redhat.com> <20120314132552.GC2304@redhat.com> In-Reply-To: Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=ISO-8859-1 Subject: Re: [Qemu-devel] [PATCH 0/2 v3] kvm: notify host when guest panicked List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Eric Northup Cc: kvm list , Gleb Natapov , Jan Kiszka , qemu-devel , "linux-kernel@vger.kernel.org" , Avi Kivity , Amit Shah , KAMEZAWA Hiroyuki At 03/15/2012 02:46 AM, Eric Northup Wrote: > On Wed, Mar 14, 2012 at 6:25 AM, Gleb Natapov wrote: > >> On Wed, Mar 14, 2012 at 03:16:05PM +0200, Avi Kivity wrote: >>> On 03/14/2012 03:14 PM, Gleb Natapov wrote: >>>> On Wed, Mar 14, 2012 at 03:07:46PM +0200, Avi Kivity wrote: >>>>> On 03/14/2012 01:11 PM, Wen Congyang wrote: >>>>>>> >>>>>>> I don't think we want to use the driver. Instead, have a small >> piece of >>>>>>> code that resets the device and pushes out a string (the panic >> message?) >>>>>>> without any interrupts etc. >>>>>>> >>>>>>> It's still going to be less reliable than a hypercall, I agree. >>>>>> >>>>>> Do you still want to use complicated and less reliable way? >>>>> >>>>> Are you willing to try it out and see how complicated it really is? >>>>> >>>>> While it's more complicated, it's also more flexible. You can >>>>> communicate the panic message, whether the guest is attempting a >> kdump >>>>> and its own recovery or whether it wants the host to do it, etc., you >>>>> can communicate less severe failures like oopses. >>>>> >>>> hypercall can take arguments to achieve the same. >>> >>> It has to be designed in advance; and every time we notice something's >>> missing we have to update the host kernel. >>> >> >> We and in the designed stage now. Not to late to design something flexible >> :) Panic hypercall can take GPA of a buffer where host puts panic info >> as a parameter. This buffer can be read by QEMU and passed to management. >> > > If a host kernel change is in the works, I think it might be cleanest to > have the host kernel export a new kind of VCPU exit for unhandled-by-KVM > hypercalls. Then usermode can respond to the hypercall as appropriate. > This would permit adding or changing future hypercalls without host kernel > changes. > > "Guest panic" is almost the definition of not-a-fast-path, and so what's > the reason to handle it in the host kernel. > > Punting to user-space wouldn't be a magic bullet for getting good > interfaces designed, but in my opinion it is a better place to be doing > them. > Do you mean that: the guest execute vmcall instruction, and the host kernel exits to userspace. The userspace will deal with the vmexit? Thanks Wen Congyang