At 03/15/2012 02:46 AM, Eric Northup Wrote: > On Wed, Mar 14, 2012 at 6:25 AM, Gleb Natapov <gleb@xxxxxxxxxx> 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 -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
