Gleb Natapov wrote: > On Wed, Dec 02, 2009 at 01:25:39PM +0100, Jan Kiszka wrote: >> Gleb Natapov wrote: >>> On Wed, Dec 02, 2009 at 01:04:16PM +0100, Jan Kiszka wrote: >>>> Gleb Natapov wrote: >>>>> On Tue, Dec 01, 2009 at 10:51:26AM -0200, Glauber Costa wrote: >>>>>> This is a repost of the -smp series. Note that it depends on >>>>>> irqchip-in-kernel, >>>>>> that is already in staging. Also, you'll have to enable the io-thread, >>>>>> for the time >>>>>> being. >>>>>> >>>>>> >From the last version, main change is that I am not calling queue_work >>>>>> >automatically >>>>>> from vcpu ioctls. queue_work is only used currently for the gdb stub. >>>>>> >>>>>> All other uses were by-passed by the new qemu_register_vcpu_reset(), >>>>>> since most >>>>>> of it uses (all racy) came from the reset handlers. >>>>>> >>>>> Looks good to me except one thing. I don't see how you are addressing >>>>> the problem fixed by commit b8a7857071b477b28d3055e33ff0298fc91f329a >>>>> in qemu-kvm. The problem is that mp_state can change in kernel between >>>>> call to kvm_cpu_synchronize_state() and vcpu re-entry. In this case old >>>>> mp_state will overwrite new one. >>>> + nmi_pending >>>> + sipi_vector >>>> >>>> These things need to be fixed at kernel level as discussed recently: >>>> Asynchronous changes done by in-kernel subsystems need to be queued and >>>> replayed with a higher priority than user space changes. User space need >>>> to stop the vm if it does not want to be overruled. >>>> >>> Long term yes. Short term qemu need to work with existing kernels. >> Avi's answer was different [1]. >> >> Jan >> >> [1] http://permalink.gmane.org/gmane.comp.emulators.kvm.devel/43288 >> > I don't think we can realistically fix all older kernels. Anyway if the > workaround for the bug will not be done in qemu we need to fix it in kernel > ASAP and start to propagate it to stable releases. >
Upstream could still easily deny in-kernel irqchip support if the host kvm is not recent enough. qemu-kvm currently has a different policy /wrt old kvm modules, so we may work around the mp_state and vcpu_events issues there (just cleaner than so far). Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux
