Messages in this thread | | | From | "Liu, Jinsong" <> | Date | Tue, 20 Dec 2011 17:26:04 +0800 | Subject | RE: [Regression, bisected] a3e06bbe8445f57eb949e6474c5a9b30f24d2057: KVM: emulate lapic tsc deadline timer for guest" |
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Alexey Zaytsev wrote: > On Tue, Dec 20, 2011 at 10:53, Liu, Jinsong <jinsong.liu@intel.com> > wrote: >> Alexey Zaytsev wrote: >>> On Wed, Dec 14, 2011 at 11:37, Alexey Zaytsev >>> <alexey.zaytsev@nexenta.com> wrote: >>>> On Mon, Dec 12, 2011 at 10:13, Liu, Jinsong <jinsong.liu@intel.com> >>>> wrote: >>>>> Alexey Zaytsev wrote: >>>>>> Hi. >>>>>> >>>>>> After a recent change, qemu --enable-kvm (both 0.15.92 and 1.0) >>>>>> fails to boot illumos. The OS gets stuck pretty late in the boot >>>>>> process, without any hints from the guest. MDB (the illumos >>>>>> kenrnel debugger) failed to clarify the situation at once, the >>>>>> kernel seems to be stuck idling. I've bisected the problem to >>>>>> commit a3e06bbe8445f57eb949e6474c5a9b30f24d2057. Please let me >>>>>> know if you need me to collect any debug information or test any >>>>>> patches. >>>>> >>>>> Alexey, >>>>> >>>>> Does illumos use tsc deadline timer? and do you run it at Intel >>>>> platform? >>>>> >>>>> If yes, would you please help me to collect debug information by >>>>> add some printk points at kvm tsc deadline timer logic? currently >>>>> I totally have no clue to figure out what the issue root from :) >>>>> and, would you please check illumos tsc deadline timer logic by >>>>> confirm whether illumos 1). Enumerate tsc deadline timer >>>>> capability by CPUID; 2). Enable tsc deadline timer mode by lapic >>>>> MMIO; 3). Start tsc deadline timer by WRMSR; >>>> >>>> I think, here's what's going on. We get into >>>> kvm_get_lapic_tscdeadline_msr/kvm_set_lapic_tscdeadline_msr, but >>>> qemu does not use the KVM_CREATE_IRQCHIP ioctl, so we are running >>>> without vcpu->arch.apic and the functions do nothing. And the >>>> Linux guest just handles broken tsc a lot better, so it survives. >>>> Both guests seem to work fine with qemu-kvm, which uses the ioctl. >>>> >>> >>> Hi. Do you need any more info on thins? >> >> Seems illumos works fine w/ qemu-kvm, that's enough. Maybe you need >> to wait qemu-kvm sync into qemu? >> > > Qemu-kvm is fine for me, but this is a regression and should be fixed.
Sorry, I haven't your environment to debug illumos regression. I don't think it directly related to kvm tsc deadline timer, and I think it's no value to do it now, since for linux guest it works fine w/ both qemu & qemu-kvm, for illumos guest you just need wait qemu-kvm sync into qemu.
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