Re: [Regression, bisected] a3e06bbe8445f57eb949e6474c5a9b30f24d2057:KVM: emulate lapic tsc deadline timer for guest"

[Alexey Zaytsev]

On Wed, Dec 14, 2011 at 11:37, Alexey Zaytsev
<alexey.zaytsev@xxxxxxxxxxx> wrote:
> On Mon, Dec 12, 2011 at 10:13, Liu, Jinsong <jinsong.liu@xxxxxxxxx> 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 Âbetter, 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?
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