Messages in this thread |  | | | Date | Wed, 19 Dec 2007 08:33:39 +0200 | | From | Avi Kivity <> | | Subject | Re: Guest kernel hangs in smp kvm for older kernels prior to tsc sync cleanup |
Ingo Molnar wrote:
>> While the change mentions that it fixes a time warp bug, it also says
>> it should be rare. So clearly kvm smp tsc handing is buggy.
>> Ingo/Thomas, (or anybody else), do you have any insight as to what kvm
>> can be doing wrong to trigger this behavior?
>>
>
> hm. Those time warps were really small, due to the small imperfections
> in the "sync up all CPUs to the same moment and do a WRMSR to clear all
> their TSCs" mechanism. I.e. at most a few usec time warps. I really dont
> know how that should result in udevd hanging. Can you debug udevd in any
> way?
>
>
Adding debug didn't help. I'll try some sysrq keys to see what the
guest thinks is happening.
> so the only thing that KVM might be doing incorrectly here is the
> emulation of the WRMSR that clears the TSC of each vcpu?
>
By inspection, it is correct. Of course I may be missing something, so
I'll write a unit test for it. It should also be much slower than the
native wrmsr.
--
error compiling committee.c: too many arguments to function
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