lkml.org 
[lkml]   [2007]   [Dec]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: 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



\
 
 \ /
  Last update: 2007-12-19 07:35    [W:0.068 / U:1.736 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site