On Thu, 28 Feb 2019, Dongli Zhang wrote:
The root cause is that the return type of jiffies_to_usecs() is 'unsigned int', but not 'unsigned long'. As a result, the leading 32 bits are discarded.
Errm. No. The root cause is that jiffies_to_usecs() is used for that in the first place. The function has been that way forever and all usage sites (except a broken dev_debug print in infiniband) feed delta values. Yes, it could have documentation....
jiffies_to_usecs() is indirectly triggered by cputime_to_nsecs() at line 264. If guest is already up for long time, the initial steal time for new vcpu might be large and the leading 32 bits of jiffies_to_usecs() would be discarded.
So far, I have two solutions:
- Change the return type from 'unsigned int' to 'unsigned long' as in above
link and I am afraid it would bring side effect. The return type in latest mainline kernel is still 'unsigned int'.
Changing it to unsigned long would just solve the issue for 64bit.
Thanks,
tglx