Re: [PATCH 0/2] Fix build on i386 due to the latest tsc changes

[Avi Kivity <avi@redhat.com>]

On 02/16/2012 03:48 PM, Avi Kivity wrote:
> The code fixed by the second patch looks suspect though:
>
>   nsdiff = data - kvm->arch.last_tsc_write;
>   nsdiff = (nsdiff * 1000) / vcpu->arch.virtual_tsc_khz;
>
> before the division, nsdiff is in tsc units.  Dividing it by
> tsc_khz/1000 is equivalent to multiplying it by 1000000 and dividing it by
> tsc_hz, so the result is in units of mega-seconds.  I expect we want
>

Actually it results in units of microseconds, while we want nanoseconds.

So maybe the correct code is

  nsdiff = (nsdiff * 1000000) / vcpu->arch.virtual_tsc_khz;

returning nanoseconds.

I note that if the guest writes a large value into the tsc, this breaks.

-- 
error compiling committee.c: too many arguments to function