On 26/03/21 16:55, Vitaly Kuznetsov wrote:
Another solution is to cast 'hv_clock.system_time' to
's64' in compute_tsc_page_parameters() but it seems we also use
'hv_clock.system_time' in trace_kvm_pvclock_update() as unsigned.
I think that is better. There is no reason really to clamp the value to
to 0, while we know already that tsc_ref->tsc_offset can be either
positive or negative. So treating hv_clock->system_time as signed
before the division would make sense.
It should be just
diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index 58fa8c029867..e573e987f41b 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -1070,9 +1070,7 @@ static bool compute_tsc_page_parameters(struct pvclock_vcpu_time_info *hv_clock,
hv_clock->tsc_to_system_mul,
100);
- tsc_ref->tsc_offset = hv_clock->system_time;
- do_div(tsc_ref->tsc_offset, 100);
- tsc_ref->tsc_offset -=
+ tsc_ref->tsc_offset = div_s64(hv_clock->system_time, 100) -
mul_u64_u64_shr(hv_clock->tsc_timestamp, tsc_ref->tsc_scale, 64);
return true;
}
right? The test passes for me with this change.
Paolo
