On 02/20/2018 04:41 PM, David Hildenbrand wrote: > On 20.02.2018 16:36, Christian Borntraeger wrote: >> >> >> On 02/07/2018 12:46 PM, David Hildenbrand wrote: >>> For now, we don't take care of over/underflows. Especially underflows >>> are critical: >>> >>> Assume the epoch is currently 0 and we get a sync request for delta=1, >>> meaning the TOD is moved forward by 1 and we have to fix it up by >>> subtracting 1 from the epoch. Right now, this will leave the epoch >>> index untouched, resulting in epoch=-1, epoch_idx=0, which is wrong. >>> >>> We have to take care of over and underflows, also for the VSIE case. So >>> let's factor out calculation into a separate function. >>> >>> Signed-off-by: David Hildenbrand <david@xxxxxxxxxx> >>> --- >>> arch/s390/kvm/kvm-s390.c | 32 +++++++++++++++++++++++++++++--- >>> 1 file changed, 29 insertions(+), 3 deletions(-) >>> >>> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c >>> index d007b737cd4d..c2b62379049e 100644 >>> --- a/arch/s390/kvm/kvm-s390.c >>> +++ b/arch/s390/kvm/kvm-s390.c >>> @@ -179,6 +179,28 @@ int kvm_arch_hardware_enable(void) >>> static void kvm_gmap_notifier(struct gmap *gmap, unsigned long start, >>> unsigned long end); >>> >>> +static void kvm_clock_sync_scb(struct kvm_s390_sie_block *scb, u64 delta) >>> +{ >>> + u64 delta_idx = 0; >> >> we only add it to epdx, so should it be u8? > > Indeed, this should be u8. > >>> + >>> + /* >>> + * The TOD jumps by delta, we have to compensate this by adding >>> + * -delta to the epoch. >>> + */ >>> + delta = -delta; >>> + >>> + /* sign-extension - we're adding to signed values below */ >>> + if ((s64)delta < 0) >>> + delta_idx = 0xff; >> >> and -1 then here? > > Yes, thanks! with that Reviewed-by: Christian Borntraeger <borntraeger@xxxxxxxxxx> applied and changed to u8. In plan to submit patch 1,3 and 4 for 4.16 -- To unsubscribe from this list: send the line "unsubscribe linux-s390" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html