Adding Collin.
On 02/05/2018 11:40 AM, David Hildenbrand wrote:
> Missed when enabling the Multiple-epoch facility. If the facility is
> installed and the control is set, a sign based comaprison has to be
> performed.
>
> Right now we would inject wrong interrupts and ignore interrupt
> conditions. Also the sleep time is calculated in a wrong way.
>
> Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
> ---
>
> We might be able to drop the checks for "test_kvm_facility(vcpu->kvm, 139)",
> as the architecture states:
>
> "When the multiple-epoch facility is not installed in the configuration
> and the clock-comparator sign control is one, it is unpredictable whether
> the comparison follows the rules of unsigned or signed binary arithmetic."
>
> Have no machine to test this with :(
It will be somewhat hard to test anyway since the compare only differs for the
case where one value (TOD or CKC) is before the 2042 date and the other one is
after. have to think about a good test without needing an LPAR that is close
to the wraparound.
>
> arch/s390/kvm/interrupt.c | 32 ++++++++++++++++++++++++++------
> 1 file changed, 26 insertions(+), 6 deletions(-)
>
> diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c
> index 024ad8bcc516..6566a853c0b8 100644
> --- a/arch/s390/kvm/interrupt.c
> +++ b/arch/s390/kvm/interrupt.c
> @@ -170,7 +170,16 @@ static int ckc_interrupts_enabled(struct kvm_vcpu *vcpu)
>
> static int ckc_irq_pending(struct kvm_vcpu *vcpu)
> {
> - if (vcpu->arch.sie_block->ckc >= kvm_s390_get_tod_clock_fast(vcpu->kvm))
> + int64_t ckc, tod;
> +
> + if (vcpu->arch.sie_block->gcr[0] & 0x0020000000000000ul &&
> + test_kvm_facility(vcpu->kvm, 139)) {
> + ckc = vcpu->arch.sie_block->ckc;
> + tod = kvm_s390_get_tod_clock_fast(vcpu->kvm);
> + if (ckc >= tod)
> + return 0;
> + } else if (vcpu->arch.sie_block->ckc >=
> + kvm_s390_get_tod_clock_fast(vcpu->kvm))
> return 0;
Instead of changing the compare depending on another compare, maybe adding
0x8000000000000000 to the unsigned values makes the change easier to grasp.
On the other hand your code is closer to POP.
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