Re: [PATCH] KVM: s390: only deliver the set service event bits

[Christian Borntraeger <borntraeger@linux.ibm.com>]

Am 05.02.24 um 22:43 schrieb Eric Farman:
> The SCLP driver code masks off the last two bits of the parameter [1]
> to determine if a read is required, but doesn't care about the
> contents of those bits. Meanwhile, the KVM code that delivers
> event interrupts masks off those two bits but sends both to the
> guest, even if only one was specified by userspace [2].
> 
> This works for the driver code, but it means any nuances of those
> bits gets lost. Use the event pending mask as an actual mask, and
> only send the bit(s) that were specified in the pending interrupt.
> 
> [1] Linux: sclp_interrupt_handler() (drivers/s390/char/sclp.c:658)
> [2] QEMU: service_interrupt() (hw/s390x/sclp.c:360..363)
> 
> Fixes: 0890ddea1a90 ("KVM: s390: protvirt: Add SCLP interrupt handling")
> Signed-off-by: Eric Farman <farman@linux.ibm.com>

makes sense

Reviewed-by: Christian Borntraeger <borntraeger@linux.ibm.com>


> ---
>   arch/s390/kvm/interrupt.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c
> index fc4007cc067a..20e080e9150b 100644
> --- a/arch/s390/kvm/interrupt.c
> +++ b/arch/s390/kvm/interrupt.c
> @@ -1031,7 +1031,7 @@ static int __must_check __deliver_service_ev(struct kvm_vcpu *vcpu)
>   		return 0;
>   	}
>   	ext = fi->srv_signal;
> -	/* only clear the event bit */
> +	/* only clear the event bits */
>   	fi->srv_signal.ext_params &= ~SCCB_EVENT_PENDING;
>   	clear_bit(IRQ_PEND_EXT_SERVICE_EV, &fi->pending_irqs);
>   	spin_unlock(&fi->lock);
> @@ -1041,7 +1041,7 @@ static int __must_check __deliver_service_ev(struct kvm_vcpu *vcpu)
>   	trace_kvm_s390_deliver_interrupt(vcpu->vcpu_id, KVM_S390_INT_SERVICE,
>   					 ext.ext_params, 0);
>   
> -	return write_sclp(vcpu, SCCB_EVENT_PENDING);
> +	return write_sclp(vcpu, ext.ext_params & SCCB_EVENT_PENDING);
>   }
>   
>   static int __must_check __deliver_pfault_done(struct kvm_vcpu *vcpu)