KVM: s390: no timer interrupts when single-stepping a guest
When a guest is single-stepped, we want to disable timer interrupts. Otherwise,
the guest will continuously execute the external interrupt handler and make
debugging of code where timer interrupts are enabled almost impossible.
The delivery of timer interrupts can be enforced in such sections by setting a
breakpoint and continuing execution.
In order to disable timer interrupts, they are disabled in the control register
of the guest just before SIE entry and are suppressed in the interrupt
check/delivery methods.
Signed-off-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c
index 0165f1b..d020c5f 100644
--- a/arch/s390/kvm/interrupt.c
+++ b/arch/s390/kvm/interrupt.c
@@ -61,6 +61,9 @@
if (psw_extint_disabled(vcpu) ||
!(vcpu->arch.sie_block->gcr[0] & 0x800ul))
return 0;
+ if (guestdbg_enabled(vcpu) && guestdbg_sstep_enabled(vcpu))
+ /* No timer interrupts when single stepping */
+ return 0;
return 1;
}