KVM: s390: interrupt: Fix single-stepping into interrupt handlers

After single-stepping an instruction that generates an interrupt, GDB ends up on the second instruction of the respective interrupt handler. The reason is that vcpu_pre_run() manually delivers the interrupt, and then __vcpu_run() runs the first handler instruction using the CPUSTAT_P flag. This causes a KVM_SINGLESTEP exit on the second handler instruction. Fix by delaying the KVM_SINGLESTEP exit until after the manual interrupt delivery. Acked-by: David Hildenbrand <[email protected]> Reviewed-by: Claudio Imbrenda <[email protected]> Signed-off-by: Ilya Leoshkevich <[email protected]> Message-ID: <[email protected]> Signed-off-by: Claudio Imbrenda <[email protected]> Signed-off-by: Janosch Frank <[email protected]>
torvalds · Aug 28, 2023 · 16631c4 · 16631c4
1 parent ede6d0b
commit 16631c4
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Showing 2 changed files with 16 additions and 2 deletions.
diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c
@@ -1392,6 +1392,7 @@ int __must_check kvm_s390_deliver_pending_interrupts(struct kvm_vcpu *vcpu)
 {
  struct kvm_s390_local_interrupt *li = &vcpu->arch.local_int;
  int rc = 0;
+ bool delivered = false;
  unsigned long irq_type;
  unsigned long irqs;
 
@@ -1465,6 +1466,19 @@ int __must_check kvm_s390_deliver_pending_interrupts(struct kvm_vcpu *vcpu)
  WARN_ONCE(1, "Unknown pending irq type %ld", irq_type);
  clear_bit(irq_type, &li->pending_irqs);
  }
+ delivered |= !rc;
+ }
+
+ /*
+ * We delivered at least one interrupt and modified the PC. Force a
+ * singlestep event now.
+ */
+ if (delivered && guestdbg_sstep_enabled(vcpu)) {
+ struct kvm_debug_exit_arch *debug_exit = &vcpu->run->debug.arch;
+
+ debug_exit->addr = vcpu->arch.sie_block->gpsw.addr;
+ debug_exit->type = KVM_SINGLESTEP;
+ vcpu->guest_debug |= KVM_GUESTDBG_EXIT_PENDING;
  }
 
  set_intercept_indicators(vcpu);

diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
@@ -4611,7 +4611,7 @@ static int vcpu_pre_run(struct kvm_vcpu *vcpu)
 
  if (!kvm_is_ucontrol(vcpu->kvm)) {
  rc = kvm_s390_deliver_pending_interrupts(vcpu);
- if (rc)
+ if (rc || guestdbg_exit_pending(vcpu))
  return rc;
  }
 
@@ -4738,7 +4738,7 @@ static int __vcpu_run(struct kvm_vcpu *vcpu)
 
  do {
  rc = vcpu_pre_run(vcpu);
- if (rc)
+ if (rc || guestdbg_exit_pending(vcpu))
  break;
 
  kvm_vcpu_srcu_read_unlock(vcpu);