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 <david@redhat.com>
Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Message-ID: <20230725143857.228626-2-iii@linux.ibm.com>
Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Signed-off-by: Janosch Frank <frankja@linux.ibm.com>

diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c
index 9bd0a87..85e39f4 100644 (file)
--- 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
index d1e768b..0c6333b 100644 (file)
--- 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);