Commit 74a439ef authored Jul 25, 2023 by Ilya Leoshkevich Committed by Janosch Frank Aug 28, 2023

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



Currently, after single-stepping an instruction that generates a
specification exception, GDB ends up on the instruction immediately
following it.

The reason is that vcpu_post_run() injects the interrupt and sets
KVM_GUESTDBG_EXIT_PENDING, causing a KVM_SINGLESTEP exit. The
interrupt is not delivered, however, therefore userspace sees the
address of the next instruction.

Fix by letting the __vcpu_run() loop go into the next iteration,
where vcpu_pre_run() delivers the interrupt and sets
KVM_GUESTDBG_EXIT_PENDING.

Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Message-ID: <20230725143857.228626-3-iii@linux.ibm.com>
Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Signed-off-by: Janosch Frank <frankja@linux.ibm.com>

parent 16631c42

arch/s390/kvm/intercept.c

+16 −1

Original line number	Diff line number	Diff line
		@@ -228,6 +228,21 @@ static int handle_itdb(struct kvm_vcpu *vcpu)

		#define per_event(vcpu) (vcpu->arch.sie_block->iprcc & PGM_PER)

		static bool should_handle_per_event(const struct kvm_vcpu *vcpu)
		{
		if (!guestdbg_enabled(vcpu) \|\| !per_event(vcpu))
		return false;
		if (guestdbg_sstep_enabled(vcpu) &&
		vcpu->arch.sie_block->iprcc != PGM_PER) {
		/*
		* __vcpu_run() will exit after delivering the concurrently
		* indicated condition.
		*/
		return false;
		}
		return true;
		}

		static int handle_prog(struct kvm_vcpu *vcpu)
		{
		psw_t psw;
		@@ -242,7 +257,7 @@ static int handle_prog(struct kvm_vcpu *vcpu)
		if (kvm_s390_pv_cpu_is_protected(vcpu))
		return -EOPNOTSUPP;

		if (guestdbg_enabled(vcpu) && per_event(vcpu)) {
		if (should_handle_per_event(vcpu)) {
		rc = kvm_s390_handle_per_event(vcpu);
		if (rc)
		return rc;