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KVM: s390: interrupt: Fix single-stepping kernel-emulated instructions

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Single-stepping a kernel-emulated instruction that generates an
interrupt causes GDB to land on the instruction following it instead of
the respective interrupt handler.

The reason is that kvm_handle_sie_intercept(), after injecting the
interrupt, also processes the PER event and arranges a KVM_SINGLESTEP
exit. The interrupt is not yet delivered, however, so the userspace
sees the next instruction.

Fix by avoiding the KVM_SINGLESTEP exit when there is a pending
interrupt. The next __vcpu_run() loop iteration will arrange a
KVM_SINGLESTEP exit after delivering the interrupt.

Reviewed-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: <20230725143857.228626-4-iii@linux.ibm.com>
Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
This commit is contained in:
Ilya Leoshkevich 2023-07-25 16:37:18 +02:00 committed by Janosch Frank
parent 74a439ef7b
commit ba853a4e1c
1 changed files with 14 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

17
arch/s390/kvm/intercept.c
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@ -583,6 +583,19 @@ static int handle_pv_notification(struct kvm_vcpu *vcpu)
return handle_instruction(vcpu);
}
static bool should_handle_per_ifetch(const struct kvm_vcpu *vcpu, int rc)
{
/* Process PER, also if the instruction is processed in user space. */
if (!(vcpu->arch.sie_block->icptstatus & 0x02))
return false;
if (rc != 0 && rc != -EOPNOTSUPP)
return false;
if (guestdbg_sstep_enabled(vcpu) && vcpu->arch.local_int.pending_irqs)
/* __vcpu_run() will exit after delivering the interrupt. */
return false;
return true;
}
int kvm_handle_sie_intercept(struct kvm_vcpu *vcpu)
{
int rc, per_rc = 0;
@ -645,9 +658,7 @@ int kvm_handle_sie_intercept(struct kvm_vcpu *vcpu)
return -EOPNOTSUPP;
}
/* process PER, also if the instruction is processed in user space */
if (vcpu->arch.sie_block->icptstatus & 0x02 &&
(!rc || rc == -EOPNOTSUPP))
if (should_handle_per_ifetch(vcpu, rc))
per_rc = kvm_s390_handle_per_ifetch_icpt(vcpu);
return per_rc ? per_rc : rc;
}