On 24.07.23 11:44, Ilya Leoshkevich wrote:
Single-stepping a userspace-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 after arranging a KVM_EXIT_S390_SIEIC exit, kvm_handle_sie_intercept() calls kvm_s390_handle_per_ifetch_icpt(), which sets KVM_GUESTDBG_EXIT_PENDING. This bit, however, is not processed immediately, but rather persists until the next ioctl(), causing a spurious single-step exit. Fix by clearing this bit in ioctl(). Signed-off-by: Ilya Leoshkevich <iii@xxxxxxxxxxxxx> --- arch/s390/kvm/kvm-s390.c | 23 ++++++++++++++++++++--- 1 file changed, 20 insertions(+), 3 deletions(-) diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c index 0c6333b108ba..e6511608280c 100644 --- a/arch/s390/kvm/kvm-s390.c +++ b/arch/s390/kvm/kvm-s390.c @@ -5383,6 +5383,7 @@ long kvm_arch_vcpu_async_ioctl(struct file *filp, { struct kvm_vcpu *vcpu = filp->private_data; void __user *argp = (void __user *)arg; + int rc;switch (ioctl) {case KVM_S390_IRQ: { @@ -5390,7 +5391,8 @@ long kvm_arch_vcpu_async_ioctl(struct file *filp,if (copy_from_user(&s390irq, argp, sizeof(s390irq)))return -EFAULT; - return kvm_s390_inject_vcpu(vcpu, &s390irq); + rc = kvm_s390_inject_vcpu(vcpu, &s390irq); + break; } case KVM_S390_INTERRUPT: { struct kvm_s390_interrupt s390int; @@ -5400,10 +5402,25 @@ long kvm_arch_vcpu_async_ioctl(struct file *filp, return -EFAULT; if (s390int_to_s390irq(&s390int, &s390irq)) return -EINVAL; - return kvm_s390_inject_vcpu(vcpu, &s390irq); + rc = kvm_s390_inject_vcpu(vcpu, &s390irq); + break; } + default: + rc = -ENOIOCTLCMD; + break; } - return -ENOIOCTLCMD; + + /* + * To simplify single stepping of userspace-emulated instructions, + * KVM_EXIT_S390_SIEIC exit sets KVM_GUESTDBG_EXIT_PENDING (see + * should_handle_per_ifetch()). However, if userspace emulation injects + * an interrupt, it needs to be cleared, so that KVM_EXIT_DEBUG happens + * after (and not before) the interrupt delivery. + */ + if (!rc) + vcpu->guest_debug &= ~KVM_GUESTDBG_EXIT_PENDING; + + return rc; }static int kvm_s390_handle_pv_vcpu_dump(struct kvm_vcpu *vcpu,
Reviewed-by: David Hildenbrand <david@xxxxxxxxxx> -- Cheers, David / dhildenb
