Messages in this thread Patch in this message | | | From | Ilya Leoshkevich <> | Subject | [PATCH v2 4/6] KVM: s390: interrupt: Fix single-stepping userspace-emulated instructions | Date | Fri, 21 Jul 2023 13:57:57 +0200 |
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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 before KVM_EXIT_S390_SIEIC.
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com> --- arch/s390/kvm/kvm-s390.c | 16 +++++++++++++--- 1 file changed, 13 insertions(+), 3 deletions(-)
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c index 0c6333b108ba..b717fb8cffed 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 +5402,18 @@ 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; + + if (!rc) + vcpu->guest_debug &= ~KVM_GUESTDBG_EXIT_PENDING; + + return rc; } static int kvm_s390_handle_pv_vcpu_dump(struct kvm_vcpu *vcpu, -- 2.41.0
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