[v2] KVM: s390: interrupt: Fix stepping into interrupt handlers

[PATCH v2 5/6] KVM: s390: interrupt: Fix single-stepping ISKE

Posted by Ilya Leoshkevich 2 years, 6 months ago

kvm_s390_skey_check_enable() does not emulate any instructions, rather,
it clears CPUSTAT_KSS and arranges for ISKE to run again. Therefore,
skip the PER check and let ISKE run happen. Otherwise a debugger will
see two single-step events on the same ISKE.

Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
---
 arch/s390/kvm/intercept.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/s390/kvm/intercept.c b/arch/s390/kvm/intercept.c
index d2f7940c5d03..8793cec066a6 100644
--- a/arch/s390/kvm/intercept.c
+++ b/arch/s390/kvm/intercept.c
@@ -630,8 +630,7 @@ int kvm_handle_sie_intercept(struct kvm_vcpu *vcpu)
 		rc = handle_partial_execution(vcpu);
 		break;
 	case ICPT_KSS:
-		rc = kvm_s390_skey_check_enable(vcpu);
-		break;
+		return kvm_s390_skey_check_enable(vcpu);
 	case ICPT_MCHKREQ:
 	case ICPT_INT_ENABLE:
 		/*
-- 
2.41.0

Re: [PATCH v2 5/6] KVM: s390: interrupt: Fix single-stepping ISKE

Posted by David Hildenbrand 2 years, 6 months ago

On 21.07.23 13:57, Ilya Leoshkevich wrote:
> kvm_s390_skey_check_enable() does not emulate any instructions, rather,
> it clears CPUSTAT_KSS and arranges for ISKE to run again. Therefore,
> skip the PER check and let ISKE run happen. Otherwise a debugger will
> see two single-step events on the same ISKE.
> 
> Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
> ---
>   arch/s390/kvm/intercept.c | 3 +--
>   1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/arch/s390/kvm/intercept.c b/arch/s390/kvm/intercept.c
> index d2f7940c5d03..8793cec066a6 100644
> --- a/arch/s390/kvm/intercept.c
> +++ b/arch/s390/kvm/intercept.c
> @@ -630,8 +630,7 @@ int kvm_handle_sie_intercept(struct kvm_vcpu *vcpu)
>   		rc = handle_partial_execution(vcpu);
>   		break;
>   	case ICPT_KSS:
> -		rc = kvm_s390_skey_check_enable(vcpu);
> -		break;
> +		return kvm_s390_skey_check_enable(vcpu);
>   	case ICPT_MCHKREQ:
>   	case ICPT_INT_ENABLE:
>   		/*

Reviewed-by: David Hildenbrand <david@redhat.com>

-- 
Cheers,

David / dhildenb

Re: [PATCH v2 5/6] KVM: s390: interrupt: Fix single-stepping ISKE

Posted by Christian Borntraeger 2 years, 6 months ago


Am 21.07.23 um 13:57 schrieb Ilya Leoshkevich:
> kvm_s390_skey_check_enable() does not emulate any instructions, rather,
> it clears CPUSTAT_KSS and arranges for ISKE to run again. Therefore,
> skip the PER check and let ISKE run happen. Otherwise a debugger will
> see two single-step events on the same ISKE.

The same would be true for all instruction triggering a keyless mode exit,
like SSKE, RRBE but also LPSWE with a keyed PSW, no?
> 
> Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>

Reviewed-by: Christian Borntraeger <borntraeger@linux.ibm.com>
> ---
>   arch/s390/kvm/intercept.c | 3 +--
>   1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/arch/s390/kvm/intercept.c b/arch/s390/kvm/intercept.c
> index d2f7940c5d03..8793cec066a6 100644
> --- a/arch/s390/kvm/intercept.c
> +++ b/arch/s390/kvm/intercept.c
> @@ -630,8 +630,7 @@ int kvm_handle_sie_intercept(struct kvm_vcpu *vcpu)
>   		rc = handle_partial_execution(vcpu);
>   		break;
>   	case ICPT_KSS:
> -		rc = kvm_s390_skey_check_enable(vcpu);
> -		break;

maybe add a comment here: /* Instruction will be redriven, skip the PER check */
> +		return kvm_s390_skey_check_enable(vcpu);

>   	case ICPT_MCHKREQ:
>   	case ICPT_INT_ENABLE:
>   		/*