linux-kernel - [PATCH v4 5/6] KVM: s390: interrupt: Fix single-stepping keyless mode exits

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Message-ID: <20230725143857.228626-6-iii@linux.ibm.com>
Date:   Tue, 25 Jul 2023 16:37:20 +0200
From:   Ilya Leoshkevich <iii@...ux.ibm.com>
To:     Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Janosch Frank <frankja@...ux.ibm.com>,
        Claudio Imbrenda <imbrenda@...ux.ibm.com>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>
Cc:     David Hildenbrand <david@...hat.com>,
        Sven Schnelle <svens@...ux.ibm.com>, kvm@...r.kernel.org,
        linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jens Freimann <jfreimann@...hat.com>,
        Ilya Leoshkevich <iii@...ux.ibm.com>
Subject: [PATCH v4 5/6] KVM: s390: interrupt: Fix single-stepping keyless mode exits

kvm_s390_skey_check_enable() does not emulate any instructions, rather,
it clears CPUSTAT_KSS and arranges the instruction that caused the exit
(e.g., ISKE, SSKE, RRBE or LPSWE with a keyed PSW) to run again.

Therefore, skip the PER check and let the instruction execution happen.
Otherwise, a debugger will see two single-step events on the same
instruction.

Reviewed-by: Christian Borntraeger <borntraeger@...ux.ibm.com>
Reviewed-by: David Hildenbrand <david@...hat.com>
Signed-off-by: Ilya Leoshkevich <iii@...ux.ibm.com>
---
 arch/s390/kvm/intercept.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/s390/kvm/intercept.c b/arch/s390/kvm/intercept.c
index db222c749e5e..9f64f27f086e 100644
--- a/arch/s390/kvm/intercept.c
+++ b/arch/s390/kvm/intercept.c
@@ -630,8 +630,8 @@ 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;
+		/* Instruction will be redriven, skip the PER check. */
+		return kvm_s390_skey_check_enable(vcpu);
 	case ICPT_MCHKREQ:
 	case ICPT_INT_ENABLE:
 		/*
-- 
2.41.0