linux-kernel - [PATCH v3 2/4] KVM: s390: remove unneeded srcu lock

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Message-ID: <20250522132259.167708-3-imbrenda@linux.ibm.com>
Date: Thu, 22 May 2025 15:22:57 +0200
From: Claudio Imbrenda <imbrenda@...ux.ibm.com>
To: linux-kernel@...r.kernel.org
Cc: kvm@...r.kernel.org, linux-s390@...r.kernel.org, frankja@...ux.ibm.com,
        borntraeger@...ibm.com, seiden@...ux.ibm.com, nsg@...ux.ibm.com,
        nrb@...ux.ibm.com, david@...hat.com, hca@...ux.ibm.com,
        agordeev@...ux.ibm.com, svens@...ux.ibm.com, gor@...ux.ibm.com,
        schlameuss@...ux.ibm.com
Subject: [PATCH v3 2/4] KVM: s390: remove unneeded srcu lock

All paths leading to handle_essa() already hold the kvm->srcu.
Remove unneeded srcu locking from handle_essa().
Add lockdep assertion to make sure we will always be holding kvm->srcu
when entering handle_essa().

Signed-off-by: Claudio Imbrenda <imbrenda@...ux.ibm.com>
Reviewed-by: Nina Schoetterl-Glausch <nsg@...ux.ibm.com>
Reviewed-by: Christian Borntraeger <borntraeger@...ux.ibm.com>
---
 arch/s390/kvm/priv.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/arch/s390/kvm/priv.c b/arch/s390/kvm/priv.c
index 1a49b89706f8..9253c70897a8 100644
--- a/arch/s390/kvm/priv.c
+++ b/arch/s390/kvm/priv.c
@@ -1248,6 +1248,8 @@ static inline int __do_essa(struct kvm_vcpu *vcpu, const int orc)
 
 static int handle_essa(struct kvm_vcpu *vcpu)
 {
+	lockdep_assert_held(&vcpu->kvm->srcu);
+
 	/* entries expected to be 1FF */
 	int entries = (vcpu->arch.sie_block->cbrlo & ~PAGE_MASK) >> 3;
 	unsigned long *cbrlo;
@@ -1297,12 +1299,8 @@ static int handle_essa(struct kvm_vcpu *vcpu)
 		/* Retry the ESSA instruction */
 		kvm_s390_retry_instr(vcpu);
 	} else {
-		int srcu_idx;
-
 		mmap_read_lock(vcpu->kvm->mm);
-		srcu_idx = srcu_read_lock(&vcpu->kvm->srcu);
 		i = __do_essa(vcpu, orc);
-		srcu_read_unlock(&vcpu->kvm->srcu, srcu_idx);
 		mmap_read_unlock(vcpu->kvm->mm);
 		if (i < 0)
 			return i;
-- 
2.49.0