linux-kernel - [PATCH v2 11/13] KVM: s390: pv: module parameter to fence lazy destroy

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Message-Id: <20210728142631.41860-12-imbrenda@linux.ibm.com>
Date:   Wed, 28 Jul 2021 16:26:29 +0200
From:   Claudio Imbrenda <imbrenda@...ux.ibm.com>
To:     kvm@...r.kernel.org
Cc:     cohuck@...hat.com, borntraeger@...ibm.com, frankja@...ux.ibm.com,
        thuth@...hat.com, pasic@...ux.ibm.com, david@...hat.com,
        linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v2 11/13] KVM: s390: pv: module parameter to fence lazy destroy

Add the module parameter "lazy_destroy", to allow the lazy destroy
mechanism to be switched off. This might be useful for debugging
purposes.

The parameter is enabled by default.

Signed-off-by: Claudio Imbrenda <imbrenda@...ux.ibm.com>
Reviewed-by: Janosch Frank <frankja@...ux.ibm.com>
---
 arch/s390/kvm/pv.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/arch/s390/kvm/pv.c b/arch/s390/kvm/pv.c
index 950053a4efeb..088b94512af3 100644
--- a/arch/s390/kvm/pv.c
+++ b/arch/s390/kvm/pv.c
@@ -26,6 +26,10 @@ struct deferred_priv {
 	unsigned long stor_base;
 };
 
+static int lazy_destroy = 1;
+module_param(lazy_destroy, int, 0444);
+MODULE_PARM_DESC(lazy_destroy, "Deferred destroy for protected guests");
+
 int kvm_s390_pv_destroy_cpu(struct kvm_vcpu *vcpu, u16 *rc, u16 *rrc)
 {
 	int cc = 0;
@@ -361,6 +365,9 @@ int kvm_s390_pv_deinit_vm_deferred(struct kvm *kvm, u16 *rc, u16 *rrc)
 {
 	struct deferred_priv *priv;
 
+	if (!lazy_destroy)
+		return kvm_s390_pv_deinit_vm_now(kvm, rc, rrc);
+
 	priv = kmalloc(sizeof(*priv), GFP_KERNEL | __GFP_ZERO);
 	if (!priv)
 		return kvm_s390_pv_deinit_vm_now(kvm, rc, rrc);
@@ -409,6 +416,12 @@ int kvm_s390_pv_init_vm(struct kvm *kvm, u16 *rc, u16 *rrc)
 	/* Outputs */
 	kvm->arch.pv.handle = uvcb.guest_handle;
 
+	if (!lazy_destroy) {
+		mmap_write_lock(kvm->mm);
+		kvm->mm->context.pv_sync_destroy = 1;
+		mmap_write_unlock(kvm->mm);
+	}
+
 	atomic_inc(&kvm->mm->context.is_protected);
 	if (cc) {
 		if (uvcb.header.rc & UVC_RC_NEED_DESTROY) {
-- 
2.31.1