linux-kernel - [v2 1/4] KVM: irqchip: add setup empty irq routing function

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Date: Sun, 21 Jan 2024 19:17:27 +0800
From: Yi Wang <up2wing@...il.com>
To: seanjc@...gle.com,
	pbonzini@...hat.com,
	tglx@...utronix.de,
	mingo@...hat.com,
	bp@...en8.de,
	dave.hansen@...ux.intel.com,
	x86@...nel.org,
	hpa@...or.com,
	kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	wanpengli@...cent.com,
	foxywang@...cent.com,
	oliver.upton@...ux.dev,
	maz@...nel.org,
	anup@...infault.org,
	atishp@...shpatra.org,
	borntraeger@...ux.ibm.com,
	frankja@...ux.ibm.com,
	imbrenda@...ux.ibm.com
Cc: up2wing@...il.com
Subject: [v2 1/4] KVM: irqchip: add setup empty irq routing function

Add a new function to setup empty irq routing in kvm path, which
can be invoded in non-architecture-specific functions. The difference
compared to the kvm_setup_empty_irq_routing() is this function just
alloc the empty irq routing and does not need synchronize srcu, as
we will call it in kvm_create_vm().

This patch is a preparatory step for an upcoming patch to avoid
delay in KVM_CAP_SPLIT_IRQCHIP ioctl.

Signed-off-by: Yi Wang <foxywang@...cent.com>
---
 include/linux/kvm_host.h |  1 +
 virt/kvm/irqchip.c       | 19 +++++++++++++++++++
 2 files changed, 20 insertions(+)

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 4944136efaa2..e91525c0a4ea 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -2000,6 +2000,7 @@ int kvm_set_irq_routing(struct kvm *kvm,
 			const struct kvm_irq_routing_entry *entries,
 			unsigned nr,
 			unsigned flags);
+int kvm_setup_empty_irq_routing_lockless(struct kvm *kvm);
 int kvm_set_routing_entry(struct kvm *kvm,
 			  struct kvm_kernel_irq_routing_entry *e,
 			  const struct kvm_irq_routing_entry *ue);
diff --git a/virt/kvm/irqchip.c b/virt/kvm/irqchip.c
index 1e567d1f6d3d..90fc43bd0fe4 100644
--- a/virt/kvm/irqchip.c
+++ b/virt/kvm/irqchip.c
@@ -237,3 +237,22 @@ int kvm_set_irq_routing(struct kvm *kvm,
 
 	return r;
 }
+
+int kvm_setup_empty_irq_routing_lockless(struct kvm *kvm)
+{
+	struct kvm_irq_routing_table *new;
+	u32 i, j;
+
+	new = kzalloc(struct_size(new, map, 1), GFP_KERNEL_ACCOUNT);
+	if (!new)
+		return -ENOMEM;
+
+	new->nr_rt_entries = 1;
+	for (i = 0; i < KVM_NR_IRQCHIPS; i++)
+		for (j = 0; j < KVM_IRQCHIP_NUM_PINS; j++)
+			new->chip[i][j] = -1;
+
+	RCU_INIT_POINTER(kvm->irq_routing, new);
+
+	return 0;
+}
-- 
2.39.3