linux-kernel - [RFC PATCH 03/34] KVM: irqfd: Allow KVM backends to override IRQ injection via set

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Message-Id: <20250424141341.841734-4-karim.manaouil@linaro.org>
Date: Thu, 24 Apr 2025 15:13:10 +0100
From: Karim Manaouil <karim.manaouil@...aro.org>
To: linux-kernel@...r.kernel.org,
	kvm@...r.kernel.org,
	linux-arm-msm@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	kvmarm@...ts.linux.dev
Cc: Karim Manaouil <karim.manaouil@...aro.org>,
	Alexander Graf <graf@...zon.com>,
	Alex Elder <elder@...nel.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Fuad Tabba <tabba@...gle.com>,
	Joey Gouly <joey.gouly@....com>,
	Jonathan Corbet <corbet@....net>,
	Marc Zyngier <maz@...nel.org>,
	Mark Brown <broonie@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Oliver Upton <oliver.upton@...ux.dev>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Prakruthi Deepak Heragu <quic_pheragu@...cinc.com>,
	Quentin Perret <qperret@...gle.com>,
	Rob Herring <robh@...nel.org>,
	Srinivas Kandagatla <srini@...nel.org>,
	Srivatsa Vaddagiri <quic_svaddagi@...cinc.com>,
	Will Deacon <will@...nel.org>,
	Haripranesh S <haripran@....qualcomm.com>,
	Carl van Schaik <cvanscha@....qualcomm.com>,
	Murali Nalajala <mnalajal@...cinc.com>,
	Sreenivasulu Chalamcharla <sreeniva@....qualcomm.com>,
	Trilok Soni <tsoni@...cinc.com>,
	Stefan Schmidt <stefan.schmidt@...aro.org>
Subject: [RFC PATCH 03/34] KVM: irqfd: Allow KVM backends to override IRQ injection via set_irq callback

Some KVM backends, such as Gunyah, require custom mechanisms to inject
interrupts into the guest. For example, Gunyah performs IRQ injection
through a hypercall to the underlying hypervisor.

To support such use case, this patch introduces a new optional callback
field `set_irq` in `struct kvm_kernel_irqfd`. If this callback is set,
irqfd injection will use the provided function instead of calling
kvm_set_irq() directly.

The default behavior is unchanged for existing users that do not override
the `set_irq` field.

Signed-off-by: Karim Manaouil <karim.manaouil@...aro.org>
---
 include/linux/kvm_irqfd.h | 1 +
 virt/kvm/eventfd.c        | 5 +++++
 2 files changed, 6 insertions(+)

diff --git a/include/linux/kvm_irqfd.h b/include/linux/kvm_irqfd.h
index e8d21d443c58..7d54bc12c4bf 100644
--- a/include/linux/kvm_irqfd.h
+++ b/include/linux/kvm_irqfd.h
@@ -46,6 +46,7 @@ struct kvm_kernel_irqfd {
 	/* Used for level IRQ fast-path */
 	int gsi;
 	struct work_struct inject;
+	int (*set_irq)(struct kvm_kernel_irqfd *);
 	/* The resampler used by this irqfd (resampler-only) */
 	struct kvm_kernel_irqfd_resampler *resampler;
 	/* Eventfd notified on resample (resampler-only) */
diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c
index 5f3776a1b960..d6702225e7f2 100644
--- a/virt/kvm/eventfd.c
+++ b/virt/kvm/eventfd.c
@@ -63,6 +63,11 @@ irqfd_inject(struct work_struct *work)
 		container_of(work, struct kvm_kernel_irqfd, inject);
 	struct kvm *kvm = irqfd->kvm;
 
+	if (irqfd->set_irq) {
+		irqfd->set_irq(irqfd);
+		return;
+	}
+
 	if (!irqfd->resampler) {
 		kvm_set_irq(kvm, KVM_USERSPACE_IRQ_SOURCE_ID, irqfd->gsi, 1,
 				false);
-- 
2.39.5