Thread (9 messages) 9 messages, 2 authors, 2026-03-04
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[PATCH net-next 3/6] net: mana: Introduce GIC context with refcounting for interrupt management

From: Long Li <longli@microsoft.com>
Date: 2026-02-28 02:11:55
Also in: linux-hyperv, linux-rdma, lkml
Subsystem: hyper-v/azure core and drivers, networking drivers, networking [general], the rest · Maintainers: "K. Y. Srinivasan", Haiyang Zhang, Wei Liu, Dexuan Cui, Long Li, Andrew Lunn, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds

To allow Ethernet EQs to use dedicated or shared MSI-X vectors and RDMA
EQs to share the same MSI-X, introduce a GIC (GDMA IRQ Context) with
reference counting. This allows the driver to create an interrupt context
on an assigned or unassigned MSI-X vector and share it across multiple
EQ consumers.

Signed-off-by: Long Li <longli@microsoft.com>
---
 .../net/ethernet/microsoft/mana/gdma_main.c   | 158 ++++++++++++++++++
 include/net/mana/gdma.h                       |  10 ++
 2 files changed, 168 insertions(+)
diff --git a/drivers/net/ethernet/microsoft/mana/gdma_main.c b/drivers/net/ethernet/microsoft/mana/gdma_main.c
index 62e3a2eb68e0..e9b839259c01 100644
--- a/drivers/net/ethernet/microsoft/mana/gdma_main.c
+++ b/drivers/net/ethernet/microsoft/mana/gdma_main.c
@@ -1558,6 +1558,163 @@ static irqreturn_t mana_gd_intr(int irq, void *arg)
 	return IRQ_HANDLED;
 }
 
+void mana_gd_put_gic(struct gdma_context *gc, bool use_msi_bitmap, int msi)
+{
+	struct pci_dev *dev = to_pci_dev(gc->dev);
+	struct msi_map irq_map;
+	struct gdma_irq_context *gic;
+	int irq;
+
+	mutex_lock(&gc->gic_mutex);
+
+	gic = xa_load(&gc->irq_contexts, msi);
+	if (WARN_ON(!gic)) {
+		mutex_unlock(&gc->gic_mutex);
+		return;
+	}
+
+	if (use_msi_bitmap)
+		gic->bitmap_refs--;
+
+	if (use_msi_bitmap && gic->bitmap_refs == 0)
+		clear_bit(msi, gc->msi_bitmap);
+
+	if (!refcount_dec_and_test(&gic->refcount))
+		goto out;
+
+	irq = pci_irq_vector(dev, msi);
+
+	irq_update_affinity_hint(irq, NULL);
+	free_irq(irq, gic);
+
+	if (pci_msix_can_alloc_dyn(dev)) {
+		irq_map.virq = irq;
+		irq_map.index = msi;
+		pci_msix_free_irq(dev, irq_map);
+	}
+
+	xa_erase(&gc->irq_contexts, msi);
+	kfree(gic);
+
+out:
+	mutex_unlock(&gc->gic_mutex);
+}
+EXPORT_SYMBOL_NS(mana_gd_put_gic, "NET_MANA");
+
+/*
+ * Get a GIC (GDMA IRQ Context) on a MSI vector
+ * a MSI can be shared between different EQs, this function supports setting
+ * up separate MSIs using a bitmap, or directly using the MSI index
+ *
+ * @use_msi_bitmap:
+ * True if MSI is assigned by this function on available slots from bitmap.
+ * False if MSI is passed from *msi_requested
+ */
+struct gdma_irq_context *mana_gd_get_gic(struct gdma_context *gc,
+					 bool use_msi_bitmap,
+					 int *msi_requested)
+{
+	struct gdma_irq_context *gic;
+	struct pci_dev *dev = to_pci_dev(gc->dev);
+	struct msi_map irq_map = { };
+	int irq;
+	int msi;
+	int err;
+
+	mutex_lock(&gc->gic_mutex);
+
+	if (use_msi_bitmap) {
+		msi = find_first_zero_bit(gc->msi_bitmap, gc->num_msix_usable);
+		if (msi >= gc->num_msix_usable) {
+			dev_err(gc->dev, "No free MSI vectors available\n");
+			gic = NULL;
+			goto out;
+		}
+		*msi_requested = msi;
+	} else {
+		msi = *msi_requested;
+	}
+
+	gic = xa_load(&gc->irq_contexts, msi);
+	if (gic) {
+		refcount_inc(&gic->refcount);
+		if (use_msi_bitmap) {
+			gic->bitmap_refs++;
+			set_bit(msi, gc->msi_bitmap);
+		}
+		goto out;
+	}
+
+	irq = pci_irq_vector(dev, msi);
+	if (irq == -EINVAL) {
+		irq_map = pci_msix_alloc_irq_at(dev, msi, NULL);
+		if (!irq_map.virq) {
+			err = irq_map.index;
+			dev_err(gc->dev,
+				"Failed to alloc irq_map msi %d err %d\n",
+				msi, err);
+			gic = NULL;
+			goto out;
+		}
+		irq = irq_map.virq;
+		msi = irq_map.index;
+	}
+
+	gic = kzalloc(sizeof(*gic), GFP_KERNEL);
+	if (!gic) {
+		if (irq_map.virq)
+			pci_msix_free_irq(dev, irq_map);
+		goto out;
+	}
+
+	gic->handler = mana_gd_process_eq_events;
+	gic->msi = msi;
+	gic->irq = irq;
+	INIT_LIST_HEAD(&gic->eq_list);
+	spin_lock_init(&gic->lock);
+
+	if (!gic->msi)
+		snprintf(gic->name, MANA_IRQ_NAME_SZ, "mana_hwc@pci:%s",
+			 pci_name(dev));
+	else
+		snprintf(gic->name, MANA_IRQ_NAME_SZ, "mana_msi%d@pci:%s",
+			 gic->msi, pci_name(dev));
+
+	err = request_irq(irq, mana_gd_intr, 0, gic->name, gic);
+	if (err) {
+		dev_err(gc->dev, "Failed to request irq %d %s\n",
+			irq, gic->name);
+		kfree(gic);
+		gic = NULL;
+		if (irq_map.virq)
+			pci_msix_free_irq(dev, irq_map);
+		goto out;
+	}
+
+	refcount_set(&gic->refcount, 1);
+	gic->bitmap_refs = use_msi_bitmap ? 1 : 0;
+
+	err = xa_err(xa_store(&gc->irq_contexts, msi, gic, GFP_KERNEL));
+	if (err) {
+		dev_err(gc->dev, "Failed to store irq context for msi %d: %d\n",
+			msi, err);
+		free_irq(irq, gic);
+		kfree(gic);
+		gic = NULL;
+		if (irq_map.virq)
+			pci_msix_free_irq(dev, irq_map);
+		goto out;
+	}
+
+	if (use_msi_bitmap)
+		set_bit(msi, gc->msi_bitmap);
+
+out:
+	mutex_unlock(&gc->gic_mutex);
+	return gic;
+}
+EXPORT_SYMBOL_NS(mana_gd_get_gic, "NET_MANA");
+
 int mana_gd_alloc_res_map(u32 res_avail, struct gdma_resource *r)
 {
 	r->map = bitmap_zalloc(res_avail, GFP_KERNEL);
@@ -2040,6 +2197,7 @@ static int mana_gd_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
 		goto release_region;
 
 	mutex_init(&gc->eq_test_event_mutex);
+	mutex_init(&gc->gic_mutex);
 	pci_set_drvdata(pdev, gc);
 	gc->bar0_pa = pci_resource_start(pdev, 0);
 
diff --git a/include/net/mana/gdma.h b/include/net/mana/gdma.h
index 477b751f124e..be6bdd169b3d 100644
--- a/include/net/mana/gdma.h
+++ b/include/net/mana/gdma.h
@@ -382,6 +382,10 @@ struct gdma_irq_context {
 	spinlock_t lock;
 	struct list_head eq_list;
 	char name[MANA_IRQ_NAME_SZ];
+	unsigned int msi;
+	unsigned int irq;
+	refcount_t refcount;
+	unsigned int bitmap_refs;
 };
 
 enum gdma_context_flags {
@@ -441,6 +445,9 @@ struct gdma_context {
 
 	unsigned long		flags;
 
+	/* Protect access to GIC context */
+	struct mutex		gic_mutex;
+
 	/* Indicate if this device is sharing MSI for EQs on MANA */
 	bool msi_sharing;
 
@@ -1007,6 +1014,9 @@ int mana_gd_resume(struct pci_dev *pdev);
 
 bool mana_need_log(struct gdma_context *gc, int err);
 
+struct gdma_irq_context *mana_gd_get_gic(struct gdma_context *gc, bool use_msi_bitmap,
+					 int *msi_requested);
+void mana_gd_put_gic(struct gdma_context *gc, bool use_msi_bitmap, int msi);
 int mana_gd_query_device_cfg(struct gdma_context *gc, u32 proto_major_ver,
 			     u32 proto_minor_ver, u32 proto_micro_ver,
 			     u16 *max_num_vports, u8 *bm_hostmode);
-- 
2.43.0
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