[PATCH v6 5/5] net: mana: Allocate MSI-X vectors dynamically

Shradha Gupta
2025-06-11T14:11:15Z

Currently, the MANA driver allocates MSI-X vectors statically based on
MANA_MAX_NUM_QUEUES and num_online_cpus() values and in some cases ends
up allocating more vectors than it needs. This is because, by this time
we do not have a HW channel and do not know how many IRQs should be
allocated.

To avoid this, we allocate 1 MSI-X vector during the creation of HWC and
after getting the value supported by hardware, dynamically add the
remaining MSI-X vectors.

Signed-off-by: Shradha Gupta <shradhagupta@linux.microsoft.com>
Reviewed-by: Haiyang Zhang <haiyangz@microsoft.com>
---
Changes in v5:
* Correctly initialized start_irqs, so that it is cleaned properly
* rearranged the cpu_lock to minimize the critical section
---
Changes in v4:
* added BUG_ON at appropriate places
* moved xa_destroy to mana_gd_remove()
* rearragned the cleanup logic in mana_gd_setup_dyn_irqs()
* simplified processing around start_irq_index in mana_gd_setup_irqs()
* return 0 instead of return err as appropriate
---
Changes in v3:
* implemented irq_contexts as xarrays rather than list
* split the patch to create a perparation patch around irq_setup()
* add log when IRQ allocation/setup for remaining IRQs fails
---
Changes in v2:
* Use string 'MSI-X vectors' instead of 'pci vectors'
* make skip-cpu a bool instead of int
* rearrange the comment arout skip_cpu variable appropriately
* update the capability bit for driver indicating dynamic IRQ
* allocation
* enforced max line length to 80
* enforced RCT convention
* initialized gic to NULL, for when there is a possibility of gic
not being populated correctly
---
.../net/ethernet/microsoft/mana/gdma_main.c | 311 +++++++++++++-----
include/net/mana/gdma.h | 8 +-
2 files changed, 235 insertions(+), 84 deletions(-)

diff --git a/drivers/net/ethernet/microsoft/mana/gdma_main.c b/drivers/net/ethernet/microsoft/mana/gdma_main.c
index 6e468c0f2c40..d0040c12b8a2 100644
--- a/drivers/net/ethernet/microsoft/mana/gdma_main.c
+++ b/drivers/net/ethernet/microsoft/mana/gdma_main.c
@@ -6,6 +6,8 @@
#include <linux/pci.h>
#include <linux/utsname.h>
#include <linux/version.h>
+#include <linux/msi.h>
+#include <linux/irqdomain.h>

#include <net/mana/mana.h>

@@ -80,8 +82,15 @@ static int mana_gd_query_max_resources(struct pci_dev *pdev)
return err ? err : -EPROTO;
}

- if (gc->num_msix_usable > resp.max_msix)
- gc->num_msix_usable = resp.max_msix;
+ if (!pci_msix_can_alloc_dyn(pdev)) {
+ if (gc->num_msix_usable > resp.max_msix)
+ gc->num_msix_usable = resp.max_msix;
+ } else {
+ /* If dynamic allocation is enabled we have already allocated
+ * hwc msi
+ */
+ gc->num_msix_usable = min(resp.max_msix, num_online_cpus() + 1);
+ }

if (gc->num_msix_usable <= 1)
return -ENOSPC;
@@ -483,7 +492,9 @@ static int mana_gd_register_irq(struct gdma_queue *queue,
}

queue->eq.msix_index = msi_index;
- gic = &gc->irq_contexts[msi_index];
+ gic = xa_load(&gc->irq_contexts, msi_index);
+ if (WARN_ON(!gic))
+ return -EINVAL;

spin_lock_irqsave(&gic->lock, flags);
list_add_rcu(&queue->entry, &gic->eq_list);
@@ -508,7 +519,10 @@ static void mana_gd_deregiser_irq(struct gdma_queue *queue)
if (WARN_ON(msix_index >= gc->num_msix_usable))
return;

- gic = &gc->irq_contexts[msix_index];
+ gic = xa_load(&gc->irq_contexts, msix_index);
+ if (WARN_ON(!gic))
+ return;
+
spin_lock_irqsave(&gic->lock, flags);
list_for_each_entry_rcu(eq, &gic->eq_list, entry) {
if (queue == eq) {
@@ -1366,47 +1380,108 @@ static int irq_setup(unsigned int *irqs, unsigned int len, int node,
return 0;
}

-static int mana_gd_setup_irqs(struct pci_dev *pdev)
+static int mana_gd_setup_dyn_irqs(struct pci_dev *pdev, int nvec)
{
struct gdma_context *gc = pci_get_drvdata(pdev);
- unsigned int max_queues_per_port;
struct gdma_irq_context *gic;
- unsigned int max_irqs, cpu;
- int start_irq_index = 1;
- int nvec, *irqs, irq;
- int err, i = 0, j;
+ bool skip_first_cpu = false;
+ int *irqs, irq, err, i;

- cpus_read_lock();
- max_queues_per_port = num_online_cpus();
- if (max_queues_per_port > MANA_MAX_NUM_QUEUES)
- max_queues_per_port = MANA_MAX_NUM_QUEUES;
+ irqs = kmalloc_array(nvec, sizeof(int), GFP_KERNEL);
+ if (!irqs)
+ return -ENOMEM;
+
+ /*
+ * While processing the next pci irq vector, we start with index 1,
+ * as IRQ vector at index 0 is already processed for HWC.
+ * However, the population of irqs array starts with index 0, to be
+ * further used in irq_setup()
+ */
+ for (i = 1; i <= nvec; i++) {
+ gic = kzalloc(sizeof(*gic), GFP_KERNEL);
+ if (!gic) {
+ err = -ENOMEM;
+ goto free_irq;
+ }
+ gic->handler = mana_gd_process_eq_events;
+ INIT_LIST_HEAD(&gic->eq_list);
+ spin_lock_init(&gic->lock);

- /* Need 1 interrupt for the Hardware communication Channel (HWC) */
- max_irqs = max_queues_per_port + 1;
+ snprintf(gic->name, MANA_IRQ_NAME_SZ, "mana_q%d@pci:%s",
+ i - 1, pci_name(pdev));

- nvec = pci_alloc_irq_vectors(pdev, 2, max_irqs, PCI_IRQ_MSIX);
- if (nvec < 0) {
- cpus_read_unlock();
- return nvec;
+ /* one pci vector is already allocated for HWC */
+ irqs[i - 1] = pci_irq_vector(pdev, i);
+ if (irqs[i - 1] < 0) {
+ err = irqs[i - 1];
+ goto free_current_gic;
+ }
+
+ err = request_irq(irqs[i - 1], mana_gd_intr, 0, gic->name, gic);
+ if (err)
+ goto free_current_gic;
+
+ xa_store(&gc->irq_contexts, i, gic, GFP_KERNEL);
}
- if (nvec <= num_online_cpus())
- start_irq_index = 0;

- irqs = kmalloc_array((nvec - start_irq_index), sizeof(int), GFP_KERNEL);
- if (!irqs) {
- err = -ENOMEM;
- goto free_irq_vector;
+ /*
+ * When calling irq_setup() for dynamically added IRQs, if number of
+ * CPUs is more than or equal to allocated MSI-X, we need to skip the
+ * first CPU sibling group since they are already affinitized to HWC IRQ
+ */
+ cpus_read_lock();
+ if (gc->num_msix_usable <= num_online_cpus())
+ skip_first_cpu = true;
+
+ err = irq_setup(irqs, nvec, gc->numa_node, skip_first_cpu);
+ if (err) {
+ cpus_read_unlock();
+ goto free_irq;
}

- gc->irq_contexts = kcalloc(nvec, sizeof(struct gdma_irq_context),
- GFP_KERNEL);
- if (!gc->irq_contexts) {
- err = -ENOMEM;
- goto free_irq_array;
+ cpus_read_unlock();
+ kfree(irqs);
+ return 0;
+
+free_current_gic:
+ kfree(gic);
+free_irq:
+ for (i -= 1; i > 0; i--) {
+ irq = pci_irq_vector(pdev, i);
+ gic = xa_load(&gc->irq_contexts, i);
+ if (WARN_ON(!gic))
+ continue;
+
+ irq_update_affinity_hint(irq, NULL);
+ free_irq(irq, gic);
+ xa_erase(&gc->irq_contexts, i);
+ kfree(gic);
}
+ kfree(irqs);
+ return err;
+}
+
+static int mana_gd_setup_irqs(struct pci_dev *pdev, int nvec)
+{
+ struct gdma_context *gc = pci_get_drvdata(pdev);
+ struct gdma_irq_context *gic;
+ int *irqs, *start_irqs, irq;
+ unsigned int cpu;
+ int err, i;
+
+ irqs = kmalloc_array(nvec, sizeof(int), GFP_KERNEL);
+ if (!irqs)
+ return -ENOMEM;
+
+ start_irqs = irqs;

for (i = 0; i < nvec; i++) {
- gic = &gc->irq_contexts[i];
+ gic = kzalloc(sizeof(*gic), GFP_KERNEL);
+ if (!gic) {
+ err = -ENOMEM;
+ goto free_irq;
+ }
+
gic->handler = mana_gd_process_eq_events;
INIT_LIST_HEAD(&gic->eq_list);
spin_lock_init(&gic->lock);
@@ -1418,69 +1493,128 @@ static int mana_gd_setup_irqs(struct pci_dev *pdev)
snprintf(gic->name, MANA_IRQ_NAME_SZ, "mana_q%d@pci:%s",
i - 1, pci_name(pdev));

- irq = pci_irq_vector(pdev, i);
- if (irq < 0) {
- err = irq;
- goto free_irq;
+ irqs[i] = pci_irq_vector(pdev, i);
+ if (irqs[i] < 0) {
+ err = irqs[i];
+ goto free_current_gic;
}

- if (!i) {
- err = request_irq(irq, mana_gd_intr, 0, gic->name, gic);
- if (err)
- goto free_irq;
-
- /* If number of IRQ is one extra than number of online CPUs,
- * then we need to assign IRQ0 (hwc irq) and IRQ1 to
- * same CPU.
- * Else we will use different CPUs for IRQ0 and IRQ1.
- * Also we are using cpumask_local_spread instead of
- * cpumask_first for the node, because the node can be
- * mem only.
- */
- if (start_irq_index) {
- cpu = cpumask_local_spread(i, gc->numa_node);
- irq_set_affinity_and_hint(irq, cpumask_of(cpu));
- } else {
- irqs[start_irq_index] = irq;
- }
- } else {
- irqs[i - start_irq_index] = irq;
- err = request_irq(irqs[i - start_irq_index], mana_gd_intr, 0,
- gic->name, gic);
- if (err)
- goto free_irq;
- }
+ err = request_irq(irqs[i], mana_gd_intr, 0, gic->name, gic);
+ if (err)
+ goto free_current_gic;
+
+ xa_store(&gc->irq_contexts, i, gic, GFP_KERNEL);
}

- err = irq_setup(irqs, nvec - start_irq_index, gc->numa_node, false);
- if (err)
+ /* If number of IRQ is one extra than number of online CPUs,
+ * then we need to assign IRQ0 (hwc irq) and IRQ1 to
+ * same CPU.
+ * Else we will use different CPUs for IRQ0 and IRQ1.
+ * Also we are using cpumask_local_spread instead of
+ * cpumask_first for the node, because the node can be
+ * mem only.
+ */
+ cpus_read_lock();
+ if (nvec > num_online_cpus()) {
+ cpu = cpumask_local_spread(0, gc->numa_node);
+ irq_set_affinity_and_hint(irqs[0], cpumask_of(cpu));
+ irqs++;
+ nvec -= 1;
+ }
+
+ err = irq_setup(irqs, nvec, gc->numa_node, false);
+ if (err) {
+ cpus_read_unlock();
goto free_irq;
+ }

- gc->max_num_msix = nvec;
- gc->num_msix_usable = nvec;
cpus_read_unlock();
- kfree(irqs);
+ kfree(start_irqs);
return 0;

+free_current_gic:
+ kfree(gic);
free_irq:
- for (j = i - 1; j >= 0; j--) {
- irq = pci_irq_vector(pdev, j);
- gic = &gc->irq_contexts[j];
+ for (i -= 1; i >= 0; i--) {
+ irq = pci_irq_vector(pdev, i);
+ gic = xa_load(&gc->irq_contexts, i);
+ if (WARN_ON(!gic))
+ continue;

irq_update_affinity_hint(irq, NULL);
free_irq(irq, gic);
+ xa_erase(&gc->irq_contexts, i);
+ kfree(gic);
}

- kfree(gc->irq_contexts);
- gc->irq_contexts = NULL;
-free_irq_array:
- kfree(irqs);
-free_irq_vector:
- cpus_read_unlock();
- pci_free_irq_vectors(pdev);
+ kfree(start_irqs);
return err;
}

+static int mana_gd_setup_hwc_irqs(struct pci_dev *pdev)
+{
+ struct gdma_context *gc = pci_get_drvdata(pdev);
+ unsigned int max_irqs, min_irqs;
+ int nvec, err;
+
+ if (pci_msix_can_alloc_dyn(pdev)) {
+ max_irqs = 1;
+ min_irqs = 1;
+ } else {
+ /* Need 1 interrupt for HWC */
+ max_irqs = min(num_online_cpus(), MANA_MAX_NUM_QUEUES) + 1;
+ min_irqs = 2;
+ }
+
+ nvec = pci_alloc_irq_vectors(pdev, min_irqs, max_irqs, PCI_IRQ_MSIX);
+ if (nvec < 0)
+ return nvec;
+
+ err = mana_gd_setup_irqs(pdev, nvec);
+ if (err) {
+ pci_free_irq_vectors(pdev);
+ return err;
+ }
+
+ gc->num_msix_usable = nvec;
+ gc->max_num_msix = nvec;
+
+ return 0;
+}
+
+static int mana_gd_setup_remaining_irqs(struct pci_dev *pdev)
+{
+ struct gdma_context *gc = pci_get_drvdata(pdev);
+ struct msi_map irq_map;
+ int max_irqs, i, err;
+
+ if (!pci_msix_can_alloc_dyn(pdev))
+ /* remain irqs are already allocated with HWC IRQ */
+ return 0;
+
+ /* allocate only remaining IRQs*/
+ max_irqs = gc->num_msix_usable - 1;
+
+ for (i = 1; i <= max_irqs; i++) {
+ irq_map = pci_msix_alloc_irq_at(pdev, i, NULL);
+ if (!irq_map.virq) {
+ err = irq_map.index;
+ /* caller will handle cleaning up all allocated
+ * irqs, after HWC is destroyed
+ */
+ return err;
+ }
+ }
+
+ err = mana_gd_setup_dyn_irqs(pdev, max_irqs);
+ if (err)
+ return err;
+
+ gc->max_num_msix = gc->max_num_msix + max_irqs;
+
+ return 0;
+}
+
static void mana_gd_remove_irqs(struct pci_dev *pdev)
{
struct gdma_context *gc = pci_get_drvdata(pdev);
@@ -1495,19 +1629,21 @@ static void mana_gd_remove_irqs(struct pci_dev *pdev)
if (irq < 0)
continue;

- gic = &gc->irq_contexts[i];
+ gic = xa_load(&gc->irq_contexts, i);
+ if (WARN_ON(!gic))
+ continue;

/* Need to clear the hint before free_irq */
irq_update_affinity_hint(irq, NULL);
free_irq(irq, gic);
+ xa_erase(&gc->irq_contexts, i);
+ kfree(gic);
}

pci_free_irq_vectors(pdev);

gc->max_num_msix = 0;
gc->num_msix_usable = 0;
- kfree(gc->irq_contexts);
- gc->irq_contexts = NULL;
}

static int mana_gd_setup(struct pci_dev *pdev)
@@ -1522,9 +1658,10 @@ static int mana_gd_setup(struct pci_dev *pdev)
if (!gc->service_wq)
return -ENOMEM;

- err = mana_gd_setup_irqs(pdev);
+ err = mana_gd_setup_hwc_irqs(pdev);
if (err) {
- dev_err(gc->dev, "Failed to setup IRQs: %d\n", err);
+ dev_err(gc->dev, "Failed to setup IRQs for HWC creation: %d\n",
+ err);
goto free_workqueue;
}

@@ -1540,6 +1677,12 @@ static int mana_gd_setup(struct pci_dev *pdev)
if (err)
goto destroy_hwc;

+ err = mana_gd_setup_remaining_irqs(pdev);
+ if (err) {
+ dev_err(gc->dev, "Failed to setup remaining IRQs: %d", err);
+ goto destroy_hwc;
+ }
+
err = mana_gd_detect_devices(pdev);
if (err)
goto destroy_hwc;
@@ -1620,6 +1763,7 @@ static int mana_gd_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
gc->is_pf = mana_is_pf(pdev->device);
gc->bar0_va = bar0_va;
gc->dev = &pdev->dev;
+ xa_init(&gc->irq_contexts);

if (gc->is_pf)
gc->mana_pci_debugfs = debugfs_create_dir("0", mana_debugfs_root);
@@ -1654,6 +1798,7 @@ static int mana_gd_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
*/
debugfs_remove_recursive(gc->mana_pci_debugfs);
gc->mana_pci_debugfs = NULL;
+ xa_destroy(&gc->irq_contexts);
pci_iounmap(pdev, bar0_va);
free_gc:
pci_set_drvdata(pdev, NULL);
@@ -1679,6 +1824,8 @@ static void mana_gd_remove(struct pci_dev *pdev)

gc->mana_pci_debugfs = NULL;

+ xa_destroy(&gc->irq_contexts);
+
pci_iounmap(pdev, gc->bar0_va);

vfree(gc);
diff --git a/include/net/mana/gdma.h b/include/net/mana/gdma.h
index 3ce56a816425..87162ba96d91 100644
--- a/include/net/mana/gdma.h
+++ b/include/net/mana/gdma.h
@@ -388,7 +388,7 @@ struct gdma_context {
unsigned int max_num_queues;
unsigned int max_num_msix;
unsigned int num_msix_usable;
- struct gdma_irq_context *irq_contexts;
+ struct xarray irq_contexts;

/* L2 MTU */
u16 adapter_mtu;
@@ -578,12 +578,16 @@ enum {
/* Driver can handle holes (zeros) in the device list */
#define GDMA_DRV_CAP_FLAG_1_DEV_LIST_HOLES_SUP BIT(11)

+/* Driver supports dynamic MSI-X vector allocation */
+#define GDMA_DRV_CAP_FLAG_1_DYNAMIC_IRQ_ALLOC_SUPPORT BIT(13)
+
#define GDMA_DRV_CAP_FLAGS1 \
(GDMA_DRV_CAP_FLAG_1_EQ_SHARING_MULTI_VPORT | \
GDMA_DRV_CAP_FLAG_1_NAPI_WKDONE_FIX | \
GDMA_DRV_CAP_FLAG_1_HWC_TIMEOUT_RECONFIG | \
GDMA_DRV_CAP_FLAG_1_VARIABLE_INDIRECTION_TABLE_SUPPORT | \
- GDMA_DRV_CAP_FLAG_1_DEV_LIST_HOLES_SUP)
+ GDMA_DRV_CAP_FLAG_1_DEV_LIST_HOLES_SUP | \
+ GDMA_DRV_CAP_FLAG_1_DYNAMIC_IRQ_ALLOC_SUPPORT)

#define GDMA_DRV_CAP_FLAGS2 0

--
2.34.1