Re: [PATCH v4 5/5] net: mana: Allocate MSI-X vectors dynamically

[Simon Horman <horms@kernel.org>]

On Tue, May 27, 2025 at 08:59:03AM -0700, Shradha Gupta wrote:
> 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>

...

> +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;
> +
> +	cpus_read_lock();
> +
> +	irqs = kmalloc_array(nvec, sizeof(int), GFP_KERNEL);
> +	if (!irqs) {
>  		err = -ENOMEM;
> -		goto free_irq_array;
> +		goto free_irq_vector;
>  	}
>  
>  	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 +1498,128 @@ 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;

Jumping to free_current_gic will free start_irqs.
However, start_irqs isn't initialised until a few lines below.

Flagged by Smatch.

> +
> +		xa_store(&gc->irq_contexts, i, gic, GFP_KERNEL);
>  	}
>  
> -	err = irq_setup(irqs, nvec - start_irq_index, gc->numa_node, false);
> +	/* 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.
> +	 */
> +	start_irqs = irqs;
> +	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)
>  		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);
> +	kfree(start_irqs);
>  free_irq_vector:
>  	cpus_read_unlock();
> -	pci_free_irq_vectors(pdev);
>  	return err;
>  }

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