Re: [PATCH v2 1/6] blk-mq: introduce blk_mq_hctx_map_queues

[Bjorn Helgaas <helgaas@kernel.org>]

On Mon, Nov 11, 2024 at 07:02:09PM +0100, Daniel Wagner wrote:
> blk_mq_pci_map_queues and blk_mq_virtio_map_queues will create a CPU to
> hardware queue mapping based on affinity information. These two function
> share common code and only differ on how the affinity information is
> retrieved. Also, those functions are located in the block subsystem
> where it doesn't really fit in. They are virtio and pci subsystem
> specific.
> 
> Introduce a new callback in struct bus_type to get the affinity mask.
> The callbacks can then be populated by the subsystem directly.
> 
> All but one driver use the subsystem default affinity masks. hisi_sas v2
> depends on a driver specific mapping, thus use the optional argument
> get_queue_affinity to retrieve the mapping.
> 
> Original-by : Ming Lei <ming.lei@redhat.com>
> Signed-off-by: Daniel Wagner <wagi@kernel.org>
> ---
>  block/blk-mq-cpumap.c      | 40 ++++++++++++++++++++++++++++++++++++++++
>  drivers/pci/pci-driver.c   | 16 ++++++++++++++++
>  drivers/virtio/virtio.c    | 12 ++++++++++++
>  include/linux/blk-mq.h     |  5 +++++
>  include/linux/device/bus.h |  3 +++
>  5 files changed, 76 insertions(+)
> 
> diff --git a/block/blk-mq-cpumap.c b/block/blk-mq-cpumap.c
> index 9638b25fd52124f0173e968ebdca5f1fe0b42ad9..4dd703f5ee647fd1ba0b14ca11ddfdefa98a9a25 100644
> --- a/block/blk-mq-cpumap.c
> +++ b/block/blk-mq-cpumap.c
> @@ -54,3 +54,43 @@ int blk_mq_hw_queue_to_node(struct blk_mq_queue_map *qmap, unsigned int index)
>  
>  	return NUMA_NO_NODE;
>  }
> +
> +/**
> + * blk_mq_hctx_map_queues - Create CPU to hardware queue mapping
> + * @qmap:	CPU to hardware queue map.
> + * @dev:	The device to map queues.
> + * @offset:	Queue offset to use for the device.
> + * @get_irq_affinity:	Optional callback to retrieve queue affinity.
> + *
> + * Create a CPU to hardware queue mapping in @qmap. For each queue
> + * @get_queue_affinity will be called. If @get_queue_affinity is not
> + * provided, then the bus_type irq_get_affinity callback will be
> + * used to retrieve the affinity.
> + */
> +void blk_mq_hctx_map_queues(struct blk_mq_queue_map *qmap,
> +			    struct device *dev, unsigned int offset,
> +			    get_queue_affinity_fn *get_irq_affinity)
> +{
> +	const struct cpumask *mask = NULL;
> +	unsigned int queue, cpu;
> +
> +	for (queue = 0; queue < qmap->nr_queues; queue++) {
> +		if (get_irq_affinity)
> +			mask = get_irq_affinity(dev, queue + offset);
> +		else if (dev->bus->irq_get_affinity)
> +			mask = dev->bus->irq_get_affinity(dev, queue + offset);
> +
> +		if (!mask)
> +			goto fallback;
> +
> +		for_each_cpu(cpu, mask)
> +			qmap->mq_map[cpu] = qmap->queue_offset + queue;
> +	}
> +
> +	return;
> +
> +fallback:
> +	WARN_ON_ONCE(qmap->nr_queues > 1);
> +	blk_mq_clear_mq_map(qmap);
> +}
> +EXPORT_SYMBOL_GPL(blk_mq_hctx_map_queues);
> diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
> index 35270172c833186995aebdda6f95ab3ffd7c67a0..59e5f430a380285162a87bd1a9b392bba8066450 100644
> --- a/drivers/pci/pci-driver.c
> +++ b/drivers/pci/pci-driver.c
> @@ -1670,6 +1670,21 @@ static void pci_dma_cleanup(struct device *dev)
>  		iommu_device_unuse_default_domain(dev);
>  }
>  
> +/**
> + * pci_device_irq_get_affinity - get affinity mask queue mapping for PCI device
> + * @dev: ptr to dev structure
> + * @irq_vec: interrupt vector number
> + *
> + * This function returns for a queue the affinity mask for a PCI device.

From the PCI core perspective, this is only the *IRQ* affinity mask.
The queue connection is not relevant here and probably confusing.

  ... - get IRQ affinity mask for device

  Return the CPU affinity mask for @dev and @irq_vec.

With the above changes,

Acked-by: Bjorn Helgaas <bhelgaas@google.com>

> + */
> +static const struct cpumask *pci_device_irq_get_affinity(struct device *dev,
> +					unsigned int irq_vec)
> +{
> +	struct pci_dev *pdev = to_pci_dev(dev);
> +
> +	return pci_irq_get_affinity(pdev, irq_vec);
> +}
> +
>  const struct bus_type pci_bus_type = {
>  	.name		= "pci",
>  	.match		= pci_bus_match,
> @@ -1677,6 +1692,7 @@ const struct bus_type pci_bus_type = {
>  	.probe		= pci_device_probe,
>  	.remove		= pci_device_remove,
>  	.shutdown	= pci_device_shutdown,
> +	.irq_get_affinity = pci_device_irq_get_affinity,
>  	.dev_groups	= pci_dev_groups,
>  	.bus_groups	= pci_bus_groups,
>  	.drv_groups	= pci_drv_groups,
> diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
> index b9095751e43bb7db5fc991b0cc0979d2e86f7b9b..86390db7e74befa17c9fa146ab6b454bbae3b7f5 100644
> --- a/drivers/virtio/virtio.c
> +++ b/drivers/virtio/virtio.c
> @@ -377,6 +377,17 @@ static void virtio_dev_remove(struct device *_d)
>  	of_node_put(dev->dev.of_node);
>  }
>  
> +static const struct cpumask *virtio_irq_get_affinity(struct device *_d,
> +						     unsigned int irq_veq)
> +{
> +	struct virtio_device *dev = dev_to_virtio(_d);
> +
> +	if (!dev->config->get_vq_affinity)
> +		return NULL;
> +
> +	return dev->config->get_vq_affinity(dev, irq_veq);
> +}
> +
>  static const struct bus_type virtio_bus = {
>  	.name  = "virtio",
>  	.match = virtio_dev_match,
> @@ -384,6 +395,7 @@ static const struct bus_type virtio_bus = {
>  	.uevent = virtio_uevent,
>  	.probe = virtio_dev_probe,
>  	.remove = virtio_dev_remove,
> +	.irq_get_affinity = virtio_irq_get_affinity,
>  };
>  
>  int __register_virtio_driver(struct virtio_driver *driver, struct module *owner)
> diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
> index 2035fad3131fb60781957095ce8a3a941dd104be..6b40af77bf44afa7112d274b731b591f2a67d68c 100644
> --- a/include/linux/blk-mq.h
> +++ b/include/linux/blk-mq.h
> @@ -922,7 +922,12 @@ int blk_mq_freeze_queue_wait_timeout(struct request_queue *q,
>  void blk_mq_unfreeze_queue_non_owner(struct request_queue *q);
>  void blk_freeze_queue_start_non_owner(struct request_queue *q);
>  
> +typedef const struct cpumask *(get_queue_affinity_fn)(struct device *dev,
> +						      unsigned int queue);
>  void blk_mq_map_queues(struct blk_mq_queue_map *qmap);
> +void blk_mq_hctx_map_queues(struct blk_mq_queue_map *qmap,
> +			    struct device *dev, unsigned int offset,
> +			    get_queue_affinity_fn *get_queue_affinity);
>  void blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set, int nr_hw_queues);
>  
>  void blk_mq_quiesce_queue_nowait(struct request_queue *q);
> diff --git a/include/linux/device/bus.h b/include/linux/device/bus.h
> index cdc4757217f9bb4b36b5c3b8a48bab45737e44c5..b18658bce2c3819fc1cbeb38fb98391d56ec3317 100644
> --- a/include/linux/device/bus.h
> +++ b/include/linux/device/bus.h
> @@ -48,6 +48,7 @@ struct fwnode_handle;
>   *		will never get called until they do.
>   * @remove:	Called when a device removed from this bus.
>   * @shutdown:	Called at shut-down time to quiesce the device.
> + * @irq_get_affinity:	Get IRQ affinity mask for the device on this bus.
>   *
>   * @online:	Called to put the device back online (after offlining it).
>   * @offline:	Called to put the device offline for hot-removal. May fail.
> @@ -87,6 +88,8 @@ struct bus_type {
>  	void (*sync_state)(struct device *dev);
>  	void (*remove)(struct device *dev);
>  	void (*shutdown)(struct device *dev);
> +	const struct cpumask *(*irq_get_affinity)(struct device *dev,
> +			unsigned int irq_vec);
>  
>  	int (*online)(struct device *dev);
>  	int (*offline)(struct device *dev);
> 
> -- 
> 2.47.0
>