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SubjectRe: [PATCH 13/16] irq: add support for allocating (and affinitizing) sets of IRQs
On Tue, Oct 30, 2018 at 12:32:49PM -0600, Jens Axboe wrote:
> A driver may have a need to allocate multiple sets of MSI/MSI-X
> interrupts, and have them appropriately affinitized. Add support for
> defining a number of sets in the irq_affinity structure, of varying
> sizes, and get each set affinitized correctly across the machine.
>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: linux-kernel@vger.kernel.org
> Reviewed-by: Hannes Reinecke <hare@suse.com>
> Reviewed-by: Ming Lei <ming.lei@redhat.com>
> Signed-off-by: Jens Axboe <axboe@kernel.dk>
> ---
> drivers/pci/msi.c | 14 ++++++++++++++
> include/linux/interrupt.h | 4 ++++
> kernel/irq/affinity.c | 40 ++++++++++++++++++++++++++++++---------
> 3 files changed, 49 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
> index af24ed50a245..e6c6e10b9ceb 100644
> --- a/drivers/pci/msi.c
> +++ b/drivers/pci/msi.c
> @@ -1036,6 +1036,13 @@ static int __pci_enable_msi_range(struct pci_dev *dev, int minvec, int maxvec,
> if (maxvec < minvec)
> return -ERANGE;
>
> + /*
> + * If the caller is passing in sets, we can't support a range of
> + * vectors. The caller needs to handle that.
> + */
> + if (affd->nr_sets && minvec != maxvec)
> + return -EINVAL;
> +
> if (WARN_ON_ONCE(dev->msi_enabled))
> return -EINVAL;
>
> @@ -1087,6 +1094,13 @@ static int __pci_enable_msix_range(struct pci_dev *dev,
> if (maxvec < minvec)
> return -ERANGE;
>
> + /*
> + * If the caller is passing in sets, we can't support a range of
> + * supported vectors. The caller needs to handle that.
> + */
> + if (affd->nr_sets && minvec != maxvec)
> + return -EINVAL;
> +
> if (WARN_ON_ONCE(dev->msix_enabled))
> return -EINVAL;
>
> diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
> index 1d6711c28271..ca397ff40836 100644
> --- a/include/linux/interrupt.h
> +++ b/include/linux/interrupt.h
> @@ -247,10 +247,14 @@ struct irq_affinity_notify {
> * the MSI(-X) vector space
> * @post_vectors: Don't apply affinity to @post_vectors at end of
> * the MSI(-X) vector space
> + * @nr_sets: Length of passed in *sets array
> + * @sets: Number of affinitized sets
> */
> struct irq_affinity {
> int pre_vectors;
> int post_vectors;
> + int nr_sets;
> + int *sets;
> };
>
> #if defined(CONFIG_SMP)
> diff --git a/kernel/irq/affinity.c b/kernel/irq/affinity.c
> index f4f29b9d90ee..2046a0f0f0f1 100644
> --- a/kernel/irq/affinity.c
> +++ b/kernel/irq/affinity.c
> @@ -180,6 +180,7 @@ irq_create_affinity_masks(int nvecs, const struct irq_affinity *affd)
> int curvec, usedvecs;
> cpumask_var_t nmsk, npresmsk, *node_to_cpumask;
> struct cpumask *masks = NULL;
> + int i, nr_sets;
>
> /*
> * If there aren't any vectors left after applying the pre/post
> @@ -210,10 +211,23 @@ irq_create_affinity_masks(int nvecs, const struct irq_affinity *affd)
> get_online_cpus();
> build_node_to_cpumask(node_to_cpumask);
>
> - /* Spread on present CPUs starting from affd->pre_vectors */
> - usedvecs = irq_build_affinity_masks(affd, curvec, affvecs,
> - node_to_cpumask, cpu_present_mask,
> - nmsk, masks);
> + /*
> + * Spread on present CPUs starting from affd->pre_vectors. If we
> + * have multiple sets, build each sets affinity mask separately.
> + */
> + nr_sets = affd->nr_sets;
> + if (!nr_sets)
> + nr_sets = 1;
> +
> + for (i = 0, usedvecs = 0; i < nr_sets; i++) {
> + int this_vecs = affd->sets ? affd->sets[i] : affvecs;
> + int nr;
> +
> + nr = irq_build_affinity_masks(affd, curvec, this_vecs,
> + node_to_cpumask, cpu_present_mask,
> + nmsk, masks + usedvecs);

The last parameter of the above function should have been 'masks',
because irq_build_affinity_masks() always treats 'masks' as the base
address of the array.

> + usedvecs += nr;
> + }

Thinking of further, one big problem in this patch is that each set of
IRQs should have been spread on all possible CPUs, which is done via
2-stages spread now.

However, this patch only spreads each set of IRQs on present CPUs, this
way may not work in case of physical CPU hotplug.

Thanks,
Ming

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