On Fri, May 16, 2025 at 01:50:25PM +0000, Teddy Astie wrote:
> When doing PCI Passthrough with high-IRQ devices (e.g NVMe drives),
> the default limit may be unefficient as not all domains requires
> more IRQs.
>
> Introduce a new parameter to allow the toolstack to tune the IRQ
> count if more is required.
>
> Signed-off-by: Teddy Astie <teddy.as...@vates.tech>
> ---
> 0 extra_irqs is meaningful, though I am not sure how to expose this
> special case.
You could introduce a new CDF flag to signal the contents of
extra_irqs is valid, or maybe use the top bit of the `extra_irqs`
field to signal the value is set?
> This of course wants libxl support next.
It would be nice if this could come together in a patch series.
> ---
> xen/common/domain.c | 8 +++++---
> xen/include/public/domctl.h | 3 +++
> 2 files changed, 8 insertions(+), 3 deletions(-)
>
> diff --git a/xen/common/domain.c b/xen/common/domain.c
> index abf1969e60..5c628962fc 100644
> --- a/xen/common/domain.c
> +++ b/xen/common/domain.c
> @@ -912,10 +912,12 @@ struct domain *domain_create(domid_t domid,
>
> #ifdef CONFIG_HAS_PIRQ
> if ( !is_hardware_domain(d) )
> - d->nr_pirqs = nr_static_irqs + extra_domU_irqs;
> + d->nr_pirqs = nr_static_irqs + config->extra_irqs ?: extra_domU_irqs;
> else
> - d->nr_pirqs = extra_hwdom_irqs ? nr_static_irqs + extra_hwdom_irqs
> - : arch_hwdom_irqs(d);
> + {
> + unsigned int extra_irqs = config->extra_irqs ?: extra_hwdom_irqs;
Newline.
> + d->nr_pirqs = extra_irqs ? nr_static_irqs + extra_irqs :
> arch_hwdom_irqs(d);
I think the above line is > 80 characters?
> + }
> d->nr_pirqs = min(d->nr_pirqs, nr_irqs);
>
> radix_tree_init(&d->pirq_tree);
> diff --git a/xen/include/public/domctl.h b/xen/include/public/domctl.h
> index 5b2063eed9..e4bb366c78 100644
> --- a/xen/include/public/domctl.h
> +++ b/xen/include/public/domctl.h
> @@ -121,6 +121,9 @@ struct xen_domctl_createdomain {
> /* CPU pool to use; specify 0 or a specific existing pool */
> uint32_t cpupool_id;
>
> + /* Additional IRQ for this guest. 0 to use Xen default value. */
> + uint32_t extra_irqs;
I think you need a domctl version bump, as the last one was done for
4.19.
Regards, Roger.
