[RFC PATCH] xen: Introduce extra IRQ count domain creation parameter

["Teddy Astie" <teddy.astie@xxxxxxxxxx>]

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.astie@xxxxxxxxxx>
---
0 extra_irqs is meaningful, though I am not sure how to expose this
special case.

This of course wants libxl support next.
---
 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;
+        d->nr_pirqs = extra_irqs ? nr_static_irqs + extra_irqs : 
arch_hwdom_irqs(d);
+    }
     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;
+
     struct xen_arch_domainconfig arch;
 };
 
-- 
2.49.0



Teddy Astie | Vates XCP-ng Developer

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