Hi Mykola,
On 03/09/2025 03:55, Mykola Kvach wrote:
From: Mykola Kvach <mykola_kv...@epam.com>
Use GIC_PRI_IPI priority for SGI interrupts instead of the generic
GIC_PRI_IRQ priority in setup_irq().
This change ensures that SGIs get the correct priority level when
being set up for Xen's use, maintaining proper interrupt precedence
in the system.
The priority assignment now follows ARM GIC best practices:
- SGIs (0-15): GIC_PRI_IPI (higher priority)
- PPIs/SPIs (16+): GIC_PRI_IRQ (standard priority)
Please provide a reference to the spec. But I don't follow why we should
follow exactly what the spec suggest. This is up to us to decide what we
want. Otherwise what's the point of having more than two priorities?
Signed-off-by: Mykola Kvach <mykola_kv...@epam.com>
---
xen/arch/arm/irq.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/xen/arch/arm/irq.c b/xen/arch/arm/irq.c
index 02ca82c089..17c7ac92b5 100644
--- a/xen/arch/arm/irq.c
+++ b/xen/arch/arm/irq.c
@@ -397,7 +397,13 @@ int setup_irq(unsigned int irq, unsigned int irqflags,
struct irqaction *new)
AFAIK, we are not using setup_irq() to handle SGIs because they are all
static and always enabled. Are you planning to handle dynamic SGIs? If
yes, then can you provide more details?
/* First time the IRQ is setup */
if ( disabled )
{
- gic_route_irq_to_xen(desc, GIC_PRI_IRQ);
+ unsigned int prio = GIC_PRI_IRQ;
+
+ /* Use appropriate priority based on interrupt type */
+ if (desc->irq < NR_GIC_SGI)
+ prio = GIC_PRI_IPI;
I am a bit split with this change. I feel static SGI (e.g. EVENT_CHECK,
CALL_FUNCTION) should have higher priority to the dynamic SGIs because
they are critical for Xen.
Before making my mind, I would like to understand a bit more the use case.
Cheers,
--
Julien Grall
