linux-kernel - [PATCH 5.4 29/54] powerpc/pseries: Pass MSI affinity to irq_create

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Date:   Thu, 10 Dec 2020 15:27:06 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Laurent Vivier <lvivier@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Greg Kurz <groug@...d.org>,
        Michael Ellerman <mpe@...erman.id.au>
Subject: [PATCH 5.4 29/54] powerpc/pseries: Pass MSI affinity to irq_create_mapping()

From: Laurent Vivier <lvivier@...hat.com>

commit 9ea69a55b3b9a71cded9726af591949c1138f235 upstream.

With virtio multiqueue, normally each queue IRQ is mapped to a CPU.

Commit 0d9f0a52c8b9f ("virtio_scsi: use virtio IRQ affinity") exposed
an existing shortcoming of the arch code by moving virtio_scsi to
the automatic IRQ affinity assignment.

The affinity is correctly computed in msi_desc but this is not applied
to the system IRQs.

It appears the affinity is correctly passed to rtas_setup_msi_irqs() but
lost at this point and never passed to irq_domain_alloc_descs()
(see commit 06ee6d571f0e ("genirq: Add affinity hint to irq allocation"))
because irq_create_mapping() doesn't take an affinity parameter.

Use the new irq_create_mapping_affinity() function, which allows to forward
the affinity setting from rtas_setup_msi_irqs() to irq_domain_alloc_descs().

With this change, the virtqueues are correctly dispatched between the CPUs
on pseries.

Fixes: e75eafb9b039 ("genirq/msi: Switch to new irq spreading infrastructure")
Signed-off-by: Laurent Vivier <lvivier@...hat.com>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Reviewed-by: Greg Kurz <groug@...d.org>
Acked-by: Michael Ellerman <mpe@...erman.id.au>
Cc: stable@...r.kernel.org
Link: https://lore.kernel.org/r/20201126082852.1178497-3-lvivier@redhat.com
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/powerpc/platforms/pseries/msi.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/arch/powerpc/platforms/pseries/msi.c
+++ b/arch/powerpc/platforms/pseries/msi.c
@@ -458,7 +458,8 @@ again:
 			return hwirq;
 		}

-		virq = irq_create_mapping(NULL, hwirq);
+		virq = irq_create_mapping_affinity(NULL, hwirq,
+						   entry->affinity);

 		if (!virq) {
 			pr_debug("rtas_msi: Failed mapping hwirq %d\n", hwirq);