linux-kernel - [PATCH v4 2/2] powerpc/pseries: Pass MSI affinity to irq_create

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Date:   Thu, 26 Nov 2020 09:28:52 +0100
From:   Laurent Vivier <lvivier@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     Paul Mackerras <paulus@...ba.org>, linux-pci@...r.kernel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-block@...r.kernel.org,
        "Michael S . Tsirkin" <mst@...hat.com>,
        Marc Zyngier <maz@...nel.org>, Christoph Hellwig <hch@....de>,
        Greg Kurz <groug@...d.org>, linuxppc-dev@...ts.ozlabs.org,
        Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Laurent Vivier <lvivier@...hat.com>
Subject: [PATCH v4 2/2] powerpc/pseries: Pass MSI affinity to irq_create_mapping()

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.

As the previous patch has added the affinity parameter to
irq_create_mapping() we can forward the affinity from rtas_setup_msi_irqs()
to irq_domain_alloc_descs().

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

Signed-off-by: Laurent Vivier <lvivier@...hat.com>
Reviewed-by: Greg Kurz <groug@...d.org>
Acked-by: Michael Ellerman <mpe@...erman.id.au>
---
 arch/powerpc/platforms/pseries/msi.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/platforms/pseries/msi.c b/arch/powerpc/platforms/pseries/msi.c
index 133f6adcb39c..b3ac2455faad 100644
--- a/arch/powerpc/platforms/pseries/msi.c
+++ b/arch/powerpc/platforms/pseries/msi.c
@@ -458,7 +458,8 @@ static int rtas_setup_msi_irqs(struct pci_dev *pdev, int nvec_in, int type)
 			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);
-- 
2.28.0