linux-kernel - Re: [PATCH v3 2/2] powerpc/pseries: pass MSI affinity to irq_create

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Message-ID: <87zh34yf7a.fsf@mpe.ellerman.id.au>
Date:   Thu, 26 Nov 2020 14:22:49 +1100
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Laurent Vivier <lvivier@...hat.com>, linux-kernel@...r.kernel.org
Cc:     linux-pci@...r.kernel.org, Christoph Hellwig <hch@....de>,
        Paul Mackerras <paulus@...ba.org>, Greg Kurz <groug@...d.org>,
        linuxppc-dev@...ts.ozlabs.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        linux-block@...r.kernel.org,
        "Michael S . Tsirkin" <mst@...hat.com>,
        Marc Zyngier <maz@...nel.org>,
        Laurent Vivier <lvivier@...hat.com>
Subject: Re: [PATCH v3 2/2] powerpc/pseries: pass MSI affinity to irq_create_mapping()

Laurent Vivier <lvivier@...hat.com> writes:
> With virtio multiqueue, normally each queue IRQ is mapped to a CPU.
>
> But since commit 0d9f0a52c8b9f ("virtio_scsi: use virtio IRQ affinity")
> this is broken on pseries.
>
> 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.
>
> BugId: https://bugzilla.redhat.com/show_bug.cgi?id=1702939
> Signed-off-by: Laurent Vivier <lvivier@...hat.com>
> Reviewed-by: Greg Kurz <groug@...d.org>
> ---
>  arch/powerpc/platforms/pseries/msi.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)

Acked-by: Michael Ellerman <mpe@...erman.id.au>

cheers

> 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