linux-kernel - Re: [PATCH v2 2/2] powerpc/pseries: pass MSI affinity to irq_create

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Date:   Wed, 25 Nov 2020 13:51:45 +0100
From:   Greg Kurz <groug@...d.org>
To:     Laurent Vivier <lvivier@...hat.com>
CC:     <linux-kernel@...r.kernel.org>, <linux-block@...r.kernel.org>,
        "Paul Mackerras" <paulus@...ba.org>, <linux-pci@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Marc Zyngier <maz@...nel.org>, <linuxppc-dev@...ts.ozlabs.org>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        "Michael S . Tsirkin" <mst@...hat.com>,
        Christoph Hellwig <hch@....de>,
        Michael Ellerman <mpe@...erman.id.au>
Subject: Re: [PATCH v2 2/2] powerpc/pseries: pass MSI affinity to
 irq_create_mapping()

On Wed, 25 Nov 2020 12:16:57 +0100
Laurent Vivier <lvivier@...hat.com> wrote:

> 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.
> 

Since it is public, maybe add:

BugId: https://bugzilla.redhat.com/show_bug.cgi?id=1702939

?

> Signed-off-by: Laurent Vivier <lvivier@...hat.com>
> ---

Anyway,

Reviewed-by: Greg Kurz <groug@...d.org>

>  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);