netdev - Re: [PATCH net 1/1] nfp: correct number of MSI vectors requests returned

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Message-ID: <20230316142512.4c9a9ff4@kernel.org>
Date:   Thu, 16 Mar 2023 14:25:12 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Louis Peens <louis.peens@...igine.com>,
        Thomas Gleixner <tglx@...utronix.de>
Cc:     David Miller <davem@...emloft.net>,
        Paolo Abeni <pabeni@...hat.com>,
        Simon Horman <simon.horman@...igine.com>,
        netdev@...r.kernel.org, stable@...r.kernel.org,
        oss-drivers@...igine.com, Jason Gunthorpe <jgg@...dia.com>
Subject: Re: [PATCH net 1/1] nfp: correct number of MSI vectors requests
 returned

On Wed, 15 Mar 2023 14:17:33 +0200 Louis Peens wrote:
> From: Xiaoyu Li <xiaoyu.li@...igine.com>
> 
> Before the referenced commit, when we requested a
> certain number of interrupts, if we could not meet
> the requirements, the number of interrupts supported
> by the hardware would be returned. But after the
> referenced commit, if the hardware failed to meet
> the requirements, the error of invalid argument
> would be directly returned, which caused a regression
> in the nfp driver preventing probing to complete.
> 
> Fixes: bab65e48cb06 ("PCI/MSI: Sanitize MSI-X checks")
> Cc: stable@...r.kernel.org
> Signed-off-by: Xiaoyu Li <xiaoyu.li@...igine.com>

Thomas, is this an expected side effect?

The commit message of bab65e48cb06 ("PCI/MSI: Sanitize MSI-X checks")
makes it sound like only a harmless refactoring was intended.

> diff --git a/drivers/net/ethernet/netronome/nfp/nfp_net_common.c b/drivers/net/ethernet/netronome/nfp/nfp_net_common.c
> index 62f0bf91d1e1..0e4cab38f075 100644
> --- a/drivers/net/ethernet/netronome/nfp/nfp_net_common.c
> +++ b/drivers/net/ethernet/netronome/nfp/nfp_net_common.c
> @@ -370,6 +370,12 @@ nfp_net_irqs_alloc(struct pci_dev *pdev, struct msix_entry *irq_entries,
>  {
>  	unsigned int i;
>  	int got_irqs;
> +	int max_irqs;
> +
> +	max_irqs = pci_msix_vec_count(pdev);
> +	if (max_irqs < 0)
> +		return max_irqs;
> +	wanted_irqs = min_t(unsigned int, max_irqs, wanted_irqs);
>  
>  	for (i = 0; i < wanted_irqs; i++)
>  		irq_entries[i].entry = i;