linux-kernel - Re: [PATCH] genirq/msi: Do not use pci_msi_[un]mask

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Message-ID: <alpine.DEB.2.11.1510151040320.3960@nanos>
Date:	Thu, 15 Oct 2015 10:40:41 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Marc Zyngier <marc.zyngier@....com>
cc:	Jiang Liu <jiang.liu@...ux.intel.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] genirq/msi: Do not use pci_msi_[un]mask_irq as default
 methods

On Tue, 13 Oct 2015, Marc Zyngier wrote:

> When we create a generic MSI domain, that MSI_FLAG_USE_DEF_CHIP_OPS
> is set, and that any of .mask or .unmask are NULL in the irq_chip
> structure, we set them to pci_msi_[un]mask_irq.
> 
> This is a bad idea for at least two reasons:
> - PCI_MSI might not be selected, kernel fails to build (yes, this is
>   legitimate, at least on arm64!)
> - This may not be a PCI/MSI domain at all (platform MSI, for example)
> 
> Either way, this looks wrong. Move the overriding of mask/unmask to
> the PCI counterpart, and panic is any of these two methods is not
> set in the core code (they really should be present).
> 
> Signed-off-by: Marc Zyngier <marc.zyngier@....com>

Reviewed-by: Thomas Gleixner <tglx@...utronix.de>

> ---
>  drivers/pci/msi.c | 4 ++++
>  kernel/irq/msi.c  | 6 +-----
>  2 files changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
> index d449714..4a7da3c 100644
> --- a/drivers/pci/msi.c
> +++ b/drivers/pci/msi.c
> @@ -1243,6 +1243,10 @@ static void pci_msi_domain_update_chip_ops(struct msi_domain_info *info)
>  	BUG_ON(!chip);
>  	if (!chip->irq_write_msi_msg)
>  		chip->irq_write_msi_msg = pci_msi_domain_write_msg;
> +	if (!chip->irq_mask)
> +		chip->irq_mask = pci_msi_mask_irq;
> +	if (!chip->irq_unmask)
> +		chip->irq_unmask = pci_msi_unmask_irq;
>  }
>  
>  /**
> diff --git a/kernel/irq/msi.c b/kernel/irq/msi.c
> index 7e6512b..be9149f 100644
> --- a/kernel/irq/msi.c
> +++ b/kernel/irq/msi.c
> @@ -228,11 +228,7 @@ static void msi_domain_update_chip_ops(struct msi_domain_info *info)
>  {
>  	struct irq_chip *chip = info->chip;
>  
> -	BUG_ON(!chip);
> -	if (!chip->irq_mask)
> -		chip->irq_mask = pci_msi_mask_irq;
> -	if (!chip->irq_unmask)
> -		chip->irq_unmask = pci_msi_unmask_irq;
> +	BUG_ON(!chip || !chip->irq_mask || !chip->irq_unmask);
>  	if (!chip->irq_set_affinity)
>  		chip->irq_set_affinity = msi_domain_set_affinity;
>  }
> -- 
> 2.1.4
> 
> 
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