linux-kernel - Re: [PATCH] PCI: MSI: Only use the generic MSI layer when domain is hierarchical

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Date:	Thu, 3 Dec 2015 18:27:59 -0600
From:	Bjorn Helgaas <helgaas@...nel.org>
To:	Phil Edworthy <phil.edworthy@...esas.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Jiang Liu <jiang.liu@...ux.intel.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Wolfram Sang <wsa@...-dreams.de>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>
Subject: Re: [PATCH] PCI: MSI: Only use the generic MSI layer when domain is
 hierarchical

On Mon, Nov 30, 2015 at 10:25:34AM +0000, Phil Edworthy wrote:
> Cc'd linux-pci ml
> 
> On 23 November 2015 14:27, Marc Zyngier wrote:
> 
> Since d8a1cb757550 ("PCI/MSI: Let pci_msi_get_domain use struct
> device::msi_domain"), we use the MSI domain associated to the PCI device.
> 
> But finding a MSI domain doesn't mean that the domain is implemented
> using the generic MSI domain API, and a number of MSI controllers
> are still using the arch_setup_msi_irq/arch_teardown_msi_irqs.
> 
> In order to avoid a firework on these systems, check that the domain
> we just obtained is hierarchical. If not, don't use the generic MSI
> stuff and stick with the old one. Not pretty, but reliable.
> 
> Another insentive to rework those drivers and phase out this API.
> 
> Reported-by: Phil Edworthy <phil.edworthy@...esas.com>
> Tested-by: Phil Edworthy <phil.edworthy@...esas.com>
> Signed-off-by: Marc Zyngier <marc.zyngier@....com>

Thanks, I applied this with Thomas' ack to pci/msi for v4.5.

It looks like d8a1cb757550 appeared in v4.3.  Is this a fix for that
commit?  Does this need to be backported via a stable tag?

> ---
>  drivers/pci/msi.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
> index 53e4632..7eaa4c8 100644
> --- a/drivers/pci/msi.c
> +++ b/drivers/pci/msi.c
> @@ -54,7 +54,7 @@ static int pci_msi_setup_msi_irqs(struct pci_dev *dev, int nvec, int type)
>  	struct irq_domain *domain;
>  
>  	domain = pci_msi_get_domain(dev);
> -	if (domain)
> +	if (domain && irq_domain_is_hierarchy(domain))
>  		return pci_msi_domain_alloc_irqs(domain, dev, nvec, type);
>  
>  	return arch_setup_msi_irqs(dev, nvec, type);
> @@ -65,7 +65,7 @@ static void pci_msi_teardown_msi_irqs(struct pci_dev *dev)
>  	struct irq_domain *domain;
>  
>  	domain = pci_msi_get_domain(dev);
> -	if (domain)
> +	if (domain && irq_domain_is_hierarchy(domain))
>  		pci_msi_domain_free_irqs(domain, dev);
>  	else
>  		arch_teardown_msi_irqs(dev);
> -- 
> 2.1.4
> 
> --
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