Re: [PATCH v2 08/11] PCI: Clean up ATS error handling

[Joerg Roedel <jroedel@suse.de>]

On Mon, Jul 20, 2015 at 07:14:54PM -0500, Bjorn Helgaas wrote:
> There's no need to BUG() if we enable ATS when it's already enabled.  We
> don't need to BUG() when disabling ATS on a device that doesn't support ATS
> or if it's already disabled.  If ATS is enabled, certainly we found an ATS
> capability in the past, so it should still be there now.
> 
> Clean up these error paths.
> 
> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
> ---
>  drivers/pci/ats.c |   10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/pci/ats.c b/drivers/pci/ats.c
> index 0b5b0ed..67524a7 100644
> --- a/drivers/pci/ats.c
> +++ b/drivers/pci/ats.c
> @@ -44,11 +44,12 @@ int pci_enable_ats(struct pci_dev *dev, int ps)
>  	u16 ctrl;
>  	struct pci_dev *pdev;
>  
> -	BUG_ON(dev->ats_cap && dev->ats_enabled);
> -
>  	if (!dev->ats_cap)
>  		return -EINVAL;
>  
> +	if (pci_ats_enabled(dev))
> +		return -EINVAL;
> +

Better return -EBUSY here? It would be good to find out if we are trying
to enable ATS while it is already enabled. A WARN_ON around this would
also be good, so that we spot bugs in the iommu drivers early when they
use this interface.



	Joerg