Re: [PATCH rc] PCI: Fix pci_enable_acs() support for the ACS quirks

[Bjorn Helgaas <helgaas@kernel.org>]

On Wed, Oct 16, 2024 at 08:52:33PM -0300, Jason Gunthorpe wrote:
> There are ACS quirks that hijack the normal ACS processing and deliver to
> to special quirk code. The enable path needs to call
> pci_dev_specific_enable_acs() and then pci_dev_specific_acs_enabled() will
> report the hidden ACS state controlled by the quirk.
> 
> The recent rework got this out of order and we should try to call
> pci_dev_specific_enable_acs() regardless of any actual ACS support in the
> device.
> 
> As before command line parameters that effect standard PCI ACS don't
> interact with the quirk versions, including the new config_acs= option.
> 
> Fixes: 47c8846a49ba ("PCI: Extend ACS configurability")
> Reported-by: Jiri Slaby <jirislaby@kernel.org>
> Closes: https://lore.kernel.org/all/e89107da-ac99-4d3a-9527-a4df9986e120@kernel.org
> Closes: https://bugzilla.suse.com/show_bug.cgi?id=1229019
> Tested-by: Steffen Dirkwinkel <me@steffen.cc>
> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

Applied to pci/for-linus for v6.12, thanks for the ping.

> ---
>  drivers/pci/pci.c | 14 +++++++++-----
>  1 file changed, 9 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index 7d85c04fbba2ae..225a6cd2e9ca3b 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -1067,8 +1067,15 @@ static void pci_std_enable_acs(struct pci_dev *dev, struct pci_acs *caps)
>  static void pci_enable_acs(struct pci_dev *dev)
>  {
>  	struct pci_acs caps;
> +	bool enable_acs = false;
>  	int pos;
>  
> +	/* If an iommu is present we start with kernel default caps */
> +	if (pci_acs_enable) {
> +		if (pci_dev_specific_enable_acs(dev))
> +			enable_acs = true;
> +	}
> +
>  	pos = dev->acs_cap;
>  	if (!pos)
>  		return;
> @@ -1077,11 +1084,8 @@ static void pci_enable_acs(struct pci_dev *dev)
>  	pci_read_config_word(dev, pos + PCI_ACS_CTRL, &caps.ctrl);
>  	caps.fw_ctrl = caps.ctrl;
>  
> -	/* If an iommu is present we start with kernel default caps */
> -	if (pci_acs_enable) {
> -		if (pci_dev_specific_enable_acs(dev))
> -			pci_std_enable_acs(dev, &caps);
> -	}
> +	if (enable_acs)
> +		pci_std_enable_acs(dev, &caps);
>  
>  	/*
>  	 * Always apply caps from the command line, even if there is no iommu.
> 
> base-commit: dc5006cfcf62bea88076a587344ba5e00e66d1c6
> -- 
> 2.46.2
>