Re: [PATCH v7 2/6] Documentation/kernel-parameters: Add multi-device config_acs example

[Randy Dunlap <rdunlap@infradead.org>]

Hi,

On 5/6/26 7:10 AM, Wei Wang wrote:
> The config_acs parameter allows configuring ACS settings for multiple PCI
> devices by separating entries with semicolons. The current documentation
> only illustrates applying one configuration pattern to all devices, but
> does not show how to specify multiple devices with different ACS settings
> in a single parameter. Add an example demonstrating multi-device usage
> with distinct ACS configurations.
> 
> Some bootloaders interpret ';' as a command separator, which can cause
> the parameter to be split as multiple commands. Document that the entire
> parameter may need to be quoted to avoid bootloader parsing issues. This
> avoids confusing bootloader errors such as ‘can't find command <BDF>’
> when passing multiple device entries.
> 
> Signed-off-by: Wei Wang <wei.w.wang@hotmail.com>
> Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
> ---
>  Documentation/admin-guide/kernel-parameters.txt | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 170aae226e2e..0c159ab59e14 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -5277,15 +5277,20 @@ Kernel parameters
>  				  '1' – force enabled
>  				  'x' – unchanged
>  				For example,
> -				  pci=config_acs=10x@pci:0:0
> +				- pci=config_acs=10x@pci:0:0

Are these added hyphens/dashes helpful?
Are they needed for some reason?
I don't see any problem here without the leading '-'.
They (here and below) seem like they could add some confusion IMO.

>  				would configure all devices that support
>  				ACS to enable P2P Request Redirect, disable
>  				Translation Blocking, and leave Source
>  				Validation unchanged from whatever power-up
>  				or firmware set it to.
> -
>  				Note: this may remove isolation between devices
>  				and may put more devices in an IOMMU group.
> +				- 'pci=config_acs=10x@0000:04:00.0;1x101@0000:84:00.0'
> +				configures two devices with different ACS settings.
> +				Note: Some bootloaders interpret ';' as a command
> +				separator. If so, quote the entire parameter to
> +				ensure it is passed to the kernel unchanged.
> +
>  		force_floating	[S390] Force usage of floating interrupts.
>  		nomio		[S390] Do not use MIO instructions.
>  		norid		[S390] ignore the RID field and force use of

-- 
~Randy