[PATCH v8 2/6] Documentation/kernel-parameters: Add multi-device config_acs example

[Wei Wang]

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@xxxxxxxxxxx>
Reviewed-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
---
 Documentation/admin-guide/kernel-parameters.txt | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 6f0910abdd25..91d2f3fbf8e7 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -5281,6 +5281,13 @@ Kernel parameters
 
 				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
-- 
2.51.0