Re: [PATCH v10 1/6] PCI: Validate ACS control bits against device-specific ACS capabilities

[sashiko-bot@kernel.org]

> The ACS control validation used the kernel's full set of ACS control bits,
> which allowed users to request ACS features that the device does not
> support. Because hardware silently ignores these unsupported bits, users
> have no indication that their config_acs= request was partially
> ineffective.
> 
> Validate the requested ACS control bits against dev->acs_capabilities so
> that only device-supported ACS controls are accepted. Mask the capability
> with PCI_ACS_BASIC_CTRL_MASK to select only the currently defined ACS
> control bits (0-6). Higher bits in the capability structure (e.g. the
> egress control vector size in bits 8-15) do not correspond to control bits
> in the ACS control register. Warn about any unsupported bits that are
> ignored.
> 
> __pci_config_acs() is also called from disable_acs_redir_param(), which
> passes a hardcoded acs_mask (PCI_ACS_RR | PCI_ACS_CR | PCI_ACS_EC) that
> does not need validation. Gate the new check on !acs_mask so it only
> fires for the config_acs_param path, which always invokes
> __pci_config_acs() with acs_mask == 0 and builds the actual mask from
> user input.
> 
> Also move the check after the device is matched, since the ctrl bits apply
> only to the matched device.
> 
> Signed-off-by: Wei Wang <wei.w.wang@hotmail.com>

Sashiko has reviewed this patch and found no issues. It looks great!

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