Re: [RFC PATCH] PCI: Add "pci=reassign_all_bus" boot parameter

[Yao Hongbo <yaohongbo@linux.alibaba.com>]

Hi, Bjorn,
Gentel ping! Any comments on this patch?

I think this is useful to find whether there is a problem with
the PCI enumeration of the bios or the OS.

在 2021/12/30 下午5:30, Yao Hongbo 写道:
> PCI bridges may be misconfigured by te system BIOS, and then the OS
> scan the bridges that need to be reconfigured.
> However, the PCI bus topology configured by the bios may be wrong:
> 
> [   19.376273] pci 0000:40:00.0: bridge configuration invalid ([bus
> 00-00]), reconfiguring
> [   19.384443] pci_bus 0000:47: busn_res: can not insert [bus 47-46]
> under [bus 40-46] (conflicts with (null) [bus 40-46])
> 
> The primary bus number and subordinate bus number written by the bios
> were wrong, and the OS continues to add bridges on the wrong bus
> topology.
> 
> In order to avoid such problems, a kernel cmdline needs to be
> added to support the os to fully configure the pci bus.
> 
> Signed-off-by: Yao Hongbo <yaohongbo@linux.alibaba.com>
> ---
>  Documentation/admin-guide/kernel-parameters.txt | 1 +
>  drivers/acpi/pci_root.c                         | 3 +++
>  drivers/pci/pci.c                               | 5 +++++
>  include/linux/pci.h                             | 2 ++
>  4 files changed, 11 insertions(+)
> 
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 2fba824..c83a2e5 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -4084,6 +4084,7 @@
>  		nomio		[S390] Do not use MIO instructions.
>  		norid		[S390] ignore the RID field and force use of
>  				one PCI domain per PCI function
> +		reassign_all_bus	The OS fully configure the PCI bus.
>  
>  	pcie_aspm=	[PCIE] Forcibly enable or disable PCIe Active State Power
>  			Management.
> diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
> index ab2f7df..e21ac25 100644
> --- a/drivers/acpi/pci_root.c
> +++ b/drivers/acpi/pci_root.c
> @@ -592,6 +592,9 @@ static int acpi_pci_root_add(struct acpi_device *device,
>  	is_pcie = strcmp(acpi_device_hid(device), "PNP0A08") == 0;
>  	negotiate_os_control(root, &no_aspm, is_pcie);
>  
> +	if (pci_reassign_all_bus)
> +		pci_add_flags(PCI_REASSIGN_ALL_BUS);
> +
>  	/*
>  	 * TBD: Need PCI interface for enumeration/configuration of roots.
>  	 */
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index 3d2fb39..5746e88 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -142,6 +142,9 @@ bool pci_reset_supported(struct pci_dev *dev)
>  /* If set, the PCI config space of each device is printed during boot. */
>  bool pci_early_dump;
>  
> +/* If set, the pci will reassign resources*/
> +bool pci_reassign_all_bus;
> +
>  bool pci_ats_disabled(void)
>  {
>  	return pcie_ats_disabled;
> @@ -6846,6 +6849,8 @@ static int __init pci_setup(char *str)
>  				pci_add_flags(PCI_SCAN_ALL_PCIE_DEVS);
>  			} else if (!strncmp(str, "disable_acs_redir=", 18)) {
>  				disable_acs_redir_param = str + 18;
> +			} else if (!strncmp(str, "reassign_all_bus", 16)) {
> +				pci_reassign_all_bus = true;
>  			} else {
>  				pr_err("PCI: Unknown option `%s'\n", str);
>  			}
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 18a75c8e..ad0e3e9 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -2119,6 +2119,8 @@ int pcim_iomap_regions_request_all(struct pci_dev *pdev, int mask,
>  extern u8 pci_dfl_cache_line_size;
>  extern u8 pci_cache_line_size;
>  
> +extern bool pci_reassign_all_bus;
> +
>  /* Architecture-specific versions may override these (weak) */
>  void pcibios_disable_device(struct pci_dev *dev);
>  void pcibios_set_master(struct pci_dev *dev);