Re: [PATCH] pci: Added flag to pci_host_bridge to hint not to use acpi

[Keith Busch <keith.busch@intel.com>]

On Wed, Mar 23, 2016 at 04:01:58PM -0600, Jon Derrick wrote:
> This patch adds a hint, no_acpi, to the pci_host_bridge struct which
> informs the hotplug driver to not try and release the host bridge from
> acpi.
> 
> The VMD driver creates a root port which does not have an acpi entry.
> This patch will allow the hotplug driver to bypass acpi release when
> enumerating the VMD root port as a hotplug slot.

I want to add a little context to this for the motivation for this
implementation.

Currently we have to set kernel parameter "pcie_ports=native" for pciehp
to work on these domains since they are not known to ACPI. We don't want
to force a system wide PCIe parameter for something specific to a subset
of domains.

If the implementation here sounds reasonable, I suggest having a helper
API function in pci to check for the host bridge requested acpi disabled.

>  arch/x86/pci/vmd.c              | 4 ++++
>  drivers/pci/pcie/portdrv_acpi.c | 5 +++++
>  include/linux/pci.h             | 1 +
>  3 files changed, 10 insertions(+)
> 
> diff --git a/arch/x86/pci/vmd.c b/arch/x86/pci/vmd.c
> index 7792aba..a196be3 100644
> --- a/arch/x86/pci/vmd.c
> +++ b/arch/x86/pci/vmd.c
> @@ -531,6 +531,7 @@ static int vmd_find_free_domain(void)
>  static int vmd_enable_domain(struct vmd_dev *vmd)
>  {
>  	struct pci_sysdata *sd = &vmd->sysdata;
> +	struct pci_host_bridge *host_bridge;
>  	struct resource *res;
>  	u32 upper_bits;
>  	unsigned long flags;
> @@ -609,6 +610,9 @@ static int vmd_enable_domain(struct vmd_dev *vmd)
>  		return -ENODEV;
>  	}
>  
> +	host_bridge = to_pci_host_bridge(vmd->bus->bridge);
> +	host_bridge->no_acpi = true;
> +
>  	vmd_attach_resources(vmd);
>  	vmd_setup_dma_ops(vmd);
>  	dev_set_msi_domain(&vmd->bus->dev, vmd->irq_domain);
> diff --git a/drivers/pci/pcie/portdrv_acpi.c b/drivers/pci/pcie/portdrv_acpi.c
> index b4d2894..0e6fa69 100644
> --- a/drivers/pci/pcie/portdrv_acpi.c
> +++ b/drivers/pci/pcie/portdrv_acpi.c
> @@ -35,12 +35,17 @@
>  int pcie_port_acpi_setup(struct pci_dev *port, int *srv_mask)
>  {
>  	struct acpi_pci_root *root;
> +	struct pci_host_bridge *host_bridge;
>  	acpi_handle handle;
>  	u32 flags;
>  
>  	if (acpi_pci_disabled)
>  		return 0;
>  
> +	host_bridge = pci_find_host_bridge(port->bus);
> +	if (host_bridge && host_bridge->no_acpi)
> +		return 0;
> +
>  	handle = acpi_find_root_bridge_handle(port);
>  	if (!handle)
>  		return -EINVAL;
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 15f466e..a6958e9b 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -407,6 +407,7 @@ struct pci_host_bridge {
>  	void (*release_fn)(struct pci_host_bridge *);
>  	void *release_data;
>  	unsigned int ignore_reset_delay:1;	/* for entire hierarchy */
> +	unsigned int no_acpi:1;			/* bypasses acpi release */
>  	/* Resource alignment requirements */
>  	resource_size_t (*align_resource)(struct pci_dev *dev,
>  			const struct resource *res,
> -- 
> 1.8.3.1