linux-kernel - Re: [PATCH 2/2] PCI, ACPI, x86: update MMCFG information when hot-plugging PCI host bridges

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Date:	Mon, 09 Apr 2012 20:43:32 +0900
From:	Kenji Kaneshige <kaneshige.kenji@...fujitsu.com>
To:	Jiang Liu <liuj97@...il.com>
CC:	Taku Izumi <izumi.taku@...fujitsu.com>,
	Yinghai Lu <yinghai@...nel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Jiang Liu <jiang.liu@...wei.com>,
	Keping Chen <chenkeping@...wei.com>,
	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org
Subject: Re: [PATCH 2/2] PCI, ACPI, x86: update MMCFG information when hot-plugging
 PCI host bridges

Your patch looks good to me.

I have some comments.

(2012/04/09 2:12), Jiang Liu wrote:
> This patch enhances pci_root driver to update MMCFG information when
> hot-plugging PCI root bridges on x86 platforms.
>

Do you have the patch that can be applied to Bjorn's pci tree?

<snip.>

> +int arch_acpi_pci_root_add(struct acpi_pci_root *root)
> +{
> +	int result = 0;
> +	acpi_status status;
> +	unsigned long long base_addr;
> +	struct pci_mmcfg_region *cfg;
> +
> +	/*
> +	 * Try to insert MMCFG information for host bridges with _CBA method
> +	 */
> +	status = acpi_evaluate_integer(root->device->handle, METHOD_NAME__CBA,
> +				       NULL,&base_addr);
> +	if (ACPI_SUCCESS(status)) {
> +		result = pci_mmconfig_insert(root->segment,
> +					     root->secondary.start,
> +					     root->secondary.end,
> +					     base_addr);
> +		/*
> +		 * MMCFG information for hot-pluggable host bridges may have
> +		 * already been added by __pci_mmcfg_init();
> +		 */
> +		if (result == -EEXIST)
> +			result = 0;

Just for confirmation.
>From my interpretation of PCI firmware spec, MCFG doesn't have any entry
for hot-pluggable hostbridge. So I assume this is for the machine that
is not compliant to the spec. Is my understanding same as yours?

<snip.>

>   static int __devinit acpi_pci_root_add(struct acpi_device *device)
>   {
>   	unsigned long long segment, bus;
> @@ -504,6 +514,14 @@ static int __devinit acpi_pci_root_add(struct acpi_device *device)
>   	strcpy(acpi_device_class(device), ACPI_PCI_ROOT_CLASS);
>   	device->driver_data = root;
> 
> +	if (arch_acpi_pci_root_add(root)) {
> +		printk(KERN_ERR PREFIX
> +			"can't add MMCFG information for Bus %04x:%02x\n",
> +			root->segment, (unsigned int)root->secondary.start);
> +		result = -ENODEV;
> +		goto out_free;
> +	}

Desn't this break the system that doesn't support MMCONFIG?

In my understanding, arch_acpi_pci_root_add() returns -ENODEV if
mmconfig information is found neither in MCFG table nor _CBA. And
pci root bridge initialization seems to fail arch_acpi_pci_root_add()
returns non-zero value.

Regards,
Kenji Kaneshige
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