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    SubjectRe: [PATCH 2/2] PCI, ACPI, x86: update MMCFG information when hot-plugging PCI host bridges
    Hi Kenji,
    Thanks for your careful review and comments.

    On 04/09/2012 07:43 PM, Kenji Kaneshige wrote:
    > 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.>
    Will try to generate a version against Bjorn's version. Could you please tell
    me the exact git link for that? I haven't pull from Bjorn's tree yet.

    >
    >> +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.>
    You are right, it's defined to that way in PCI FW Spec 3.1.
    Here I have some concerns about the PCI buses to host all Ubox components
    on Intel NHM/WSM/SNB/IVB processors. BIOS people are prone to declare
    MMCFG information for those host bridges by MCFG table instead of _CBA method,
    though those host bridge will disappear after hot-removing a physical processor.

    >
    >> 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.
    Good catch, will add following code into arch_acpi_pci_root_add() and
    arch_acpi_pci_root_remove() to solve this issue.
    ---
    /* MMCONFIG disabled */
    if ((pci_probe & PCI_PROBE_MMCONF) == 0)
    return 0;
    ---


    >
    > Regards,
    > Kenji Kaneshige



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