Messages in this thread | | | Date | Tue, 10 Apr 2012 19:32:28 +0900 | From | Kenji Kaneshige <> | Subject | Re: [PATCH 2/2] PCI, ACPI, x86: update MMCFG information when hot-plugging PCI host bridges |
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(2012/04/10 1:02), Jiang Liu wrote: > 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.
As you may know, it was announced _today_ (sorry:).
http://www.spinics.net/lists/linux-pci/msg14626.html
> >> >>> +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.
Ok, thank you for clarification.
> >> >>> 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);
Additional comment.
This printk message looks strange because arch_acpi_pci_root_add() is not a mmconfig specific function. So I think this message should be moved to arch specific code (arch_acpi_pci_root_add()).
>>> + 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; > ---
My understanding is that PCI_PROBE_MMCONF is set even if the system doesn't have MCFG table. So I don't think this solves the issue. I guess this is what Yinghai pointed out on your V2 patch [6/6].
Additionally, I think there is a remaining issue even if we change this check like below.
if (!!(pci_probe & PCI_PROBE_MASK & ~PCI_PROBE_MMCONF)) return 0;
I think this check has an assumption that system has at least one MCFG table entry and it has been initialized before acpi_pci_root_add() is called. I think this doesn't work on the system that doesn't have MCFG and all the pci root bridge have _CBA (that is, all host bridges are hot-pluggable and BIOS is implemented in the way PCI FW spec defines). As a result, MMCONFIG would never be enabled on such systems. Could you double check this?
Regards, Kenji Kaneshige
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