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    SubjectRe: [PATCH] x86/pci: intel ioh need to subtract mmconf range
    Date
    On Thursday 14 January 2010 04:38:08 pm Yinghai Lu wrote:
    > On 01/14/2010 03:09 PM, Bjorn Helgaas wrote:
    > > On Thursday 14 January 2010 03:46:35 pm Yinghai Lu wrote:
    > >>
    > >> Bjorn pointed out we need to remove mmconf range
    > >>
    > >> Signed-off-by: Yinghai Lu <yinghai@kernel.org>
    > >>
    > >> ---
    > >> arch/x86/pci/intel_bus.c | 29 +++++++++++++++++++++++++++--
    > >> 1 file changed, 27 insertions(+), 2 deletions(-)
    > >>
    > >> Index: linux-2.6/arch/x86/pci/intel_bus.c
    > >> ===================================================================
    > >> --- linux-2.6.orig/arch/x86/pci/intel_bus.c
    > >> +++ linux-2.6/arch/x86/pci/intel_bus.c
    > >> @@ -46,6 +46,20 @@ static inline void print_ioh_resources(s
    > >>
    > >> #define RANGE_NUM 16
    > >>
    > >> +static void __devinit subtract_mmconf(struct range *range, int nr)
    > >> +{
    > >> +#ifdef CONFIG_PCI_MMCONFIG
    > >> + struct pci_mmcfg_region *cfg;
    > >> +
    > >> + if (list_empty(&pci_mmcfg_list))
    > >> + return;
    > >> +
    > >> + list_for_each_entry(cfg, &pci_mmcfg_list, list)
    > >> + subtract_range(range, nr, cfg->res.start,
    > >> + cfg->res.end + 1);
    > >> +#endif
    > >
    > > This can't be right, can it? Let's say the kernel was built with
    > > CONFIG_PCI_MMCONFIG turned off, or the user used "pci=nommconf",
    > > or the kernel decides not to use MMCONFIG for some other reason.
    > >
    > > In that case, the hardware may still be configured to support
    > > MMCONFIG, but the pci_mmcfg_list will be empty, so your code will
    > > leave the window alone. We might assign some of that MMCONFIG
    > > space to a device, but the hardware will route it to MMCONFIG,
    > > not to the device.
    >
    > so if there is mmconf specified, we just skip the whole function?

    No, I'm saying that intel-bus.c must ALWAYS remove the MMCONFIG region
    from the host bridge apertures, even if Linux isn't using MMCONFIG.

    That means intel-bus.c has to be smart enough to figure out on its
    own what the MMCONFIG area is. It can't depend on mmconfig-shared.c
    to do it, because mmconfig-shared.c might not be there.

    Bjorn


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