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    SubjectRe: [PATCH] x86/pci: do assign root bus res if _CRS is used
    Date
    On Monday 27 April 2009 02:15:33 pm Yinghai Lu wrote:
    > Bjorn Helgaas wrote:
    > > On Monday 20 April 2009 07:35:40 pm Yinghai Lu wrote:
    > >> it wil be overwriten later if _CRS is used, so don't bother to set it.
    > >>
    > >> [ Impact: cleanup ]
    > >>
    > >> Signed-off-by: Yinghai Lu <yinghai@kernel.org>
    > >>
    > >> ---
    > >> arch/x86/pci/amd_bus.c | 4 ++++
    > >> 1 file changed, 4 insertions(+)
    > >>
    > >> Index: linux-2.6/arch/x86/pci/amd_bus.c
    > >> ===================================================================
    > >> --- linux-2.6.orig/arch/x86/pci/amd_bus.c
    > >> +++ linux-2.6/arch/x86/pci/amd_bus.c
    > >> @@ -100,6 +100,10 @@ void x86_pci_root_bus_res_quirks(struct
    > >> int j;
    > >> struct pci_root_info *info;
    > >>
    > >> + /* don't go for it if _CRS is used */
    > >> + if (pci_probe & PCI_USE__CRS)
    > >> + return;
    > >> +
    > >> /* if only one root bus, don't need to anything */
    > >> if (pci_root_num < 2)
    > >> return;
    > >
    > > This isn't a comment on this patch per se.
    > >
    > > I am concerned about the fact that "pci=use_crs" is not the default.
    > > From the changelog of 62f420f8282, it sounds like you have to boot an
    > > IBM x3850 with "pci=use_crs" to make hot-plug work, even though ACPI
    > > tells us everything we need to know. That's backwards.
    > >
    > > We shouldn't need an option to tell Linux that the firmware is
    > > trustworthy. We should have an option to *ignore* it for the times
    > > when we trip over something broken and haven't figured out a way to
    > > work around it yet.
    >
    > other system may have broken _CRS.

    Do you have examples of problems here, or are you just worried that
    there *may* be problems?

    > maybe we could try to use DMI whitelist them?

    I don't like a whitelist because it requires ongoing maintenance
    for correctly-working machines. A blacklist is nicer because it
    only requires maintenance for *broken* machines. A date-based
    solution would be better from that point of view.

    Bjorn


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