Re: [PATCH] [9/50] i386: validate against ACPI motherboard resources

["Yinghai Lu" <yhlu.kernel@gmail.com>]

On 9/22/07, Robert Hancock <hancockr@shaw.ca> wrote:
> Yinghai Lu wrote:
> > On 9/22/07, Robert Hancock <hancockr@shaw.ca> wrote:
> >> Thomas Gleixner wrote:
> >>> On Sat, 2007-09-22 at 10:28 -0600, Robert Hancock wrote:
> >>>> Yinghai Lu wrote:
> >>>>> No!
> >>>>>
> >>>>> MMCONFIG will not work with acpi=off any more.
> >>>> I don't think this is unreasonable. The ACPI MCFG table is how we are
> >>>> supposed to learn about the area in the first place. If we can't get the
> >>>> table location via an approved mechanism, and can't validate it doesn't
> >>>> overlap with another memory reservation or something, I really don't
> >>>> think we should be using it.
> >>> We all know how correct ACPI tables are. Specifications are nice,
> >>> reality tells a different story.
> >> MMCONFIG can't be used without ACPI in any case unless we know where the
> >>   table is using chipset-specific knowledge (i.e. reading the registers
> >> directly). Doing that without being told that this area is really
> >> intended to be used, via the ACPI table, is dangerous, i.e. we don't
> >> necessarily know if the MMCONFIG is broken on the platform in some way
> >> we can't detect.
> >
> > the BIOS get these info from the chipset too.
> > for AMD Fam 10h opteron, we can read that MSR for MMCONFIG base.
> >
> >>>> I don't think it's much of an issue anyway - the chances that somebody
> >>>> will want to run without ACPI on a system with MCFG are pretty low given
> >>>> that you'll end up losing a bunch of functionality (not least of which
> >>>> is multi-cores).
> >>> acpi=off is an often used debug switch and it _is_ quite useful. Taking
> >>> away debug functionality is not a good idea.
> >> If someone has to turn ACPI off, disabling MMCONFIG is probably the
> >> least of their worries..
> >
> > MMCONFIG has nothing to do ACPI..., just becase MCFG in the ACPI, we
> > must use ACPI for MMCONFIG?
>
> config PCI_MMCONFIG
>           bool
>           depends on PCI && ACPI && (PCI_GOMMCONFIG || PCI_GOANY)
>           default y
>
> We already depend on ACPI for MMCONFIG support at compile time. This
> patch does not change that.
>
> We could conceivably skip the validation if ACPI was disabled, though
> this would only make a difference in the few cases where we can detect
> the MMCONFIG area without it (looks like currently only Intel E7520 and
> 945, at least in mainline).

i added support for AMD Fam 10h NB, and that patch is in -mm.

I like to see pci_mmcfg_check_hostbridge is called before any acpi check up.

also in your pci_mmcfg_early_init, you may miss calling to
pci_mmcfg_insert_resource...

YH
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