Re: [coreboot] Resource Allocator for v3

[ron minnich]

On Mon, Nov 24, 2008 at 7:01 AM, Myles Watson  wrote:
>            if (resource->flags & IORESOURCE_IO) {
>                    /* Don't allow potential aliases over the legacy PCI
>                     * expansion card addresses. The legacy PCI decodes
>                     * only 10 bits, uses 0x100 - 0x3ff. Therefore, only
>                     * 0x00 - 0xff can be used out of each 0x400 block
>
> of
>                         * I/O space.
>                         */
>                        if ((base & 0x300) != 0) {
>                                base = (base & ~0x3ff) + 0x400;
>                        }
>                        /* Don't allow allocations in the VGA I/O range.
>                         * PCI has special cases for that.
>                         */
>                        else if ((base >= 0x3b0) && (base <= 0x3df)) {
>                                base = 0x3e0;
>                        }
>                }
>
> It seems like I'm misreading this and/or the check isn't broad enough.  If
> there are really devices claiming all IO where the last 10 bits decode to
> 0x300, then many more ranges should be affected.  For example, a size 0x200
> allocation from 0x200-0x3ff doesn't trigger this check.  Neither does a size
> 0x200 allocation from 0x1200 - 0x13ff, but a size 0x20 allocation from
> 0x1320-0x133f does.

I don't understand. 0x200 & 0x300 is non-zero. 0x200 will trigger it.
> My theory is that this only matters for devices that are subtractively
> decoding the address space.  At least in the k8 case, the 0x1200-0x13ff
> range transactions will never conflict with the "legacy PCI" unless the
> device is on the southbridge.  If it's anywhere else, the HT routing means
> that the southbridge will never see the transaction.

good point.

ron