Re: [SeaBIOS] [PATCH 4/4] pci: runtime i/o window sizing

[Kevin O'Connor]

On Thu, Jun 07, 2012 at 10:34:34AM +0200, Gerd Hoffmann wrote:
> Update the pci i/o windows at runtime, depending on the amount memory
> the machine has.  The 32bit window starts above low memory and ends at
> the ioapic map address, the 64bit window is placed above high memory.

[...]
>    r64_mem.base = pcimem64_start;
>    u64 sum = pci_region_sum(&r64_mem);
>    u64 align = pci_region_align(&r64_pref);
>    r64_pref.base = ALIGN(r64_mem.base + sum, align);
>    for (i = 0; i < ARRAY_SIZE(sizes); i++) {
>        pcimem64_size = sizes[i];
>        pcimem64_start = ALIGN(0x100000000LL + RamSizeOver4G, pcimem64_size);

Why align to 64GB (or 1TB)?  How about just starting at 4GB past ram
aligned to 4GB.
>        pcimem64_end = pcimem64_start + pcimem64_size;
>        r64_mem.base = pcimem64_start;
>        u64 sum = pci_region_sum(&r64_mem);
>        u64 align = pci_region_align(&r64_pref);
>        r64_pref.base = ALIGN(r64_mem.base + sum, align);
>        if (r64_pref.base + pci_region_sum(&r64_pref) <= pcimem64_end)
>            break;

Why not just assign "pcimem64_end = r64_pref.base +
pci_region_sum(&r64_pref)" instead?  That is, instead of looping to
try certain sizes, why not just set the range according to how much
space is found to be needed?

-Kevin