Re: [Qemu-devel] [PATCH v3 03/10] raven: move BIOS loading from board code to PCI host

["Hervé Poussineau" <hpoussin@reactos.org>]

Peter Maydell a écrit :
> On 23 December 2013 06:48, Hervé Poussineau <hpoussin@reactos.org> wrote:
>> So, this patch is a small functional change, as it adds a copy of the
>> firmware in a new range 0xfff00000-0xfff7ffff, but I think we can live with
>> it.
>>
>> We'll be able to remove it once we switch to another firmware which uses the
>> right reset instruction pointer or whose size is 1MB.
>>
>>>> +    /* Open Hack'Ware hack: bios size is 512K and is loaded at
>>>> 0xfff00000.
>>>> +     * However, reset address is 0xfffffffc. Mirror the bios from
>>>> +     * 0xfff00000 to 0xfff80000.
>>>> +     */
>>>> +    memory_region_init_alias(bios, NULL, "bios-alias", sysmem,
>>>> 0xfff00000,
>>>> +                             0x00080000);
>>>> +    memory_region_add_subregion_overlap(sysmem, 0xfff80000, bios, 1);
> 
> This code creates the mirrored region regardless of the size of the
> firmware blob, right? I think that means that if we do supply a
> 1MB blob it'll do the wrong thing. You probably want to have some
> "mirror this object as many times as necessary to fill the space"
> logic.
> 
> We could probably do with having a generic MemoryRegion
> API for that, actually -- it's not uncommon behaviour for devices
> to be accessible every N bytes because they simply don't
> decode the full set of address lines.
> 
> memory_region_add_subregion_tiled(MemoryRegion *mr,
>                                  hwaddr offset, hwaddr tilelen,
>                                  MemoryRegion *subregion)
> 
> to add copies of subregion to container mr starting at offset
> for tilelen bytes, maybe? (we assume subregion to be created
> at the length that each 'tile' should be, so don't need to pass
> that too).

This hack is meant to exist only as long as OHW has not been replaced by 
something else. That's a hack which has to be used only for *current OHW 
firmware* (ie 512KB) and only for *a short time*. I've already patches 
to replace OHW by OpenBIOS, but some details need some more polish.

So, I don't want to invest too much time to polish this hack. Choose 
whatever you want, but I don't want to take more time to push this patchset.

If you really don't like it, I can provide a OHW image which is 1MB, so 
this hack becomes moot. It will be created by concatenating 2 512KB OHW 
images in a 1MB image.

Regards,

Hervé