Re: [Qemu-devel] [Qemu-ppc] [PATCH 05/10] ppc405_boards: Don't size flash memory to match backing image

[Markus Armbruster <armbru@redhat.com>]

BALATON Zoltan <balaton@eik.bme.hu> writes:

> On Mon, 18 Feb 2019, Markus Armbruster wrote:
>> Machine "ref405ep" maps its flash memory at address 2^32 - image size.
>> Image size is rounded up to the next multiple of 64KiB.  Useless,
>> because pflash_cfi02_realize() fails with "failed to read the initial
>> flash content" unless the rounding is a no-op.
>>
>> If the image size exceeds 0x80000 Bytes, we overlap first SRAM, then
>> other stuff.  No idea how that would play out, but a useful outcomes
>> seem unlikely.
>>
>> Map the flash memory at fixed address 0xFFF80000 with size 512KiB,
>> regardless of image size, to match the physical hardware.
>
> If PPC405 behaves the same as PPC440 and starts at 0xfffffffc then
> this won't boot. It's maybe better to keep 2^32 - image_size but
> assert image is not bigger than 512kB. But I don't know anything about
> these boards so just sharing this comment for your consideration. I'm
> fine with any decision you take.

If the image is smaller than 512KiB, pflash_cfi02_realize() fails with
"failed to read the initial flash content".

Alex Bennée has a patch that'll make it fail for any size mismatch, with
a much nicer error message.  I like it; silently truncating firmware
images is unlikely to be useful.

For what it's worth, my patch brings this board into line with most
other boards: create flash memory of fixed size at a fixed address,
matching the physical machine we emulate.