Re: [Qemu-devel] [PATCH] get roms more room.

[Carl-Daniel Hailfinger]

On 27.03.2009 18:37, Glauber Costa wrote:
> This patch increases by 50 % the size available for option roms.
> The main motivator is that some roms grew bigger than the 64k we
> currently allocate for them (Hey, it's 2009!)
>
> One example is the gpxe project, that produces some roms with 69k,
> 70k, etc. The space proposed by this patch actually makes it as
> big as 84k. Probably still a fit for some time.
>
> But there is no free lunch. This space must come from somewhere,
> and we take it from vga rom space. Currently, our vga roms are
> around 35k in size. With this patch, they will be limited to
> 44k, instead of 64k, which seems reasonable to me.
>   

As a firmware developer, I have to speak up here. Although I agree that
option ROMs may be bigger than 64k, replacing one hardcoded magic limit
with another hardcoded magic limit seems to be a bit questionable.

If you really want to hardcode this instead of calculating it
dynamically, please use at least some symbolic constants and tell the
user to change the symbolic constants and recompile Qemu if he hits the
size limit.

This patch reduces the room for the VGA option ROM without checking for
its size. If we perform option ROM size checks, we may as well not
exclude the VGA option ROM from that check.

AFAICS resuming an image created with the old memory layout will change
option ROM location and may lead to crashes, but I'm not so sure about that.

Regards,
Carl-Daniel

-- 
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