Re: [PATCH 2/2] hw/sd/sdcard: Do not allow invalid SD card sizes

[Peter Maydell <peter.maydell@linaro.org>]

On Thu, 9 Jul 2020 at 14:56, Philippe Mathieu-Daudé <f4bug@amsat.org> wrote:
>
> On 7/7/20 10:29 PM, Niek Linnenbank wrote:
> > So I manually copy & pasted the change into hw/sd/sd.c to test it.
> > It looks like the check works, but my concern is that with this change,
> > we will be getting this error on 'off-the-shelf' images as well.
> > For example, the latest Raspbian image size also isn't a power of two:
> >
> > $ ./arm-softmmu/qemu-system-arm -M raspi2 -sd
> > ~/Downloads/2020-05-27-raspios-buster-lite-armhf.img -nographic
> > WARNING: Image format was not specified for
> > '/home/me/Downloads/2020-05-27-raspios-buster-lite-armhf.img' and
> > probing guessed raw.
> >          Automatically detecting the format is dangerous for raw images,
> > write operations on block 0 will be restricted.
> >          Specify the 'raw' format explicitly to remove the restrictions.
> > qemu-system-arm: Invalid SD card size: 1.73 GiB (expecting at least 2 GiB)
> >
> > If we do decide that the change is needed, I would like to propose that
> > we also give the user some instructions
> > on how to fix it, maybe some 'dd' command?
>
> On POSIX we can suggest to use 'truncate -s 2G' from coreutils.
> This is not in the default Darwin packages.
> On Windows I have no clue.

dd/truncate etc won't work if the image file is not raw (eg if
it's qcow2). The only chance you have of something that's actually
generic would probably involve "qemu-img resize". But I'm a bit
wary of having an error message that recommends that, because
what if we got it wrong?

thanks
-- PMM