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

[Philippe Mathieu-Daudé]

On 7/9/20 4:15 PM, Peter Maydell wrote:
> 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).

Good catch...

> 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?

I am not sure what to recommend then.

Would that work as hint?

  qemu-system-arm -M raspi2 -sd ./buster-lite-armhf.img
  qemu-system-arm: Invalid SD card size: 1.73 GiB
  SD card size has to be a power of 2, e.g. 2GiB.