On Tue, 18 Feb 2020 at 06:46, Philippe Mathieu-Daudé <phi...@redhat.com> wrote: > IIRC from the specs, cards are block devices and the only alignment > required is the size of a block (512KiB for your 4GiB card).
Isn't there something related to erase blocks too, which impose a larger granularity than just a single block? Anyway, in general the backing image for an SD card device needs to be exactly the size of the SD card you're emulating, because QEMU needs somewhere it can write back the data if the guest decides to write to the last block on the card. So short-length images generally don't work (true for all block devices, not just SD cards, I think). This often bites users if they're using some distro "here's a disk/sd card image file" where the expected use with real hardware is "dd the image file onto the SD card". thanks -- PMM
