Comment 6 for bug 1892604

for me the output is:
% qemu-system-arm -M raspi2 -m 1G -dtb bcm2709-rpi-2-b.dtb -kernel kernel7.img -append "rw earlyprintk loglevel=8 console=ttyAMA0,115200 dwc_otg.lpm_enable=0 root=/dev/mmcblk0p2" -sd 2016-05-27-raspbian-jessie.img -smp 4 -serial stdio -display none

WARNING: Image format was not specified for '2016-05-27-raspbian-jessie.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: 3.74 GiB
SD card size has to be a power of 2, e.g. 4 GiB.
You can resize disk images with 'qemu-img resize <imagefile> <new-size>'
(note that this will lose data if you make the image smaller than it currently is).