[Bug 1910586] [NEW] SD card size constraint conceptually wrong

[-]

Public bug reported:

The patch discussed here:
https://www.mail-archive.com/qemu-devel@nongnu.org/msg720833.html
introduces an artificial size constraint for SD cards
that has no relation to reality.

I'm trying to use an _actual_ **physical** SD card,
and qemu tells me its size is "invalid".

Something here appears to be conceptually wrong.

--------------------------------------------------
# fdisk -l /dev/sdg
Disk /dev/sdg: 14.84 GiB, 15931539456 bytes, 31116288 sectors
Disk model: USB  SD Reader  
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x7a0c8bb0

Device     Boot  Start      End  Sectors  Size Id Type
/dev/sdg1         2048   524287   522240  255M  c W95 FAT32 (LBA)
/dev/sdg2       524288 31116287 30592000 14.6G 83 Linux
# qemu-system-aarch64 -M raspi3 -m 1G -kernel vmlinuz-5.4.79-v8 -dtb 
bcm2837-rpi-3-b-plus.dtb -append console=ttyAMA0\ root=/dev/mmcblk0p2\ rw 
-nographic -serial mon:stdio -drive file=/dev/sdg,format=raw
qemu-system-aarch64: Invalid SD card size: 14.8 GiB
SD card size has to be a power of 2, e.g. 16 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).
--------------------------------------------------

The same invocation with a dump of the actual image
resized to match qemu's odd expectations works fine.


This is on QEMU 5.2.0, as evidenced by the following:
--------------------------------------------------
# qemu-system-aarch64 -version
QEMU emulator version 5.2.0
Copyright (c) 2003-2020 Fabrice Bellard and the QEMU Project developers
--------------------------------------------------

Is there a simple workaround that disables this rather
arbitrary constraint?

** Affects: qemu
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/1910586

Title:
  SD card size constraint conceptually wrong

Status in QEMU:
  New

Bug description:
  The patch discussed here:
  https://www.mail-archive.com/qemu-devel@nongnu.org/msg720833.html
  introduces an artificial size constraint for SD cards
  that has no relation to reality.

  I'm trying to use an _actual_ **physical** SD card,
  and qemu tells me its size is "invalid".

  Something here appears to be conceptually wrong.

  --------------------------------------------------
  # fdisk -l /dev/sdg
  Disk /dev/sdg: 14.84 GiB, 15931539456 bytes, 31116288 sectors
  Disk model: USB  SD Reader  
  Units: sectors of 1 * 512 = 512 bytes
  Sector size (logical/physical): 512 bytes / 512 bytes
  I/O size (minimum/optimal): 512 bytes / 512 bytes
  Disklabel type: dos
  Disk identifier: 0x7a0c8bb0

  Device     Boot  Start      End  Sectors  Size Id Type
  /dev/sdg1         2048   524287   522240  255M  c W95 FAT32 (LBA)
  /dev/sdg2       524288 31116287 30592000 14.6G 83 Linux
  # qemu-system-aarch64 -M raspi3 -m 1G -kernel vmlinuz-5.4.79-v8 -dtb 
bcm2837-rpi-3-b-plus.dtb -append console=ttyAMA0\ root=/dev/mmcblk0p2\ rw 
-nographic -serial mon:stdio -drive file=/dev/sdg,format=raw
  qemu-system-aarch64: Invalid SD card size: 14.8 GiB
  SD card size has to be a power of 2, e.g. 16 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).
  --------------------------------------------------

  The same invocation with a dump of the actual image
  resized to match qemu's odd expectations works fine.

  
  This is on QEMU 5.2.0, as evidenced by the following:
  --------------------------------------------------
  # qemu-system-aarch64 -version
  QEMU emulator version 5.2.0
  Copyright (c) 2003-2020 Fabrice Bellard and the QEMU Project developers
  --------------------------------------------------

  Is there a simple workaround that disables this rather
  arbitrary constraint?

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