Re: [Qemu-devel] RFC: raspberry pi / pi2 / Windows-on-ARM support

[Stefan Weil]

Am 16.11.2015 um 23:22 schrieb Andrew Baumann:
> Hi all,
> 
> I have been working on Raspberry Pi 2 emulation, building on the previous 
> work of Gregory Estrade, Stefan Weil and others on the original Raspberry Pi 
> target. My current working tree (based off a recent master) is here:
>     https://github.com/0xabu/qemu/tree/raspi
> 
> The present status is:
>  * The original Raspberry Pi (-M raspi) support works only with older kernels 
> from Raspbian releases up to 2014-09-09, for unknown reasons that I haven't 
> investigated. [1]
>  * Pi 2 (-M raspi2) supports both Raspbian and Windows.
>  * Raspbian boots on pi2, but fails on an implemented SETEND instruction in 
> early userspace. I'm told there are patches/workarounds for this floating 
> around, but have not tried them.
>  * The Windows IoT image [2] boots completely, but the USB emulation is 
> broken, so the only IO devices are framebuffer and serial console (which can 
> be used for a kernel debugger).
>  * All four Pi2 cores must be enabled for Windows, since the bootloader 
> panics if the expected cores are not present. Conversely, Raspbian fails to 
> boot if multiple cores are enabled, but I haven't debugged this, since qemu 
> is faster with a single-core guest.
> 
> I realise that getting this code integrated will require a series of smaller 
> patches, but wanted to solicit any early feedback before I start doing that. 
> I've verified that checkpatch.pl is happy, but if there are other stylistic 
> or general problems with the code it would be helpful to know about them 
> sooner rather than later :) If anyone has specific suggestions for how to 
> split up the patch, that would also be welcome. If not, I will start 
> submitting patches for the individual pieces, probably starting with the 
> machine definition and then the larger devices, followed by the 
> Windows-specific fixes described below.
> 
> There are also a couple of significant (non Pi-specific) changes that I made 
> in order to boot a Windows on ARM guest, which also I plan to submit:
> 1. UEFI (TianoCore / EDK2) has a couple of bugs in its MMC support -- it 
> assumes support for CMD23 (set multiple block count, which is supposed to be 
> optional), and also fails to initialise correctly if the card is ready 
> immediately upon issuing ACMD41. My tree includes workarounds for both issues 
> -- I implemented CMD23, and modelled a small delay when initialising the SD 
> card.
> 2. For better or worse, Windows relies on taking alignment faults on a 
> misaligned LDREX, however qemu doesn't perform any alignment checks, leading 
> to a bluescreen very early in boot. The changes in target-arm implement a 
> generic infrastructure for testing/raising alignment exceptions, and add a 
> suitable check to LDREX. (This is almost certainly applicable to arm64 as 
> well, but I don't have a means to test it.)
> 
> Here's the current diffstat (ignore the minor unrelated bugfixes in lan9118 
> and tap-win32):
>  default-configs/arm-softmmu.mak      |    1 +
>  hw/arm/Makefile.objs                 |    1 +
>  hw/arm/raspi.c                       |  514 ++++++++++++++++
>  hw/char/Makefile.objs                |    1 +
>  hw/char/bcm2835_aux.c                |  250 ++++++++
>  hw/display/Makefile.objs             |    1 +
>  hw/display/bcm2835_fb.c              |  384 ++++++++++++
>  hw/dma/Makefile.objs                 |    1 +
>  hw/dma/bcm2835_dma.c                 |  352 +++++++++++
>  hw/intc/Makefile.objs                |    1 +
>  hw/intc/bcm2835_ic.c                 |  248 ++++++++
>  hw/intc/bcm2836_control.c            |  373 ++++++++++++
>  hw/misc/Makefile.objs                |    5 +
>  hw/misc/bcm2835_mphi.c               |  176 ++++++
>  hw/misc/bcm2835_power.c              |  113 ++++
>  hw/misc/bcm2835_property.c           |  409 +++++++++++++
>  hw/misc/bcm2835_sbm.c                |  294 ++++++++++
>  hw/misc/bcm2835_vchiq.c              |  113 ++++
>  hw/net/lan9118.c                     |   18 +-
>  hw/sd/Makefile.objs                  |    1 +
>  hw/sd/bcm2835_emmc.c                 |  844 +++++++++++++++++++++++++++
>  hw/sd/sd.c                           |   78 ++-
>  hw/timer/Makefile.objs               |    2 +
>  hw/timer/arm_timer.c                 |   39 ++
>  hw/timer/bcm2835_st.c                |  201 +++++++
>  hw/timer/bcm2835_timer.c             |  242 ++++++++
>  hw/usb/Makefile.objs                 |    2 +
>  hw/usb/bcm2835_usb.c                 |  655 +++++++++++++++++++++
>  hw/usb/bcm2835_usb_regs.h            | 1061 
> ++++++++++++++++++++++++++++++++++
>  include/hw/arm/bcm2835_arm_control.h |  481 +++++++++++++++
>  include/hw/arm/bcm2835_common.h      |   35 ++
>  include/hw/arm/raspi_platform.h      |  155 +++++
>  net/tap-win32.c                      |   51 +-
>  target-arm/helper.c                  |    8 +
>  target-arm/helper.h                  |    1 +
>  target-arm/internals.h               |    3 +
>  target-arm/op_helper.c               |   21 +
>  target-arm/translate.c               |   29 +
>  38 files changed, 7141 insertions(+), 23 deletions(-)
> 
> The command line I've used for Raspbian is:
> qemu-system-arm -M raspi2 -m 1024 -kernel kernel7.img -sd 
> 2015-09-24-raspbian-jessie.img -append "rw earlyprintk loglevel=8 
> bcm2708_fb.fbwidth=1024 bcm2708_fb.fbheight=768 bcm2708.boardrev=0xf 
> bcm2708.serial=0xcad0eedf vc_mem.mem_base=0x1c000000 
> vc_mem.mem_size=0x20000000 dwc_otg.lpm_enable=0 root=/dev/mmcblk0p2"
> 
> The command line for Windows is:
> qemu-system-arm -M raspi2 -smp 4 -m 1024 -bios kernel.img -sd 
> th2preview_pi2_iot.vhd
> (where kernel.img is the EDK2 bootloader from the first partition of the 
> Windows image).
> 
> Cheers,
> Andrew
> 
> [1] https://www.raspberrypi.org/forums/viewtopic.php?f=72&t=26561&start=125
> [2] http://ms-iot.github.io/content/en-US/Downloads.htm
> 


Hi Andrew,

thanks for this great overview of your activities regarding QEMU with
Raspberry Pi 2 support.

The QEMU development is currently preparing the new version 2.5 (see
http://wiki.qemu.org/Planning/2.5, http://wiki.qemu.org/ChangeLog/2.5).
This should be finished until 2015-12-10 (maybe a little later).
New patches for RPi can be discussed earlier, but won't be applied
to Git master before version 2.5 is finished.

I wish you good luck and hope RPi will be available to all QEMU users
soon. This target should be added to http://wiki.qemu.org/Planning/2.6
(or will it be http://wiki.qemu.org/Planning/3.0?), so nobody forgets
it. :-)

Kind regards,
Stefan