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vm_minimal, QEMU: block aarch32 build
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The QEMU/aarch32 platform is not supported actively at the moment for
virtualization.

Signed-off-by: Axel Heider <[email protected]>
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@axel-h @lsf37
axel-h authored and lsf37 committed Mar 16, 2024
1 parent 6656ebe commit 977022b
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8 changes: 8 additions & 0 deletions apps/Arm/vm_minimal/CMakeLists.txt
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Expand Up @@ -86,6 +86,14 @@ elseif("${KernelARMPlatform}" STREQUAL "tx2")
AddToFileServer("linux-dtb" "${output_dtb_location}" DEPENDS dtb_gen_target)

elseif("${KernelARMPlatform}" STREQUAL "qemu-arm-virt")

# QEMU supports ARMv7/aarch32 and ARMv8/aarch32, but currently there are
# Linux images for aarch64 only. However, it is unclear if that is the only
# blocker to get this example run in QEMU on aarch32.
if(NOT KernelSel4ArchAarch64)
message(FATAL_ERROR "Only AARCH64 is supported")
endif()

find_package(camkes-vm-linux REQUIRED)
include(${CAMKES_VM_LINUX_HELPERS_PATH})
set(cpp_flags "-DKERNELARMPLATFORM_QEMU-ARM-VIRT")
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3 comments on commit 977022b

@j1mst1x
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Oh boy, so with this change (or maybe with the change that caused this to have to be implemented), you have to initialize the qemu-arm-virt build with -DAARCH64=1 in order to get the qemu-arm-virt examples to work. That's about an hour of my life I want back :-)

Example to get vm_minimal working:

$ cd build
$ ../init-build.sh -DCAMKES_VM_APP=vm_minimal -DPLATFORM=qemu-arm-virt -DAARCH64=1
$ ninja
$ ./simulate

I feel like a hint on the main git page should be added for this or a hint to the compilation error?

Anyways hopefully this saves someone else some time in the future.

@lsf37
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@lsf37 lsf37 commented on 977022b Jun 13, 2024

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You're right, at least an example and explanation in the docs for qemu-arm-virt would be good. If that was mentioned in the camkes-vm-examples repo README, would you have found it there or did you get here by another path?

@j1mst1x
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TL;DR: I think mentioning it in the notes column in the ARM Features table in the camkes-vm-examples repo README would be sufficient.

Honestly I'm coming back to seL4 for a new project after a few years away and I was doing the tutorials. Well I got to the cross vm tutorial, I remembered it was broken because y'all switched from a character device to a userspace IO device. I went to compile the cross-vm for qemu-arm-virt and it page faulted... which I thought was weird so I tried vm_minimal and it page faulted as well. After some investigation I saw that the default processor was getting set to something like a A15 and that if I set the AARCH64 switch it would use an A53.

Then all of a sudden this commit made a lot more sense to me. Anyways, there's an arguement to be made that this is why vm_minimal64 exists... but then that would break all of the other examples. So I think adding a note in bold in the ARM Features table for QEMU is the way to go.

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