armhf VMs broken with more than 3GB of RAM

[Skia]

Hi,

During some autopkgtest debugging, we found that we were unable to boot an armhf virtual machine with more than 3GB of RAM.

Here is the working command line:
```
qemu-system-arm \
-machine virt -m 3G -smp 2 -nographic \
-object rng-random,filename=/dev/urandom,id=rng0 \
-device virtio-rng-pci,rng=rng0,id=rng-device0 \
-drive if=pflash,format=raw,unit=0,read-only=on,file=/usr/share/AAVMF/AAVMF32_CODE.fd \
-device virtio-net-pci,netdev=eth0 \
-netdev user,id=eth0,hostfwd=tcp::8022-:22 \
-drive file=autopkgtest-noble-armhf.img,if=virtio,format=qcow2
```
And here is the broken one, that ends up in a loop of `watchdog: BUG: soft lockup - CPU#1 stuck for 26s!`:
```
qemu-system-arm \
-machine virt -m 4G -smp 2 -nographic \
-object rng-random,filename=/dev/urandom,id=rng0 \
-device virtio-rng-pci,rng=rng0,id=rng-device0 \
-drive if=pflash,format=raw,unit=0,read-only=on,file=/usr/share/AAVMF/AAVMF32_CODE.fd \
-device virtio-net-pci,netdev=eth0 \
-netdev user,id=eth0,hostfwd=tcp::8022-:22 \
-drive file=autopkgtest-noble-armhf.img,if=virtio,format=qcow2
```

Some early boot details:

3GB RAM:
```
[ 0.000000] Linux version 6.5.0-9-generic (buildd@bos02-arm64-028) (arm-linux-gnueabihf-gcc-13 (Ubuntu 13.2.0-4ubuntu3) 13.2.0, GNU ld (GNU Binutils for Ubuntu) 2.41) #9-Ubuntu SMP Fri Oct 6 23:14:49 UTC 2023 (Ubuntu 6.5.0-9.9-generic 6.5.3)
[ 0.000000] CPU: ARMv7 Processor [414fc0f0] revision 0 (ARMv7), cr=30c5387d
[ 0.000000] CPU: div instructions available: patching division code
[ 0.000000] CPU: PIPT / VIPT nonaliasing data cache, PIPT instruction cache
[ 0.000000] OF: fdt: Machine model: linux,dummy-virt
[ 0.000000] random: crng init done
[ 0.000000] Memory policy: Data cache writealloc
[ 0.000000] efi: EFI v2.7 by Ubuntu distribution of EDK II
[ 0.000000] efi: SMBIOS=0xfffee000 SMBIOS 3.0=0xfffec000 MEMATTR=0xfe991a90 INITRD=0xfc727e90 RNG=0xfc72c010 MEMRESERVE=0xfc727d90
[ 0.000000] secureboot: Secure boot disabled
[ 0.000000] cma: Reserved 32 MiB at 0x00000000fc800000
[ 0.000000] Zone ranges:
[ 0.000000] DMA [mem 0x0000000040000000-0x000000006fffffff]
[ 0.000000] Normal empty
[ 0.000000] HighMem [mem 0x0000000070000000-0x00000000ffffffff]
[ 0.000000] Movable zone start for each node
[ 0.000000] Early memory node ranges
[ 0.000000] node 0: [mem 0x0000000040000000-0x00000000ffc16fff]
[ 0.000000] node 0: [mem 0x00000000ffc17000-0x00000000ffffefff]
[ 0.000000] node 0: [mem 0x00000000fffff000-0x00000000ffffffff]
[ 0.000000] Initmem setup node 0 [mem 0x0000000040000000-0x00000000ffffffff]
```

4GB RAM:
```
[ 0.000000] Linux version 6.5.0-9-generic (buildd@bos02-arm64-028) (arm-linux-gnueabihf-gcc-13 (Ubuntu 13.2.0-4ubuntu3) 13.2.0, GNU ld (GNU Binutils for Ubuntu) 2.41) #9-Ubuntu SMP Fri Oct 6 23:14:49 UTC 2023 (Ubuntu 6.5.0-9.9-generic 6.5.3)
[ 0.000000] CPU: ARMv7 Processor [414fc0f0] revision 0 (ARMv7), cr=30c5387d
[ 0.000000] CPU: div instructions available: patching division code
[ 0.000000] CPU: PIPT / VIPT nonaliasing data cache, PIPT instruction cache
[ 0.000000] OF: fdt: Machine model: linux,dummy-virt
[ 0.000000] random: crng init done
[ 0.000000] Memory policy: Data cache writealloc
[ 0.000000] efi: EFI v2.7 by Ubuntu distribution of EDK II
[ 0.000000] efi: SMBIOS=0xfffee000 SMBIOS 3.0=0xfffec000 MEMATTR=0xfe991a90 INITRD=0xfc727e90 RNG=0xfc72c010 MEMRESERVE=0xfc727d90
[ 0.000000] secureboot: Secure boot disabled
[ 0.000000] cma: Reserved 32 MiB at 0x00000000fc800000
[ 0.000000] Zone ranges:
[ 0.000000] DMA [mem 0x0000000040000000-0x000000006fffffff]
[ 0.000000] Normal empty
[ 0.000000] HighMem [mem 0x0000000070000000-0x000000013fffffff]
[ 0.000000] Movable zone start for each node
[ 0.000000] Early memory node ranges
[ 0.000000] node 0: [mem 0x0000000040000000-0x00000000ffc16fff]
[ 0.000000] node 0: [mem 0x00000000ffc17000-0x00000000ffffefff]
[ 0.000000] node 0: [mem 0x00000000fffff000-0x000000013fffffff]
[ 0.000000] Initmem setup node 0 [mem 0x0000000040000000-0x000000013fffffff]
```

Here is my version of EDK2: `qemu-efi-arm/mantic,now 2023.05-2 all [installed,automatic]`

Let me know if further details are needed.

[Mate Kukri (mkukri)]

My version of qemu-system-arm doesn't even get to the kernel with >2G of RAM, the firmware just locks up.

[Mate Kukri (mkukri)]

Looks like that's related to the Debian version of AAVMF... Despite having the exact same version number, I managed to reproduce it with the noble qemu-efi-arm package.

[Mate Kukri (mkukri)]

I don't think this is an EDK2 bug anymore, it looks more like a qemu-system-arm bug. AAVMF32 + armhf kernel boots fine in qemu-system-aarch64 with 8GiB of RAM:
```
qemu-system-aarch64 \
 -machine virt \
 -m 8G \
 -drive if=pflash,format=raw,unit=0,readonly=on,file=AAVMF32_CODE.fd \
 -drive if=pflash,format=raw,unit=1,file=AAVMF32_VARS.fd \
 -drive file=autopkgtest-noble-armhf.img,if=virtio,format=qcow2
```

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.