Crash with QEMU(x86_64) >= pc-i440fx-7.1 and TCG and paging

[skuenzer]

Describe the bug

Unikraft's KVM platform library crashes early during boot on x86_64 with TCG (no KVM virtualization) with Paging API enabled. This only happens with QEMU pc models starting from 7.1: pc-i440fx-7.1, pc-i440fx-7.2, ...
I could not reproduce the crash with KVM acceleration (Tested on GCP Debian11 Linux: 5.10.0-23-cloud-amd64).

A workaround for avoiding the crash (failing assertion) can be achieved by using an QEMU pc machine model < 7.1: like pc-i440fx-7.0.

Steps to reproduce

It can be reproduced just with Unikraft (x86_64) and the following settings. The important one that causes the crash is CONFIG_PAGING-y:

CONFIG_PLAT_KVM=y
# CONFIG_KVM_KERNEL_VGA_CONSOLE is not set
# CONFIG_KVM_DEBUG_VGA_CONSOLE is not set
# CONFIG_KVM_PCI is not set
CONFIG_PAGING=y
CONFIG_LIBUKDEBUG_PRINTK_INFO=y
CONFIG_LIBUKDEBUG_PRINTD=y

QEMU (must be version >= 7.1) can be launched with:

qemu-system-x86_64 \
    -machine pc,accel=tcg -cpu qemu64,-vmx,-svm,+pdpe1gb \
    -nographic \
    -vga none \
    -display none
    -m 64 \
    -net none \
    -kernel build/unikraft_qemu-x86_64 \

Expected behavior

The crash should not appear and the system should continue booting further, up to the application.

Which architectures were you using or does this bug affect?

x86_64

Which platforms were you using or does this bug affect?

kvm

Relevant log output

SeaBIOS (version rel-1.16.2-0-gea1b7a073390-prebuilt.qemu.org)
Booting from ROM..[    0.000000] dbg:  [libukfallocbuddy] <fallocbuddy.c @  932> ffffff8000012000: Adding physical memory 13000 - 14000 ()
[    0.000000] dbg:  [libukfallocbuddy] <fallocbuddy.c @  932> ffffff8000012000: Adding physical memory 14000 - 18000 (fl 2, 16384)
[    0.000000] dbg:  [libukfallocbuddy] <fallocbuddy.c @  932> ffffff8000012000: Adding physical memory 18000 - 20000 (fl 3, 32768)
[    0.000000] dbg:  [libukfallocbuddy] <fallocbuddy.c @  932> ffffff8000012000: Adding physical memory 20000 - 40000 (fl 5, 131072)
[    0.000000] dbg:  [libukfallocbuddy] <fallocbuddy.c @  932> ffffff8000012000: Adding physical memory 40000 - 80000 (fl 6, 262144)
[    0.000000] dbg:  [libukfallocbuddy] <fallocbuddy.c @  932> ffffff8000012000: Adding physical memory 80000 - 90000 (fl 4, 65536)
[    0.000000] dbg:  [libukfallocbuddy] <fallocbuddy.c @  932> ffffff8000012000: Adding physical memory 90000 - 98000 (fl 3, 32768)
[    0.000000] dbg:  [libukfallocbuddy] <fallocbuddy.c @  932> ffffff8000012000: Adding physical memory 98000 - 9c000 (fl 2, 16384)
[    0.000000] dbg:  [libukfallocbuddy] <fallocbuddy.c @  932> ffffff8000012000: Adding physical memory 9c000 - 9e000 (fl 1, 8192)
[    0.000000] dbg:  [libukfallocbuddy] <fallocbuddy.c @  932> ffffff8000012000: Adding physical memory 9e000 - 9f000 (fl 0, 4096)
[    0.000000] dbg:  [libukfallocbuddy] <fallocbuddy.c @  932> ffffff8000012000: Adding physical memory 174000 - 178000 (fl 2, 16384)
[    0.000000] dbg:  [libukfallocbuddy] <fallocbuddy.c @  932> ffffff8000012000: Adding physical memory 178000 - 180000 (fl 3, 32768)
[    0.000000] dbg:  [libukfallocbuddy] <fallocbuddy.c @  932> ffffff8000012000: Adding physical memory 180000 - 200000 (fl 7, 524288)
[    0.000000] dbg:  [libukfallocbuddy] <fallocbuddy.c @  932> ffffff8000012000: Adding physical memory 200000 - 400000 (fl 9, 2097152)
[    0.000000] dbg:  [libukfallocbuddy] <fallocbuddy.c @  932> ffffff8000012000: Adding physical memory 400000 - 800000 (fl 10, 4194304)
[    0.000000] dbg:  [libukfallocbuddy] <fallocbuddy.c @  932> ffffff8000012000: Adding physical memory 800000 - 1000000 (fl 11, 8388608)
[    0.000000] dbg:  [libukfallocbuddy] <fallocbuddy.c @  932> ffffff8000012000: Adding physical memory 1000000 - 2000000 (fl 12, 1677721)
[    0.000000] dbg:  [libukfallocbuddy] <fallocbuddy.c @  932> ffffff8000012000: Adding physical memory 2000000 - 3000000 (fl 12, 1677721)
[    0.000000] dbg:  [libukfallocbuddy] <fallocbuddy.c @  932> ffffff8000012000: Adding physical memory 3000000 - 3800000 (fl 11, 8388608)
[    0.000000] dbg:  [libukfallocbuddy] <fallocbuddy.c @  932> ffffff8000012000: Adding physical memory 3800000 - 3c00000 (fl 10, 4194304)
[    0.000000] dbg:  [libukfallocbuddy] <fallocbuddy.c @  932> ffffff8000012000: Adding physical memory 3c00000 - 3e00000 (fl 9, 2097152)
[    0.000000] dbg:  [libukfallocbuddy] <fallocbuddy.c @  932> ffffff8000012000: Adding physical memory 3e00000 - 3f00000 (fl 8, 1048576)
[    0.000000] dbg:  [libukfallocbuddy] <fallocbuddy.c @  932> ffffff8000012000: Adding physical memory 3f00000 - 3f80000 (fl 7, 524288)
[    0.000000] dbg:  [libukfallocbuddy] <fallocbuddy.c @  932> ffffff8000012000: Adding physical memory 3f80000 - 3fc0000 (fl 6, 262144)
[    0.000000] dbg:  [libukfallocbuddy] <fallocbuddy.c @  932> ffffff8000012000: Adding physical memory 3fc0000 - 3fe0000 (fl 5, 131072)
[    0.000000] CRIT: [libkvmplat] <paging.c @  541> Assertion failure: ukarch_paddr_range_isvalid(paddr, paddr + len)
[    0.000000] Info: [libkvmplat] <shutdown.c @   59> Unikraft halted