About

This is a project related to SE_01_005 - QEMU PCIe passthru on x86 hosts.

When enabling PCIe passthru on x86 hosts, the physical memory range of 3GB-4GB is reserved for this purpose.

If the RAM memory size is larger than 1GB, it's split into low and high memory, e.g, for a 3GB RAM space:

• low memory - 2GB to 3GB
• high memory - 4GB to 6GB

However, u-boot is not able to handle this situation and failed as follows:

The command line:

qemu-system-riscv64 -machine virt -nographic -m 3072 -smp 4 \
        -bios /usr/lib/riscv64-linux-gnu/opensbi/generic/fw_jump.elf \
        -kernel /usr/lib/u-boot/qemu-riscv64_smode/uboot.elf \
        -netdev user,id=vnet,hostfwd=:127.0.0.1:2223-:22 -device virtio-net-pci,netdev=vnet \
        -device vfio-pci,host=01:00.0 -device vfio-pci,host=01:00.1 \
        -drive file=ubuntu-22.04.1-preinstalled-server-riscv64+unmatched.img,if=virtio,format=raw

The results:

U-Boot 2022.01+dfsg-2ubuntu2.3 (Nov 24 2022 - 19:40:06 +0000)

CPU:   rv64imafdch_zicbom_zicboz_zicsr_zifencei_zihintpause_zawrs_zca_zcd_zba_zbb_zbc_zbs_sstc_svadu
Model: riscv-virtio,qemu
DRAM:  Unhandled exception: Store/AMO access fault
EPC: 0000000080201738 RA: 0000000080210f20 TVAL: 00000000ff739f90

Code: b823 06b2 bc23 06b2 b023 08b2 b423 08b2 (b823 08b2)

resetting ...
System reset not supported on this platform
### ERROR ### Please RESET the board ###

Status

Updates

• A raw patch attached - https://lists.denx.de/pipermail/u-boot/2023-August/526606.html