riscv64 EDK 2 crashes in KVM based emulation

[Heinrich Schuchardt]

When running EDK2 as payload for QEMU using KVM a crash occurs in the VM:

$ qemu-system-riscv64 -M virt,acpi=off -accel kvm -m 4096 -nographic -drive if=pflash,format=raw,unit=0,file=RISCV_VIRT_CODE.fd,readonly=on -drive if=pflash,format=raw,unit=1,file=RISCV_VIRT_VARS.fd
!!!! RISCV64 Exception Type - 0000000000000002(EXCEPT_RISCV_ILLEGAL_INST) !!!!
     t0 = 0x00000000083FFFB28 t1 = 0x00000000083238BC8
     t2 = 0x00000000000000000 t3 = 0x00000000000000000
     t4 = 0x00000000000000000 t5 = 0x00000000000000000
     t6 = 0x00000000000000000 s0 = 0x00000000083FFFBC0
     s1 = 0x00000000000000000 s2 = 0x00000000000000000
     s3 = 0x00000000000000000 s4 = 0x00000000000000000
     s5 = 0x00000000000000000 s6 = 0x00000000000000000
     s7 = 0x00000000000000000 s8 = 0x00000000000000000
     s9 = 0x00000000000000000 s10 = 0x00000000000000000
    s11 = 0x00000000000000000 a0 = 0x0000000017E1DDD10
     a1 = 0x00000000000000021 a2 = 0x0000000017E1B1A80
     a3 = 0x00000000000000032 a4 = 0x00000000000000021
     a5 = 0x00000000000000021 a6 = 0x000000000832391E0
     a7 = 0x00000000083FFFA64 zero = 0x00000000000000000
     ra = 0x0000000017E0AFA08 sp = 0x00000000000000004
     gp = 0x00000000000000000 tp = 0x00000000000000000
   sepc = 0x0000000017E0B0824 sstatus = 0x00000000200000120
  stval = 0x000000000D20787D3
QEMU: Terminated

To reproduce the issue:

Run a Noble RISC-V virtual machine as described in https://wiki.ubuntu.com/RISC-V/QEMU.

sudo apt-get update
sudo apt-get install qemu-efi-riscv64 qemu-system-misc
cp /usr/share/qemu-efi-riscv64/RISCV_VIRT_*.fd .
qemu-system-riscv64 \
  -M virt,acpi=off -accel tcg -m 1024 \
  -nographic \
  -drive if=pflash,format=raw,unit=0,file=RISCV_VIRT_CODE.fd,readonly=on \
  -drive if=pflash,format=raw,unit=1,file=RISCV_VIRT_VARS.fd
# In the EFI shell
reset -s
sudo modprobe kvm
sudo qemu-system-riscv64 \
  -M virt,acpi=off -accel kvm -m 1024 \
  -nographic \
  -drive if=pflash,format=raw,unit=0,file=RISCV_VIRT_CODE.fd,readonly=on \
  -drive if=pflash,format=raw,unit=1,file=RISCV_VIRT_VARS.fd
# A crash occurs
# RISCV64 Exception Type - 0000000000000002(EXCEPT_RISCV_ILLEGAL_INST)
# Terminate emulation with <CTRL+A><x>

ProblemType: Bug
DistroRelease: Ubuntu 24.04
Package: qemu-efi-riscv64 2024.02-2
ProcVersionSignature: Ubuntu 6.8.0-31.31.1-generic 6.8.1
Uname: Linux 6.8.0-31-generic riscv64
ApportVersion: 2.28.1-0ubuntu2
Architecture: riscv64
CasperMD5CheckResult: unknown
CloudArchitecture: riscv64
CloudBuildName: server
CloudID: nocloud
CloudName: unknown
CloudPlatform: nocloud
CloudSerial: 20240423
CloudSubPlatform: seed-dir (/var/lib/cloud/seed/nocloud-net)
Date: Fri Aug 23 13:10:55 2024
Dependencies:

PackageArchitecture: all
ProcEnviron:
 LANG=C.UTF-8
 PATH=(custom, no user)
 SHELL=/bin/bash
 TERM=vt220
SourcePackage: edk2
UpgradeStatus: No upgrade log present (probably fresh install)

[Heinrich Schuchardt (xypron)]

The crash output is generated in EDK II, UefiCpuPkg/Library/BaseRiscV64CpuExceptionHandlerLib/CpuExceptionHandlerLib.c

Here we could add code showing the failing instruction. Only showing the registers is not helpful.

U-Boot creates output like:

Unhandled exception: Illegal instruction
EPC: 0000000087732eb0 RA: 000000008773c092 TVAL: 00000000ffffffff
EPC: 0000000080214eb0 RA: 000000008021e092 reloc adjusted

Code: f517 0006 0513 7305 b721 9002 4505 8082 (ffff ffff)

The last line can be disassembled with objcopy. See Linux' scripts/decodecode.

[Heinrich Schuchardt (xypron)]

The problem is reproducible with Ubuntu 24.10 running kernel 6.8.0-31-generic riscv64.