ELF-based-loadmem | architectural restartable checkpoints

[jerryz123]

Misc:

• Fixes DMI-based SpikeTile bringup
• Switches to 2 memory channels in default config (this improves coverage of example configs)
• Fixes multi-channel DRAM model to not mmap more memory than needed

Loadmem:

• Loadmem now uses ELF files and fesvr's elfloader to perform memory initialization, instead of reading giant hex files. Generating giant plaintext hex files for large memory configs is slow and storage-intensive.
• legacy -hex targets are kept around, but are aliases of setting LOADMEM=1
• LOADMEM=1 is now the preferred way to use loadmem

Architectural checkpointing:

• Checkpoints can be generated from spike using scripts/generate-ckpt.sh
• Checkpoints can be reloaded into dmi-based configs with some flags

Ex: Run hello.riscv in spike for 100 cycles, generate checkpoint, then reload in dmiRocketConfig

cd sims/vcs
../../scripts/generate-ckpt.sh -b ../../tests/hello.riscv -c 100
make CONFIG=dmiRocketConfig run-binary LOADARCH=hello.riscv.0x80000000.100.loadarch

Related PRs / Issues:

Type of change:

• Bug fix
• New feature
• Other enhancement

Impact:

• RTL change
• Software change (RISC-V software)
• Build system change
• Other

Contributor Checklist:

• Did you set main as the base branch?
• Is this PR's title suitable for inclusion in the changelog and have you added a changelog:<topic> label?
• Did you state the type-of-change/impact?
• Did you delete any extraneous prints/debugging code?
• Did you mark the PR with a changelog: label?
• (If applicable) Did you update the conda .conda-lock.yml file if you updated the conda requirements file?
• (If applicable) Did you add documentation for the feature?
• (If applicable) Did you add a test demonstrating the PR?

• (If applicable) Did you mark the PR as Please Backport?

[abejgonzalez]

Generally, LGTM

[jerryz123]

As @tianrui-wei pointed out, cospike memory contents should be initialized to match SimDRAM. This necessitated fixing the SimDRAM multi-channel duplication bug as well.

[tianrui-wei]

LGTM, thanks for fixing dramsim related issues