Add experimental Computational Storage Drive mode by Emilio597 · Pull Request #188 · MoatLab/FEMU

Emilio597 · 2026-05-26T08:32:15Z

Summary

This PR adds an experimental Computational Storage Drive (CSD) mode to FEMU as femu_mode=4.

The implementation is derived from CEMU, but adapted to FEMU's current codebase and configuration model. CSD-specific logic is kept under hw/femu/csd/ where possible, with only small hooks in common FEMU/NVMe paths.

This PR intentionally avoids requiring a CEMU-specific Linux kernel, FDMFS, or a fixed VM image.

What is included

Add femu_mode=4 for CSD mode
Add CSD QOM parameters:
- fdm_size
- nr_cu
- nr_thread
- time_slice
- context_switch_time
- csf_runtime_scale
Route normal CSD NVMe read/write through the BBSSD FTL path
Add AFDM operations:
- allocate/deallocate
- read/write
- NVM-to-AFDM copy
Add CEMU-style program lifecycle commands:
- load/unload
- activate/deactivate
Add shared-library CSF execution
Add optional uBPF support, disabled by default:
- ./femu-compile.sh --enable-csd-ubpf
- ./femu-compile.sh --enable-csd-ubpf=/path/to/ubpf-cemu
Add Memory Range Set management using the NVMe Computational Programs command set style:
- MRS create/delete
- RSID returned through CQE Dword 0 for create
Add guest-side passthrough tests under tests/femu-csd/
Add run-csd.sh following FEMU script style

What is intentionally not included

Kernel-side FDMFS and CEMU-specific guest kernel changes
VM freezing / virtual clock changes
multi-CSD/P2P experiments

Validation

Build/static checks:

./femu-compile.sh
ninja -C build-femu qemu-system-x86_64
make -C tests/femu-csd

Manual KVM guest end-to-end validation can be reproduced with a normal Linux guest image. No CEMU-specific kernel, FDMFS, or fixed VM image is required.

Start a CSD VM:

cd build-femu
./run-csd.sh

Copy the passthrough tests into the guest and build them there:

cd tests/femu-csd
make
scp -P 8080 -r . root@localhost:/root/femu-csd
ssh -p 8080 root@localhost
cd /root/femu-csd
make clean && make

Run the core CSD command smoke tests:

./csd-passthru /dev/nvme0n1 smoke
./csd-passthru /dev/nvme0n1 smoke-so /home/<user>/FEMU/tests/femu-csd/csd-vadd.so
./csd-passthru /dev/nvme0n1 smoke-so-all /home/<user>/FEMU/tests/femu-csd/csd-original-kernels.so
./csd-passthru /dev/nvme0n1 smoke-mrs /home/<user>/FEMU/tests/femu-csd/csd-vadd.so
./csd-passthru /dev/nvme0n1 vadd-example /home/<user>/FEMU/tests/femu-csd/csd-vadd.so
./csd-passthru /dev/nvme0n1 sync-breakdown /home/<user>/FEMU/tests/femu-csd/csd-vadd.so 4096 16
./csd-passthru /dev/nvme0n1 indirect-vadd /home/<user>/FEMU/tests/femu-csd/csd-vadd.so
./csd-passthru /dev/nvme0n1 benchmark-kernels /home/<user>/FEMU/tests/femu-csd/csd-vadd.so /home/<user>/FEMU/tests/femu-csd/csd-original-kernels.so 1
./csd-passthru /dev/nvme0n1 bench 4096 32
./csd-passthru /dev/nvme0n1 bench 65536 16

Optional uBPF validation requires building FEMU with uBPF support:

./femu-compile.sh --enable-csd-ubpf=/path/to/ubpf-cemu
cd tests/femu-csd
make bpf

Then, inside the guest:

./csd-passthru /dev/nvme0n1 smoke-ubpf /home/<user>/FEMU/tests/femu-csd/csd-vadd.bpf.o 0
./csd-passthru /dev/nvme0n1 smoke-ubpf /home/<user>/FEMU/tests/femu-csd/csd-vadd.bpf.o 1

The KVM guest end-to-end validation covered:

AFDM smoke
shared-library CSF execution
original CEMU-style kernels: vadd, knn, sql, grep, lz4
FDMFS-free MRS create/delete and execute by RSID
NVM-to-AFDM copy
sync breakdown: NVM-to-AFDM, exec, AFDM read
indirect vadd smoke
compact benchmark smoke
optional uBPF interpreter/JIT path when built with uBPF support

Copilot

Pull request overview

This PR introduces an experimental Computational Storage Drive (CSD) mode (femu_mode=4) to FEMU, including host-side computational program lifecycle handling and guest-side passthrough tooling to exercise the new vendor/admin commands without requiring a CEMU-specific kernel/FDMFS setup.

Changes:

Add a new FEMU controller mode (femu_mode=4) with CSD-specific NVMe admin/I/O command handling under hw/femu/csd/.
Add build/config plumbing for optional uBPF support (Meson option + femu-compile.sh flag) and a run-csd.sh launcher script.
Add guest-side passthrough tests and sample kernels under tests/femu-csd/, plus README documentation updates.

Reviewed changes

Copilot reviewed 22 out of 22 changed files in this pull request and generated 10 comments.

Show a summary per file

File	Description
`tests/femu-csd/README.md`	Documents guest-side passthrough tests and how to run CSD validations.
`tests/femu-csd/Makefile`	Builds passthrough tool and sample shared-library/BPF kernels.
`tests/femu-csd/femu-csd-kernel.h`	Defines the shared CSD kernel ABI struct used by sample kernels.
`tests/femu-csd/csd-vadd.c`	Sample shared-library kernels (direct + indirect vadd).
`tests/femu-csd/csd-vadd.bpf.c`	Sample uBPF kernel.
`tests/femu-csd/csd-passthru.c`	Guest-side NVMe passthrough tool exercising CSD admin/I/O commands.
`tests/femu-csd/csd-original-kernels.cc`	Ports of selected original CEMU kernels into a shared library.
`scripts/meson-buildoptions.sh`	Adds configure-wrapper options for enabling/disabling FEMU CSD uBPF.
`README.md`	Adds CSD mode documentation and updates the feature table and tree.
`meson.build`	Adds Meson options/deps wiring for optional uBPF support.
`meson_options.txt`	Introduces `femu_csd_ubpf` and `femu_csd_ubpf_path` options.
`hw/femu/nvme.h`	Adds CSD controller params, mode constant, and `admin_cmd_cqe` hook.
`hw/femu/nvme-io.c`	Treats CSD like BBSSD/ZNSSD in CQ completion processing path selection.
`hw/femu/nvme-admin.c`	Routes unknown admin opcodes to `ext_ops.admin_cmd_cqe()` when present.
`hw/femu/meson.build`	Builds and links `csd/csd.c` and wires in optional uBPF dep.
`hw/femu/femu.c`	Registers the CSD extension and adds QOM properties for CSD params.
`hw/femu/csd/csd.h`	Adds CSD command structs and private definitions.
`hw/femu/csd/csd.c`	Implements CSD mode: AFDM, MRS, program load/activate, exec, QoS groups, optional uBPF.
`hw/femu/backend/dram.c`	Treats CSD like BBSSD/ZNSSD/NoSSD for DRAM backend addressing logic.
`femu-scripts/run-csd.sh`	New script to run a CSD-configured VM.
`femu-scripts/femu-copy-scripts.sh`	Copies `run-csd.sh` alongside other FEMU helper scripts.
`femu-scripts/femu-compile.sh`	Adds `--enable-csd-ubpf[...]` configuration support.

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+    FemuCsdState *csd = csd_state(n);
+    NvmeCsdProgramActivationCmd *activation =
+        (NvmeCsdProgramActivationCmd *)cmd;
+    uint16_t pind = activation->pind;
+    uint8_t sel = activation->sel;
+    FemuCsdProgram *program;


+        qemu_mutex_lock(&csd->lock);
+        id = csd->next_rsid++;
+        if (id == 0) {
+            csd->next_rsid = 1;
+            id = csd->next_rsid++;
+        }
+        while (g_hash_table_contains(csd->mrs, GUINT_TO_POINTER(id))) {
+            id = csd->next_rsid++;
+            if (id == 0) {
+                csd->next_rsid = 1;
+                id = csd->next_rsid++;
+            }
+        }


+    qemu_mutex_lock(&csd->lock);
+    id = csd->next_group_id++;
+    if (id == 0) {
+        csd->next_group_id = 1;
+        id = csd->next_group_id++;
+    }
+    group->id = id;
+    g_hash_table_insert(csd->groups, GUINT_TO_POINTER(id), group);
+    qemu_mutex_unlock(&csd->lock);


+    if (runtime) {
+        req->reqlat += runtime;
+        req->expire_time += runtime;
+    }


+    if (!status) {
+        req->cqe.n.result = result > UINT32_MAX ? UINT32_MAX : result;
+    }


+    program->module = g_module_open(path, G_MODULE_BIND_LOCAL);
+    if (!program->module) {
+        femu_err("CSD: failed to load shared library %s: %s\n", path,
+                 g_module_error());
+        return NVME_INVALID_FIELD | NVME_DNR;
+    }
+
+    if (!g_module_symbol(program->module, symbol, &fn) || !fn) {
+        femu_err("CSD: failed to find shared library symbol %s: %s\n", symbol,
+                 g_module_error());
+        csd_program_unload(program);
+        return NVME_INVALID_FIELD | NVME_DNR;
+    }
+
+    program->shared_lib_fn = (FemuCsdSharedLibFn)fn;
+    return NVME_SUCCESS;


+    if (pind == 0 || psize > UINT32_MAX || loff > psize ||
+        numb > psize - loff) {
+        return NVME_INVALID_FIELD | NVME_DNR;
+    }


+if femu_csd_ubpf_path != ''
+  femu_csd_ubpf_lib_path = femu_csd_ubpf_path / 'build/lib/libubpf.a'
+  femu_csd_ubpf_lib = cc.find_library('ubpf',
+                                      dirs: femu_csd_ubpf_path / 'build/lib',
+                                      required: get_option('femu_csd_ubpf'))
+  femu_csd_ubpf = declare_dependency(
+    include_directories: include_directories(femu_csd_ubpf_path / 'vm/inc',
+                                             femu_csd_ubpf_path / 'build/vm'),
+    dependencies: femu_csd_ubpf_lib)
+  emulator_link_args += femu_csd_ubpf_lib_path


+                             'bbssd/bb.c', 'bbssd/ftl.c', 'csd/csd.c',
+                             'lib/pqueue.c', 'lib/rte_ring.c',
+                             'backend/dram.c'))
+system_ss.add(when: 'CONFIG_FEMU_CSD_UBPF', if_true: femu_csd_ubpf)


+        --enable-csd-ubpf=*)
+            UBPF_PATH="${arg#*=}"
+            FEMU_CONFIGURE_OPTS="${FEMU_CONFIGURE_OPTS} --enable-femu-csd-ubpf -Dfemu_csd_ubpf_path=${UBPF_PATH}"
+            ;;


huaicheng · 2026-05-28T16:47:47Z

CSD emulation is a great addition to FEMU, and CEMU is a very nice work, thank you for upstreaming it!

Emilio597 added 10 commits May 25, 2026 11:35

hw/femu: add experimental CSD mode

7f585cb

tests/femu-csd: add CSD passthrough tests and run script

92b38a0

hw/femu: add CSD shared library execution

7181c40

hw/femu: route CSD I/O through SSD FTL

0d9b3f4

hw/femu: add CSD program lifecycle commands

2bfc150

hw/femu: use CSD program lifecycle for tests

0a684d6

hw/femu: check CSD NVM copy against FTL map

be56d81

tests/femu-csd: expand shared library and latency coverage

a0a9735

tests/femu-csd: add optional ubpf and lz4 coverage

afdefcc

hw/femu: add CSD MRS and passthrough examples

838e53e

huaicheng requested review from Copilot, huaicheng and wangyuyue May 27, 2026 05:45

Copilot started reviewing on behalf of huaicheng May 28, 2026 16:20 View session

Copilot AI reviewed May 28, 2026

View reviewed changes

huaicheng merged commit eb01bb7 into MoatLab:master May 28, 2026
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Add experimental Computational Storage Drive mode#188

Add experimental Computational Storage Drive mode#188
huaicheng merged 10 commits into
MoatLab:masterfrom
Emilio597:cemu-csd-minimal

Emilio597 commented May 26, 2026 •

edited

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Emilio597 commented May 26, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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Summary

What is included

What is intentionally not included

Validation

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Pull request overview

Reviewed changes

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huaicheng commented May 28, 2026

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Emilio597 commented May 26, 2026 •

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