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envelope-from=uverma@linux.ibm.com; helo=mx0b-001b2d01.pphosted.com X-Spam_score_int: -26 X-Spam_score: -2.7 X-Spam_bar: -- X-Spam_report: (-2.7 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: qemu development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org + Alexey (AMD) Hi Alexey, Will you continue to maintain VOF in QEMU? Could you please share your feedback on this patch series? Regards, Utkarsh On 8/17/26 3:57 PM, uverma@linux.ibm.com wrote: > From: Utkarsh Verma > > This series adds support for booting from a disk image under the Virtual Open > Firmware (VOF) path for sPAPR/pseries machines in QEMU. > > The most common use case for pseries VMs is booting from a distro qcow2 disk > image. These images carry a PReP boot partition containing GRUB2, which in turn > loads the kernel and initrd via IEEE 1275 client interface calls. > VOF currently only supports direct -kernel/-initrd boot; there is no > firmware-mediated path to hand off to a bootloader on disk. This series > implements that missing path, making VOF capable of handling the standard > distro qcow2 boot flow without requiring SLOF. > > This series takes reference from an earlier implementation by Alexey > Kardashevskiy [1] which explored the same concept but was not carried forward at > the time. > > The existing load_elf function works on a file, whereas in the VOF the PReP > partition (GRUB) is read from the disk image and loaded in the memory, also > on loading the PReP partition in the guest memory the /memory@0/available FDT > needs to be properly updated for each PT_LOAD segment of the core.elf file > of the GRUB (PReP partition). > > Implemented a new public elf loader API load_elf_ram_sym_buf() to resolve both > these issues. load_elf_ram_sym_buf() accepts a caller-supplied memory buffer > instead of a filename. Internally it writes the buffer to an anonymous memfd > and delegates to the existing load_elf32/load_elf64 paths, so all existing > behaviour is preserved. Also, added optional segment_fn_t callback in > load_elf_ram_sym_buf() through the internal elf_ops.h.inc template; it is > invoked once per PT_LOAD segment after the load address is resolved, allowing > callers to perform per-segment work such as VOF memory claims. > > When no -kernel is given, spapr_vof_reset() calls a newly implemented function > spapr_vof_try_prep_boot() which iterates attached block backends, scans > partitions for a PReP boot partition, reads the partition contents into a > host buffer, calls load_elf_ram_sym_buf() to load the GRUB in the guest memory, > and on success stores the ELF entry point in spapr->kernel_addr. > spapr_vof_client_dt_finalize() then writes the entry point into > /chosen/qemu,boot-kernel so VOF then transfers control to GRUB. > > - Partition scanner (spapr_vof_partition.c): scans MBR and GPT partition tables > on a BlockBackend to locate the PReP boot partition. > > - Core loader extension (hw/core/loader.c): new load_elf_ram_sym_buf() API loads > a 32/64-bit ELF binary from a caller-supplied memory buffer, reusing the > existing load_elf32/load_elf64 paths via a memfd. A new segment_fn_t callback > in elf_ops.h.inc lets callers act on each PT_LOAD segment as it is resolved. > > - read, seek OF services: two previously unimplemented IEEE 1275 client > services, covering block device I/O needed by GRUB. > > - vscsi-report-luns method: walks the SCSIBus and builds the LUN report table > in guest memory in the format expected by GRUB's ofdisk driver, matching > SLOF's dev-generate-srplun encoding. > > - VTY write/read routing: routes console I/O through the VTY chardev backend; > promotes vty_getchars to external linkage. > > - FDT disk@ child nodes (spapr_vscsi.c): emits a child FDT node per > attached SCSI disk in VOF mode, giving GRUB a fully-qualified OF path to open. > Gated on spapr->vof so SLOF boots are unaffected. > > We used AI to build prototype with manual changes incorporated as identified > during debugging multiple issues faced while making it work, hence using below > tag as suggested in [2]. > AI-used-for: Code > > Testing: > > The series has been tested end-to-end by booting a RHEL9.7 qcow2 image on a > pseries machine with VOF enabled (no SLOF). > > build$ ./qemu-system-ppc64 -M pseries,x-vof=on -cpu power9 -m 2G \ > -hda ../../rhel-guest-image-9.7-20251021.0.ppc64le.qcow2 -nographic > qemu-system-ppc64: warning: TCG doesn't support requested feature, cap-cfpc=workaround > qemu-system-ppc64: warning: TCG doesn't support requested feature, cap-ibs=workaround > qemu-system-ppc64: warning: TCG doesn't support requested feature, cap-ccf-assist=on > Welcome to GRUB! > > GRUB version 2.06 > > +----------------------------------------------------------------------------+ > |*Red Hat Enterprise Linux (5.14.0-611.5.1.el9_7.ppc64le) 9.7 (Plow) | > | | > | | > | | > | | > | | > | | > | | > | | > | | > | | > | | > +----------------------------------------------------------------------------+ > > Use the ^ and v keys to select which entry is highlighted. > Press enter to boot the selected OS, `e' to edit the commands > before booting or `c' for a command-line. > > > > Red Hat Enterprise Linux 9.7 (Plow) > Kernel 5.14.0-611.5.1.el9_7.ppc64le on an ppc64le > > Activate the web console with: systemctl enable --now cockpit.socket > > localhost login: root > Password: > Last login: Fri Jul 10 01:45:44 on hvc0 > [root@localhost ~]# > [root@localhost ~]# ls / > afs boot etc lib media opt root sbin sys usr > bin dev home lib64 mnt proc run srv tmp var > [root@localhost ~]# > [root@localhost ~]# echo "Hello, World!" > hello.txt > [root@localhost ~]# cat hello.txt > Hello, World! > [root@localhost ~]# > > [1] https://lore.kernel.org/qemu-devel/20200203032943.121178-1-aik@ozlabs.ru/#t > [2] https://lore.kernel.org/qemu-devel/20260529094619.1034458-1-pbonzini@redhat.com/ > > Utkarsh Verma (8): > ppc/spapr: add PReP boot partition detection > hw/loader: add load_elf_ram_sym_buf() for in-memory ELF loading > ppc/spapr: add baseline VOF disk boot support > ppc/spapr: add VTY backend support to OF read/write/open services > ppc/spapr: add block device backend to VOF open/read/write/seek > services > spapr_vscsi: add VOF disk nodes to the device tree > ppc/spapr: strip OF path argument suffix in path_offset > ppc/spapr: implement vscsi-report-luns call-method for PAPR vSCSI > > hw/char/spapr_vty.c | 2 +- > hw/core/loader.c | 77 ++++++- > hw/ppc/meson.build | 5 +- > hw/ppc/spapr_vof.c | 144 +++++++++++- > hw/ppc/spapr_vof_partition.c | 176 ++++++++++++++ > hw/ppc/trace-events | 4 + > hw/ppc/vof.c | 429 +++++++++++++++++++++++++++++++++++ > hw/scsi/spapr_vscsi.c | 40 ++++ > include/hw/core/loader.h | 30 +++ > include/hw/elf_ops.h.inc | 12 +- > include/hw/ppc/spapr_vio.h | 1 + > include/hw/ppc/spapr_vof.h | 14 ++ > include/hw/ppc/vof.h | 2 + > 13 files changed, 923 insertions(+), 13 deletions(-) > create mode 100644 hw/ppc/spapr_vof_partition.c > create mode 100644 include/hw/ppc/spapr_vof.h >