On Tue, 12 Aug 2025 at 20:47, Vivian Wang <wangruik...@iscas.ac.cn> wrote: > > Hi, > > On QEMU 10.0.2 (NixOS unstable), U-Boot v2025.10-rc2 with > qemu-riscv64_smode_defconfig fails to boot a loaded kernel, with a > "Failed to reserve memory for fdt" error. Explicitly loading an FDT > seems to fix this, so this looks like a problem with reusing the boot FDT. > > My steps are: > > mkdir -p vmshare/extlinux > echo 'label 0' > vmshare/extlinux/extlinux.conf > echo ' linux /Image' >> vmshare/extlinux/extlinux.conf > cp .../Image vmshare/ # Grab a Linux kernel > qemu-system-riscv64 -m 1G -M virt -nographic -kernel u-boot.bin \ > -drive file=fat:ro:vmshare,format=raw,read-only=on > > Resulting in: > > Device 0: 1af4 VirtIO Block Device > Type: Hard Disk > Capacity: 504.0 MB = 0.4 GB (1032192 x 512) > ... is now current device > Scanning virtio 0:1... > Found /extlinux/extlinux.conf > Retrieving file: /extlinux/extlinux.conf > 1: 0 > Retrieving file: /Image > Moving Image from 0x84000000 to 0x80200000, end=0x81e88000 > ## Flattened Device Tree blob at bee8f640 > Booting using the fdt blob at 0xbee8f640 > Working FDT set to bee8f640 > Failed to reserve memory for fdt at 0xbee8f640 > FDT creation failed! hanging...### ERROR ### Please RESET the board ###
Looks like the FDT is part of the region reserved for U-boot image post relocation. That region is marked as no-overwrite, meaning any other allocation attempt to the region will fail. Please check the relevant log below. The relevant code is in boot/image-fdt.c:boot_relocate_fdt(). The code gets exercised because fdt_high and initrd_high are being set to all ones. This was working in 2025.07 simply because the function call's return value was not being checked. I am not sure why fdt_high and initrd_rd are being set to all ones. The documentation suggests that this is not a good thing. I removed this setting of fdt_high from include/configs/qemu-riscv.h, and with that the platform boots. Relevant boot log ----------------------- U-Boot 2025.10-rc2-dirty (Aug 13 2025 - 12:56:52 +0530) CPU: riscv Model: riscv-virtio,qemu DRAM: 1 GiB Core: 26 devices, 14 uclasses, devicetree: board Flash: 32 MiB Loading Environment from nowhere... OK In: serial,usbkbd Out: serial,vidconsole Err: serial,vidconsole No USB controllers found Net: No ethernet found. Working FDT set to beeb1ac0 Hit any key to stop autoboot: 0 => bdin boot_params = 0x0000000000000000 DRAM bank = 0x0000000000000000 -> start = 0x0000000080000000 -> size = 0x0000000040000000 flashstart = 0x0000000020000000 flashsize = 0x0000000002000000 flashoffset = 0x0000000000000000 baudrate = 115200 bps relocaddr = 0x00000000bf6d3000 reloc off = 0x000000003f4d3000 Build = 64-bit current eth = unknown eth-1addr = (not set) IP addr = <NULL> fdt_blob = 0x00000000beeb1ac0 lmb_dump_all: memory.count = 0x1 memory[0] [0x80000000-0xbfffffff], 0x40000000 bytes, flags: none reserved.count = 0x3 reserved[0] [0x80000000-0x8001ffff], 0x20000 bytes, flags: no-overwrite reserved[1] [0xbdeae000-0xbdeb0fff], 0x3000 bytes, flags: no-notify, no-overwrite reserved[2] [0xbdeb1ab0-0xbfffffff], 0x214e550 bytes, flags: no-overwrite <----- This is where the FDT resides. -sughosh > > (See bottom for full output including OpenSBI) > > The same steps succeeds with U-Boot 2025.07, so this appears to be a > regression. I haven't yet done a bisection or any (successful) > debugging, but this check seems to be added in [1]. > > Sughosh Ganu: This message seems to be added by [1]. Do you have any idea? > > Vivian "dramforever" Wang > > [1]: > https://lore.kernel.org/u-boot/20250617104346.1379981-1-sughosh.g...@linaro.org/ > > > Full log output: > > OpenSBI v1.5.1 > ____ _____ ____ _____ > / __ \ / ____| _ \_ _| > | | | |_ __ ___ _ __ | (___ | |_) || | > | | | | '_ \ / _ \ '_ \ \___ \| _ < | | > | |__| | |_) | __/ | | |____) | |_) || |_ > \____/| .__/ \___|_| |_|_____/|____/_____| > | | > |_| > > Platform Name : riscv-virtio,qemu > Platform Features : medeleg > Platform HART Count : 1 > Platform IPI Device : aclint-mswi > Platform Timer Device : aclint-mtimer @ 10000000Hz > Platform Console Device : uart8250 > Platform HSM Device : --- > Platform PMU Device : --- > Platform Reboot Device : syscon-reboot > Platform Shutdown Device : syscon-poweroff > Platform Suspend Device : --- > Platform CPPC Device : --- > Firmware Base : 0x80000000 > Firmware Size : 327 KB > Firmware RW Offset : 0x40000 > Firmware RW Size : 71 KB > Firmware Heap Offset : 0x49000 > Firmware Heap Size : 35 KB (total), 2 KB (reserved), 11 KB (used), 21 > KB (free) > Firmware Scratch Size : 4096 B (total), 416 B (used), 3680 B (free) > Runtime SBI Version : 2.0 > > Domain0 Name : root > Domain0 Boot HART : 0 > Domain0 HARTs : 0* > Domain0 Region00 : 0x0000000000100000-0x0000000000100fff M: (I,R,W) > S/U: (R,W) > Domain0 Region01 : 0x0000000010000000-0x0000000010000fff M: (I,R,W) > S/U: (R,W) > Domain0 Region02 : 0x0000000002000000-0x000000000200ffff M: (I,R,W) > S/U: () > Domain0 Region03 : 0x0000000080040000-0x000000008005ffff M: (R,W) > S/U: () > Domain0 Region04 : 0x0000000080000000-0x000000008003ffff M: (R,X) > S/U: () > Domain0 Region05 : 0x000000000c400000-0x000000000c5fffff M: (I,R,W) > S/U: (R,W) > Domain0 Region06 : 0x000000000c000000-0x000000000c3fffff M: (I,R,W) > S/U: (R,W) > Domain0 Region07 : 0x0000000000000000-0xffffffffffffffff M: () S/U: > (R,W,X) > Domain0 Next Address : 0x0000000080200000 > Domain0 Next Arg1 : 0x00000000bfe00000 > Domain0 Next Mode : S-mode > Domain0 SysReset : yes > Domain0 SysSuspend : yes > > Boot HART ID : 0 > Boot HART Domain : root > Boot HART Priv Version : v1.12 > Boot HART Base ISA : rv64imafdch > Boot HART ISA Extensions : sstc,zicntr,zihpm,zicboz,zicbom,sdtrig,svadu > Boot HART PMP Count : 16 > Boot HART PMP Granularity : 2 bits > Boot HART PMP Address Bits: 54 > Boot HART MHPM Info : 16 (0x0007fff8) > Boot HART Debug Triggers : 2 triggers > Boot HART MIDELEG : 0x0000000000001666 > Boot HART MEDELEG : 0x0000000000f0b509 > > > U-Boot 2025.10-rc2 (Jan 01 1980 - 00:00:00 +0000) > > CPU: riscv > Model: riscv-virtio,qemu > DRAM: 1 GiB > using memory 0xbee91000-0xbf6b1000 for malloc() > Core: 27 devices, 14 uclasses, devicetree: board > Flash: 32 MiB > Loading Environment from nowhere... OK > In: serial,usbkbd > Out: serial,vidconsole > Err: serial,vidconsole > No USB controllers found > Net: No ethernet found. > > Working FDT set to bee8f640 > Hit any key to stop autoboot: 0 > > Device 0: unknown device > > Device 0: 1af4 VirtIO Block Device > Type: Hard Disk > Capacity: 504.0 MB = 0.4 GB (1032192 x 512) > ... is now current device > Scanning virtio 0:1... > Found /extlinux/extlinux.conf > Retrieving file: /extlinux/extlinux.conf > 1: 0 > Retrieving file: /Image > Moving Image from 0x84000000 to 0x80200000, end=0x81e88000 > ## Flattened Device Tree blob at bee8f640 > Booting using the fdt blob at 0xbee8f640 > Working FDT set to bee8f640 > Failed to reserve memory for fdt at 0xbee8f640 > FDT creation failed! hanging...### ERROR ### Please RESET the board ### >
