On Thu, Jul 7, 2022 at 10:19 AM Bin Meng <bmeng.cn@xxxxxxxxx> wrote: > > Hi Anup, > > U-Boot S-mode payload does not boot with RISC-V KVM on the QEMU 'virt' > multicore machine. With QEMU TCG it can boot. > > I am using the latest v5.19-rc5 kernel, along with QEMU 7.0.0 and > U-Boot v2022.04: > > Reproduce steps: > > U-Boot S-mode payload is built from U-Boot v2022.04: > $ make qemu-riscv64_smode_defconfig; make > > The host 5.19-rc5 kernel is running on top of QEMU 7.0.0 on an x86 machine. > > Use QEMU to launch the VM: > # qemu-system-riscv64 -M virt -accel kvm -m 2G -smp 2 -nographic > -kernel u-boot -device virtio-net-device,netdev=eth0 -netdev > user,id=eth0,hostfwd=tcp::8022-:22 > > U-Boot gets stuck during boot, logs below: > > U-Boot 2022.04 (Jul 07 2022 - 11:23:28 +0800) > CPU: rv64imafdc > Model: riscv-virtio,qemu > DRAM: 2 GiB > Core: 17 devices, 9 uclasses, devicetree: board > Flash: <========== stuck here, and QEMU is completely unresponsive > (Ctrl+A, C is ignored) > > The kernel reports: > > [ 484.351698] INFO: task qemu-system-ris:1765 blocked for more than 120 seconds. > [ 484.360285] Not tainted 5.19.0-rc5-custom #1 > [ 484.360871] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" > disables this message. > [ 484.362560] task:qemu-system-ris state:D stack: 0 pid: 1765 ppid: > 1515 flags:0x00000000 > [ 484.363785] Call Trace: > [ 484.363930] [] schedule+0x50/0xb2 > [ 484.364758] [] schedule_timeout+0x10c/0x13c > [ 484.364806] [] __wait_for_common+0x148/0x226 > [ 484.364840] [] wait_for_completion+0x2e/0x36 > [ 484.364871] [] __synchronize_srcu.part.0+0x88/0xe2 > [ 484.364918] [] synchronize_srcu_expedited+0x3a/0x44 > [ 484.364952] [] kvm_swap_active_memslots+0x186/0x1ea > [ 484.364985] [] kvm_set_memslot+0x1fc/0x39c > [ 484.365014] [] __kvm_set_memory_region+0x144/0x30c > [ 484.365043] [] kvm_vm_ioctl+0x20a/0xc82 > [ 484.365075] [] sys_ioctl+0x98/0xb2 > [ 484.365135] [] ret_from_syscall+0x0/0x2 > > The QEMU vcpu thread backtrace is: > > #0 __GI___ioctl (fd=, request=request@entry=1075883590) at > ../sysdeps/unix/sysv/linux/ioctl.c:35 > #1 0x00aaaaaab8b916ae in kvm_vm_ioctl (s=s@entry=0xaaaaaaf1ec3e00, > type=type@entry=1075883590) at ../accel/kvm/kvm-all.c:3035 > #2 0x00aaaaaab8b93572 in kvm_set_user_memory_region > (slot=slot@entry=0xffffffaa5d90a0, new=new@entry=false, > kml=0xaaaaaaf1ec4eb0, kml=) at ../accel/kvm/kvm-all.c:379 > #3 0x00aaaaaab8b93862 in kvm_set_phys_mem (kml=0xaaaaaaf1ec4eb0, > section=section@entry=0xffffffaa513b70, add=, add@entry=false) at > ../accel/kvm/kvm-all.c:1413 > #4 0x00aaaaaab8b93a30 in kvm_region_del (listener=, > section=0xffffffaa513b70) at ../accel/kvm/kvm-all.c:1511 > #5 0x00aaaaaab8ad780c in address_space_update_topology_pass > (as=as@entry=0xaaaaaab90b87a0 , > old_view=old_view@entry=0xaaaaaaf1f42c40, > new_view=new_view@entry=0xffffff1c001400, adding=adding@entry=fa > lse) at ../softmmu/memory.c:948 > #6 0x00aaaaaab8ad7a2a in address_space_set_flatview > (as=0xaaaaaab90b87a0 ) at ../softmmu/memory.c:1050 > #7 0x00aaaaaab8ada508 in memory_region_transaction_commit () at > ../softmmu/memory.c:1103 > #8 0x00aaaaaab8adb6ee in memory_region_rom_device_set_romd > (mr=mr@entry=0xaaaaaaf22d6fe0, romd_mode=romd_mode@entry=false) at > ../softmmu/memory.c:2289 > #9 0x00aaaaaab8951e1a in pflash_write (be=0, width=1, value=240, > offset=0, pfl=0xaaaaaaf22d6c30) at ../hw/block/pflash_cfi01.c:451 > #10 pflash_mem_write_with_attrs (opaque=0xaaaaaaf22d6c30, addr=0, > value=, len=, attrs=...) at ../hw/block/pflash_cfi01.c:682 > #11 0x00aaaaaab8ad5fa2 in access_with_adjusted_size > (addr=addr@entry=0, value=value@entry=0xffffffaa513dc8, > size=size@entry=1, access_size_min=, access_size_max=, > access_fn=0xaaaaaab8ad7d06 < > memory_region_write_with_attrs_accessor>, mr=0xaaaaaaf22d6fe0, > attrs=...) at ../softmmu/memory.c:554 > #12 0x00aaaaaab8ad92ba in memory_region_dispatch_write > (mr=mr@entry=0xaaaaaaf22d6fe0, addr=addr@entry=0, data=, > data@entry=240, op=, attrs=attrs@entry=...) at > ../softmmu/memory.c:1521 > #13 0x00aaaaaab8adee88 in flatview_write_continue > (fv=fv@entry=0xaaaaaaf1f42c40, addr=addr@entry=536870912, > attrs=attrs@entry=..., ptr=ptr@entry=0xffffffab730028, > len=len@entry=1, addr1=, l=, > mr=0xaaaaaaf22d6fe0) at ../softmmu/physmem.c:2814 > #14 0x00aaaaaab8adf0d8 in flatview_write (fv=0xaaaaaaf1f42c40, > addr=536870912, attrs=..., buf=0xffffffab730028, len=len@entry=1) at > ../softmmu/physmem.c:2856 > #15 0x00aaaaaab8ae1eca in address_space_write (len=1, > buf=0xffffffab730028, attrs=..., addr=536870912, as=0xaaaaaab90b87a0 ) > at ../softmmu/physmem.c:2952 > #16 address_space_rw (as=0xaaaaaab90b87a0 , addr=536870912, attrs=..., > attrs@entry=..., buf=buf@entry=0xffffffab730028, len=1, is_write=) at > ../softmmu/physmem.c:2962 > #17 0x00aaaaaab8b94a3e in kvm_cpu_exec > (cpu=cpu@entry=0xaaaaaaf1ec92f0) at ../accel/kvm/kvm-all.c:2929 > #18 0x00aaaaaab8b95572 in kvm_vcpu_thread_fn > (arg=arg@entry=0xaaaaaaf1ec92f0) at ../accel/kvm/kvm-accel-ops.c:49 > #19 0x00aaaaaab8ca280a in qemu_thread_start (args=) at > ../util/qemu-thread-posix.c:556 > #20 0x00ffffffab2cf5a6 in start_thread (arg=) at ./nptl/pthread_create.c:442 > #21 0x00ffffffab31ba02 in __thread_start () at > ../sysdeps/unix/sysv/linux/riscv/clone.S:85 > > Based on above 2 logs, we can see the QEMU vcpu thread is blocked at KVM ioctl > KVM_SET_USER_MEMORY_REGION, and on the kernel side the ioctl call is > blocked at synchronize_srcu_expedited() so that ioctl never returns > back to the user land. > > If I single step the QEMU instance starting from a breakpoint at > pflash_write(), the ioctl call of KVM_SET_USER_MEMORY_REGION does not > block, and U-Boot can boot eventually. > > If I remove "-smp 2" from the QEMU command line when launching the VM, > U-Boot boots without any problem. Of course removing "-accel kvm" > works too. > > It looks to me there is a locking timing issue in the RISC-V KVM > kernel when an SMP guest is launched. Any ideas? To further isolate the problem, does it work if QEMU does not generate the pflash DT node ? Regards, Anup
