Re: virtio,iommu_platform=on

[Alexey Kardashevskiy]

On 12/11/2019 20:06, Laszlo Ersek wrote:
> On 11/12/19 04:53, Alexey Kardashevskiy wrote:
>> Hi!
>>
>> I am enabling IOMMU for virtio in the pseries firmware (SLOF) and seeing
>> problems, one of them is SLOF does SCSI bus scan, then it stops the
>> virtio-scsi by clearing MMIO|IO|BUSMASTER from PCI_COMMAND (as SLOF
>> stopped using the devices) and when this happens, I see unassigned
>> memory access (see below) which happens because disabling busmaster
>> disables IOMMU and QEMU cannot access the rings to do some shutdown. And
>> when this happens, the device does not come back even if SLOF re-enables it.
>>
>> Hacking SLOF to not clear BUSMASTER makes virtio-scsi work but it is
>> hardly a right fix.
>>
>> Is this something expected? Thanks,
> 
> Can you perform a virtio reset (write 0 to the virtio-scsi-pci device's
> virtio status register) in SLOF, before clearing PCI_COMMAND?


The device stops working in SLOF, even if I do not remove bus master bit
ever. Weird...


> 
> Thanks,
> Laszlo
> 
> 
>>
>>
>> Here is the exact command line:
>>
>> /home/aik/pbuild/qemu-garrison2-ppc64/ppc64-softmmu/qemu-system-ppc64 \
>>
>> -nodefaults \
>>
>> -chardev stdio,id=STDIO0,signal=off,mux=on \
>>
>> -device spapr-vty,id=svty0,reg=0x71000110,chardev=STDIO0 \
>>
>> -mon id=MON0,chardev=STDIO0,mode=readline \
>>
>> -nographic \
>>
>> -vga none \
>>
>> -enable-kvm \
>> -m 2G \
>>
>> -device
>> virtio-scsi-pci,id=vscsi0,iommu_platform=on,disable-modern=off,disable-legacy=on
>> \
>> -drive id=DRIVE0,if=none,file=img/u1804-64le.qcow2,format=qcow2 \
>>
>> -device scsi-disk,id=scsi-disk0,drive=DRIVE0 \
>>
>> -snapshot \
>>
>> -smp 1 \
>>
>> -machine pseries \
>>
>> -L /home/aik/t/qemu-ppc64-bios/ \
>>
>> -trace events=qemu_trace_events \
>>
>> -d guest_errors \
>>
>> -chardev socket,id=SOCKET0,server,nowait,path=qemu.mon.ssh59518 \
>>
>> -mon chardev=SOCKET0,mode=control
>>
>>
>>
>> Here is the backtrace:
>>
>> Thread 5 "qemu-system-ppc" hit Breakpoint 8, unassigned_mem_accepts
>> (opaque=0x0, addr=0x5802, size=0x2, is_write=0x0, attrs=...) at /home/
>> aik/p/qemu/memory.c:1275
>> 1275        return false;
>> #0  unassigned_mem_accepts (opaque=0x0, addr=0x5802, size=0x2,
>> is_write=0x0, attrs=...) at /home/aik/p/qemu/memory.c:1275
>> #1  0x00000000100a8ac8 in memory_region_access_valid (mr=0x1105c230
>> <io_mem_unassigned>, addr=0x5802, size=0x2, is_write=0x0, attrs=...) at
>> /home/aik/p/qemu/memory.c:1377
>> #2  0x00000000100a8c88 in memory_region_dispatch_read (mr=0x1105c230
>> <io_mem_unassigned>, addr=0x5802, pval=0x7ffff550d410, op=MO_16,
>> attrs=...) at /home/aik/p/qemu/memory.c:1418
>> #3  0x000000001001cad4 in address_space_lduw_internal_cached_slow
>> (cache=0x7fff68036fa0, addr=0x2, attrs=..., result=0x0,
>> endian=DEVICE_LITTLE_ENDIAN) at /home/aik/p/qemu/memory_ldst.inc.c:211
>> #4  0x000000001001cc84 in address_space_lduw_le_cached_slow
>> (cache=0x7fff68036fa0, addr=0x2, attrs=..., result=0x0) at
>> /home/aik/p/qemu/memory_ldst.inc.c:249
>> #5  0x000000001019bd80 in address_space_lduw_le_cached
>> (cache=0x7fff68036fa0, addr=0x2, attrs=..., result=0x0) at
>> /home/aik/p/qemu/include/exec/memory_ldst_cached.inc.h:56
>> #6  0x000000001019c10c in lduw_le_phys_cached (cache=0x7fff68036fa0,
>> addr=0x2) at /home/aik/p/qemu/include/exec/memory_ldst_phys.inc.h:91
>> #7  0x000000001019d86c in virtio_lduw_phys_cached (vdev=0x118b9110,
>> cache=0x7fff68036fa0, pa=0x2) at
>> /home/aik/p/qemu/include/hw/virtio/virtio-access.h:166
>> #8  0x000000001019e648 in vring_avail_idx (vq=0x118c2720) at
>> /home/aik/p/qemu/hw/virtio/virtio.c:302
>> #9  0x000000001019f5bc in virtio_queue_split_empty (vq=0x118c2720) at
>> /home/aik/p/qemu/hw/virtio/virtio.c:581
>> #10 0x000000001019f838 in virtio_queue_empty (vq=0x118c2720) at
>> /home/aik/p/qemu/hw/virtio/virtio.c:612
>> #11 0x00000000101a8fa8 in virtio_queue_host_notifier_aio_poll
>> (opaque=0x118c2798) at /home/aik/p/qemu/hw/virtio/virtio.c:3389
>> #12 0x000000001092679c in run_poll_handlers_once (ctx=0x11212e40,
>> timeout=0x7ffff550d7d8) at /home/aik/p/qemu/util/aio-posix.c:520
>> #13 0x0000000010926aec in try_poll_mode (ctx=0x11212e40,
>> timeout=0x7ffff550d7d8) at /home/aik/p/qemu/util/aio-posix.c:607
>> #14 0x0000000010926c2c in aio_poll (ctx=0x11212e40, blocking=0x1) at
>> /home/aik/p/qemu/util/aio-posix.c:639
>> #15 0x000000001091fe0c in aio_wait_bh_oneshot (ctx=0x11212e40,
>> cb=0x1016f35c <virtio_scsi_dataplane_stop_bh>, opaque=0x118b9110) at
>> /home/aik/p/qemu/util/aio-wait.c:71
>> #16 0x000000001016fa60 in virtio_scsi_dataplane_stop (vdev=0x118b9110)
>> at /home/aik/p/qemu/hw/scsi/virtio-scsi-dataplane.c:211
>> #17 0x0000000010684740 in virtio_bus_stop_ioeventfd (bus=0x118b9098) at
>> /home/aik/p/qemu/hw/virtio/virtio-bus.c:245
>> #18 0x0000000010688290 in virtio_pci_stop_ioeventfd (proxy=0x118b0fa0)
>> at /home/aik/p/qemu/hw/virtio/virtio-pci.c:292
>> #19 0x00000000106891e8 in virtio_write_config (pci_dev=0x118b0fa0,
>> address=0x4, val=0x100100, len=0x4) at
>> /home/aik/p/qemu/hw/virtio/virtio-pci.c:613
>> #20 0x00000000105b7228 in pci_host_config_write_common
>> (pci_dev=0x118b0fa0, addr=0x4, limit=0x100, val=0x100100, len=0x4) at
>> /home/aik/p/qemu/hw/pci/pci_host.c:81
>> #21 0x00000000101f7bdc in finish_write_pci_config (spapr=0x11217200,
>> buid=0x800000020000000, addr=0x4, size=0x4, val=0x100100,
>> rets=0x7e7533e0) at /home/aik/p/qemu/hw/ppc/spapr_pci.c:192
>> #22 0x00000000101f7cec in rtas_ibm_write_pci_config (cpu=0x11540df0,
>> spapr=0x11217200, token=0x2017, nargs=0x5, args=0x7e7533cc, nret=0x1,
>> rets=0x7e7533e0) at /home/aik/p/qemu/hw/ppc/spapr_pci.c:216
>> #23 0x00000000101f5860 in spapr_rtas_call (cpu=0x11540df0,
>> spapr=0x11217200, token=0x2017, nargs=0x5, args=0x7e7533cc, nret=0x1,
>> rets=0x7e7533e0) at /home/aik/p/qemu/hw/ppc/spapr_rtas.c:416
>> #24 0x00000000101ee214 in h_rtas (cpu=0x11540df0, spapr=0x11217200,
>> opcode=0xf000, args=0x7ffff4cf0030) at
>> /home/aik/p/qemu/hw/ppc/spapr_hcall.c:1214
>> #25 0x00000000101f0524 in spapr_hypercall (cpu=0x11540df0,
>> opcode=0xf000, args=0x7ffff4cf0030) at
>> /home/aik/p/qemu/hw/ppc/spapr_hcall.c:2014
>> #26 0x000000001033bff0 in kvm_arch_handle_exit (cs=0x11540df0,
>> run=0x7ffff4cf0000) at /home/aik/p/qemu/target/ppc/kvm.c:1684
>> #27 0x00000000100cc7c8 in kvm_cpu_exec (cpu=0x11540df0) at
>> /home/aik/p/qemu/accel/kvm/kvm-all.c:2391
>> #28 0x000000001008edf8 in qemu_kvm_cpu_thread_fn (arg=0x11540df0) at
>> /home/aik/p/qemu/cpus.c:1318
>> #29 0x000000001092c704 in qemu_thread_start (args=0x11588d90) at
>> /home/aik/p/qemu/util/qemu-thread-posix.c:519
>> #30 0x00007ffff7b58070 in start_thread (arg=0x7ffff550ebf0) at
>> pthread_create.c:335
>> #31 0x00007ffff7aa3a70 in clone () at
>> ../sysdeps/unix/sysv/linux/powerpc/powerpc64/clone.S:96
>> (gdb)
>>
> 

-- 
Alexey