On Wed, Nov 13, 2019 at 03:44:28PM +1100, Alexey Kardashevskiy wrote: > > > On 12/11/2019 18:08, Michael S. Tsirkin wrote: > > On Tue, Nov 12, 2019 at 02:53:49PM +1100, 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. > > > > In fact clearing bus master should disable ring access even > > without the IOMMU. > > Once you do this you should not wait for rings to be processed, > > it is safe to assume they won't be touched again and just > > free up any buffers that have not been used. > > > > Why don't you see this without IOMMU? > > Because without IOMMU, virtio can always access rings, it does not need > bus master address space for that.
Right and that's a bug in virtio scsi. E.g. virtio net checks bus mastering before each access. Which is all well and good, but we can't just break the world so I guess we first need to fix SLOF, and then add a compat property. And maybe keep it broken for legacy ... > > > It's a bug I think, probably there to work around buggy guests. > > > > So pls fix this in SLOF and then hopefully we can drop the > > work arounds and have clearing bus master actually block DMA. > > > Laszlo suggested writing 0 to the status but this does not seem helping, > with both ioeventfd=true/false. It looks like setting/clearing busmaster > bit confused memory region caches in QEMU's virtio. I am confused which > direction to keep digging to, any suggestions? Thanks, > to clarify you reset after setting bus master? right? > > > > >> Hacking SLOF to not clear BUSMASTER makes virtio-scsi work but it is > >> hardly a right fix. > >> > >> Is this something expected? Thanks, > >> > >> > >> 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 > > > > -- > Alexey
