[RFC v3 0/1] memory: Delete assertion in memory_region_unregister_iommu_notifier

[Eugenio Pérez]

I am able to hit this assertion when a Red Hat 7 guest virtio_net device
raises an "Invalidation" of all the TLB entries. This happens in the
guest's startup if 'intel_iommu=on' argument is passed to the guest
kernel and right IOMMU/ATS devices are declared in qemu's command line.

Command line:
/home/qemu/x86_64-softmmu/qemu-system-x86_64 -name \
guest=rhel7-test,debug-threads=on -machine \
pc-q35-5.1,accel=kvm,usb=off,dump-guest-core=off,kernel_irqchip=split \
-cpu \
Broadwell,vme=on,ss=on,vmx=on,f16c=on,rdrand=on,hypervisor=on,arat=on,tsc-adjust=on,umip=on,arch-capabilities=on,xsaveopt=on,pdpe1gb=on,abm=on,skip-l1dfl-vmentry=on,rtm=on,hle=on
 \
-m 8096 -realtime mlock=off -smp 2,sockets=2,cores=1,threads=1 -uuid \
d022ecbf-679e-4755-87ce-eb87fc5bbc5d -display none -no-user-config \
-nodefaults -rtc base=utc,driftfix=slew -global \
kvm-pit.lost_tick_policy=delay -no-hpet -no-shutdown -global \
ICH9-LPC.disable_s3=1 -global ICH9-LPC.disable_s4=1 -boot strict=on \
-device intel-iommu,intremap=on,device-iotlb=on -device \
pcie-root-port,port=0x8,chassis=1,id=pci.1,bus=pcie.0,multifunction=on,addr=0x1 
\
-device \
pcie-root-port,port=0x9,chassis=2,id=pci.2,bus=pcie.0,addr=0x1.0x1 \
-device \
pcie-root-port,port=0xa,chassis=3,id=pci.3,bus=pcie.0,addr=0x1.0x2 \
-device \
pcie-root-port,port=0xb,chassis=4,id=pci.4,bus=pcie.0,addr=0x1.0x3 \
-device \
pcie-root-port,port=0xc,chassis=5,id=pci.5,bus=pcie.0,addr=0x1.0x4 \
-device \
pcie-root-port,port=0xd,chassis=6,id=pci.6,bus=pcie.0,addr=0x1.0x5 \
-device \
pcie-root-port,port=0xe,chassis=7,id=pci.7,bus=pcie.0,addr=0x1.0x6 \
-device qemu-xhci,p2=15,p3=15,id=usb,bus=pci.2,addr=0x0 -device \
virtio-serial-pci,id=virtio-serial0,bus=pci.3,addr=0x0 -drive \
file=/home/virtio-test2.qcow2,format=qcow2,if=none,id=drive-virtio-disk0 \
-device \
virtio-blk-pci,scsi=off,bus=pci.4,addr=0x0,drive=drive-virtio-disk0,id=virtio-disk0,bootindex=1
 \
-netdev tap,id=hostnet0,vhost=on,vhostforce=on -device \
virtio-net-pci,netdev=hostnet0,id=net0,mac=52:54:00:0d:1d:f2,bus=pci.1,addr=0x0,iommu_platform=on,ats=on
 \
-device virtio-balloon-pci,id=balloon0,bus=pci.5,addr=0x0 -object \
rng-random,id=objrng0,filename=/dev/urandom -device \
virtio-rng-pci,rng=objrng0,id=rng0,bus=pci.6,addr=0x0 -s -msg \
timestamp=on

Full backtrace:

    at /home/qemu/hw/i386/intel_iommu.c:2468
    (mr=0x555557609330, addr=136, value=0x7ffde5dfe478, size=4, shift=0, 
mask=4294967295, attrs=...) at /home/qemu/memory.c:483
    (addr=136, value=0x7ffde5dfe478, size=4, access_size_min=4, 
access_size_max=8, access_fn=
    0x555555883d38 <memory_region_write_accessor>, mr=0x555557609330, 
attrs=...) at /home/qemu/memory.c:544
    at /home/qemu/memory.c:1476
    (fv=0x7ffde00935d0, addr=4275634312, attrs=..., ptr=0x7ffff7ff0028, len=4, 
addr1=136, l=4, mr=0x555557609330) at /home/qemu/exec.c:3146
    at /home/qemu/exec.c:3186
    (as=0x5555567ca640 <address_space_memory>, addr=4275634312, attrs=..., 
buf=0x7ffff7ff0028, len=4) at /home/qemu/exec.c:3277
    (as=0x5555567ca640 <address_space_memory>, addr=4275634312, attrs=..., 
buf=0x7ffff7ff0028, len=4, is_write=true)
    at /home/qemu/exec.c:3287

--

Tested with vhost-net, with a linux bridge to forward packets.
Forwarding with vhostuser interfaces + dpdk-testpmd io forwarding mode seems
broken also in v5.1.0-rc3.

v3: Skip the assertion in case notifier is a IOTLB one, since they can manage
    arbitrary ranges. Using a flag in the notifier for now, as Peter suggested.

v2: Actually delete assertion instead of just commenting out using C99

Eugenio Pérez (1):
  memory: Skip bad range assertion if notifier supports arbitrary masks

 hw/virtio/vhost.c     |  2 +-
 include/exec/memory.h |  2 ++
 softmmu/memory.c      | 10 ++++++++--
 3 files changed, 11 insertions(+), 3 deletions(-)

-- 
2.18.1