[Qemu-devel] [Bug 1719339] [NEW] serial8250: too much work for irq3

[Denys Zagorui]

Public bug reported:

It's know issue and sometimes mentioned since 2007. But it seems not
fixed.

http://lists.gnu.org/archive/html/qemu-devel/2008-02/msg00140.html
https://bugzilla.redhat.com/show_bug.cgi?id=986761
http://old-list-archives.xenproject.org/archives/html/xen-devel/2009-02/msg00696.html

I don't think fixes like increases PASS_LIMIT
(/drivers/tty/serial/8250.c) or remove this annoying message
(https://patchwork.kernel.org/patch/3920801/) is real fix. Some fix was
proposed by H. Peter Anvin  https://lkml.org/lkml/2008/2/7/485.

Can reproduce on Debian Strech host (Qemu 1:2.8+dfsg-6+deb9u2), Ubuntu
16.04.2 LTS (Qemu 1:2.5+dfsg-5ubuntu10.15) also tried to use master
branch (QEMU emulator version 2.10.50 (v2.10.0-766-ga43415ebfd-dirty))
if we write a lot of message into console (dmesg or dd if=/dev/zero
of=/dev/ttyS1).

/usr/local/bin/qemu-system-x86_64 -name guest=ultra1,debug-threads=on -S
-object
secret,id=masterKey0,format=raw,file=/var/lib/libvirt/qemu/domain-27-ultra1
/master-key.aes -machine pc-i440fx-2.8,accel=kvm,usb=off,dump-guest-
core=off -cpu Skylake-
Client,ds=on,acpi=on,ss=on,ht=on,tm=on,pbe=on,dtes64=on,monitor=on,ds_cpl=on,vmx=on,smx=on,est=on,tm2=on,xtpr=on,pdcm=on,osxsave=on,tsc_adjust=on,clflushopt=on,pdpe1gb=on
-m 4096 -realtime mlock=off -smp 4,sockets=1,cores=4,threads=1 -uuid
4537ca29-73b2-40c3-9b43-666de182ba5f -display none -no-user-config
-nodefaults -chardev
socket,id=charmonitor,path=/var/lib/libvirt/qemu/domain-27-ultra1/monitor.sock,server,nowait
-mon chardev=charmonitor,id=monitor,mode=control -rtc
base=utc,driftfix=slew -global kvm-pit.lost_tick_policy=delay -no-hpet
-no-shutdown -global PIIX4_PM.disable_s3=1 -global PIIX4_PM.disable_s4=1
-boot strict=on -device ich9-usb-ehci1,id=usb,bus=pci.0,addr=0x8.0x7
-drive file=/home/dzagorui/csr/csr_disk.qcow2,format=qcow2,if=none,id
=drive-ide0-0-0 -device ide-hd,bus=ide.0,unit=0,drive=drive-
ide0-0-0,id=ide0-0-0,bootindex=1 -netdev tap,fd=26,id=hostnet0 -device
e1000,netdev=hostnet0,id=net0,mac=52:54:00:a9:4c:86,bus=pci.0,addr=0x3
-chardev
socket,id=charserial0,host=127.0.0.1,port=4000,telnet,server,nowait
-device isa-serial,chardev=charserial0,id=serial0 -chardev
socket,id=charserial1,host=127.0.0.1,port=4001,telnet,server,nowait
-device isa-serial,chardev=charserial1,id=serial1 -device virtio-
balloon-pci,id=balloon0,bus=pci.0,addr=0x2 -msg timestamp=on

** Affects: qemu
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/1719339

Title:
  serial8250: too much work for irq3

Status in QEMU:
  New

Bug description:
  It's know issue and sometimes mentioned since 2007. But it seems not
  fixed.

  http://lists.gnu.org/archive/html/qemu-devel/2008-02/msg00140.html
  https://bugzilla.redhat.com/show_bug.cgi?id=986761
  
http://old-list-archives.xenproject.org/archives/html/xen-devel/2009-02/msg00696.html

  I don't think fixes like increases PASS_LIMIT
  (/drivers/tty/serial/8250.c) or remove this annoying message
  (https://patchwork.kernel.org/patch/3920801/) is real fix. Some fix
  was proposed by H. Peter Anvin  https://lkml.org/lkml/2008/2/7/485.

  Can reproduce on Debian Strech host (Qemu 1:2.8+dfsg-6+deb9u2), Ubuntu
  16.04.2 LTS (Qemu 1:2.5+dfsg-5ubuntu10.15) also tried to use master
  branch (QEMU emulator version 2.10.50 (v2.10.0-766-ga43415ebfd-dirty))
  if we write a lot of message into console (dmesg or dd if=/dev/zero
  of=/dev/ttyS1).

  /usr/local/bin/qemu-system-x86_64 -name guest=ultra1,debug-threads=on
  -S -object
  secret,id=masterKey0,format=raw,file=/var/lib/libvirt/qemu/domain-27-ultra1
  /master-key.aes -machine pc-i440fx-2.8,accel=kvm,usb=off,dump-guest-
  core=off -cpu Skylake-
  
Client,ds=on,acpi=on,ss=on,ht=on,tm=on,pbe=on,dtes64=on,monitor=on,ds_cpl=on,vmx=on,smx=on,est=on,tm2=on,xtpr=on,pdcm=on,osxsave=on,tsc_adjust=on,clflushopt=on,pdpe1gb=on
  -m 4096 -realtime mlock=off -smp 4,sockets=1,cores=4,threads=1 -uuid
  4537ca29-73b2-40c3-9b43-666de182ba5f -display none -no-user-config
  -nodefaults -chardev
  
socket,id=charmonitor,path=/var/lib/libvirt/qemu/domain-27-ultra1/monitor.sock,server,nowait
  -mon chardev=charmonitor,id=monitor,mode=control -rtc
  base=utc,driftfix=slew -global kvm-pit.lost_tick_policy=delay -no-hpet
  -no-shutdown -global PIIX4_PM.disable_s3=1 -global
  PIIX4_PM.disable_s4=1 -boot strict=on -device ich9-usb-
  ehci1,id=usb,bus=pci.0,addr=0x8.0x7 -drive
  file=/home/dzagorui/csr/csr_disk.qcow2,format=qcow2,if=none,id=drive-
  ide0-0-0 -device ide-hd,bus=ide.0,unit=0,drive=drive-
  ide0-0-0,id=ide0-0-0,bootindex=1 -netdev tap,fd=26,id=hostnet0 -device
  e1000,netdev=hostnet0,id=net0,mac=52:54:00:a9:4c:86,bus=pci.0,addr=0x3
  -chardev
  socket,id=charserial0,host=127.0.0.1,port=4000,telnet,server,nowait
  -device isa-serial,chardev=charserial0,id=serial0 -chardev
  socket,id=charserial1,host=127.0.0.1,port=4001,telnet,server,nowait
  -device isa-serial,chardev=charserial1,id=serial1 -device virtio-
  balloon-pci,id=balloon0,bus=pci.0,addr=0x2 -msg timestamp=on

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