Hi Bambang, thanks a lot for your testing! I'll need you to test one
more kernel to be 100% sure of the issue and be able to fix it. Let me
elaborate on what's happening.
So, since kernel 4.15.0-136 we included a very complex KVM fix for a
kind of "race" in interrupt window triggered by David Woodhouse [0] and
analyzed by some members of KVM community (causing a live-lock - I
suggest reading [0], very informative thread). The fix was proposed in
the form of a patch series containing 2 patches [1] from Paolo Bonzini.
This was merged in Ubuntu though the stable tree, in the form of the
following commit:
71cc849b7093 ("KVM: x86: Fix split-irqchip vs interrupt injection window
request") [2]
The problem is that such commit has a companion required commit, which
was not proposed in the stable tree. In fact, there was a confusion
among KVM community and the stable maintainer [3], due to the lack of
such missing commit - because of that, the series was removed from
stable trees 4.14.y and 4.9.y, but the solo commit was merged alone in
Ubuntu kernel 4.15.
My theory is that this commit alone is causing an odd behavior
(specially since dosemu2 seems to make use of leagacy PIC instead of
APIC), so the fix would be to merge the companion commit in Ubuntu tree:
72c3bcdcda49 ("KVM: x86: handle !lapic_in_kernel case in
kvm_cpu_*_extint") [4]
It's interesting to note that after the stable confusion in [3], both
commits were removed from 4.9.y and 4.14.y trees - I intend to submit
both to 4.14.y tree after the next test, as well as merge it on Ubuntu
kernel.
I'll defer the test for next comment, in order to not pollute this one (which
is already big and a bit over-detailed).
Cheers,
Guilherme
[0]
https://lore.kernel.org/kvm/62918f65ec78f8990278a6a0db0567968fa23e49.ca...@infradead.org/
[1] https://lore.kernel.org/kvm/20201127112114.3219360-1-pbonz...@redhat.com/
[2] http://git.kernel.org/linus/71cc849b70
[3]
https://lore.kernel.org/stable/d29c4b25-33f6-8d99-7a45-8f4e06f5a...@redhat.com/
[4] http://git.kernel.org/linus/72c3bcdcda
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https://bugs.launchpad.net/bugs/1917138
Title:
kernel 4.15.0-136 causes dosemu2 with kvm freezes
Status in Dosemu2:
New
Status in linux package in Ubuntu:
In Progress
Bug description:
With the latest kernel 4.15.0-136 updates on ubuntu 18.04 and ubuntu
16.04, dosemu2 with kvm freezes boot.
dosemu2 source: https://github.com/dosemu2/dosemu2
dosemu2 package can be obtained from
https://launchpad.net/~dosemu2/+archive/ubuntu/ppa
1. ubuntu version
lsb_release -rd
Description: Ubuntu 18.04.5 LTS
Release: 18.04
2. package version
$ apt-cache policy dosemu2
dosemu2:
Installed: (none)
Candidate: (none)
Version table:
2.0~pre8-2 -1
100 /var/lib/dpkg/status
3. What is expected to happen: The dosemu program runs fine as in previous
kernel version
4. What happened instead: The dosemu freezes on loading
I have also reported this problem to dosemu2 developer, here is my bug report:
https://github.com/dosemu2/dosemu2/issues/1404
To manage notifications about this bug go to:
https://bugs.launchpad.net/dosemu2/+bug/1917138/+subscriptions
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