[Qemu-devel] [Bug 1728256] Re: (Regression) Memory corruption in Windows 10 guest / amd64

[Wüstengecko]

Unfortunately I have bad news, but I also have (kind of) good news.
Bad news is, 2.9 is NOT stable, contrary to what I believed earlier.
Good news is, I found a correlation between the crashes and converting large 
video files on an SMB share with ffmpeg, so effectively copying slowly with 
simultaneously high CPU load. In that constellation it crashed a few times 
after just hours (instead of days sometimes). I suspect it might be a network 
related issue. I am now testing the different virtual network hardware that 
qemu supports (which proved to be difficult due to lack of driver support in 
Windows).

On that note, I remember right after setting up the VM I had some
strange networking related hangup issues with the rtl8139 virtual
adapter - the default -, where the VM would slowly grind to a complete
halt over a few seconds when I started a very network-heavy task (like
copying something from the host via SMB into the VM). I could prevent
the hang when I paused the copying for a few seconds. At that time I
assumed it was the hardware registering as 100Mbps adapter, but the
actual load being about 4 times that on average (during copying of
course), with peaks significantly higher (about 15-20 times). That issue
completely went away after switching the virtual network hardware to
virtio (which registers as 10Gbps adapter), and I considered that case
closed.

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https://bugs.launchpad.net/bugs/1728256

Title:
  (Regression) Memory corruption in Windows 10 guest / amd64

Status in QEMU:
  New

Bug description:
  I have a Win 10 Pro x64 guest inside a qemu/kvm running on an Arch x86_64 
host. The VM has a physical GPU passed through, as well as the physical USB 
controllers, as well as a dedicated SSD attached via SATA; you can find the 
complete libvirt xml here: https://pastebin.com/U1ZAXBNg
  I built qemu from source using the qemu-minimal-git AUR package; you can find 
the build script here: 
https://aur.archlinux.org/cgit/aur.git/tree/PKGBUILD?h=qemu-minimal-git (if you 
aren't familiar with Arch, this is essentially a bash script where build() and 
package() are run to build the files, and then install them into the $pkgdir to 
later tar them up.)

  Starting with qemu v2.10.0, Windows crashes randomly with a bluescreen
  about CRITICAL_STRUCTURE_CORRUPTION. I also tested the git heads
  f90ea7ba7c, 861cd431c9 and e822e81e35, before I went back to v2.9.0,
  which is running stable for over 50 hours right now.

  During my tests I found that locking the memory pages alleviates the
  problem somewhat, but never completely avoids it. However, with the
  crashes occuring randomly, that could as well be false conclusions; I
  had crashes within minutes after boot with that too.

  I will now start `git bisect`ing; if you have any other suggestions on
  what I could try or possible patches feel free to leave them with me.

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