Monthly Archives: May 2013

Fedora 19 Virtualization Test Day — 28MAY2013

Heya,

Rich Jones already mentioned it a couple of days ago. This is just another gentle reminder.

The test day wiki page has all the information. Also, Kamil Paral has kindly put together (thanks!) a test day specific Fedora 19 image .

Goes without saying, you can always update the results before/after the test day.

IRC – #fedora-test-day

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Nested Virtualization — KVM, Intel, with VMCS Shadowing

[Previous installments on Nested Virtualization with KVM and Intel.]

This is part of some recent testing that I’ve been doing with upstream KVM (for 3.10.1). The threads linked here has initial tests bench-marking kernel compile (with make defconfig, a default config file) times in L2. And some minimal guestfish appliance start-up timings in L1.

Some details:

  • Setup information to test with VMCS (Virtual Machine Control Structure) Shadowing. In brief, VMCS Shadowing — a processor specific feature — as described upstream, can reduce the overhead of nested virtualization by reducing the number of VMExits from L1 to L0.
  • Simple scripts used to create L1 and L2.
  • Libvirt XMLs of L1, L2 guests, for reference.

The gritty details of reasons for VMExits are described in Intel architecture manuals, Volume 3b, APPENDIX 1.

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Fetching Rawhide Kernel builds using koji

To fetch rawhide kernels from Koji (Fedora build system), this is what I do:

Install the group “RPM Development Tools” to get koji packages

$ yum groupinstall "RPM Development Tools" 

NOTE: If you’re using versions < Fedora 19, please do: yum groupinstall "Development Tools"

Find the latest kernel in Rawhide

$ koji latest-pkg rawhide kernel                                                                      
Build                                     Tag                   Built by
----------------------------------------  --------------------  ----------------
kernel-3.10.0-0.rc0.git26.1.fc20          f20                   jwboyer

Download the resultant kernel from the o/p of the above command.

$ koji download-build \
  --arch=x86_64 kernel-3.10.0-0.rc0.git23.1.fc20 

Finally, install it

$ yum localinstall *.rpm 

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Search for a specific patch from an upstream PULL request (KVM) in Fedora Rawhide Kernel

Before I use the latest rawhide kernel for a test, I had to ensure some specific patches made into it from KVM upstream GIT PULL request . This is how I tried:

Fetch the Rawhide Kernel SRPM

Install the rawhide SRPM:

 
# Move into SRPMS directory
$ cd ~/rpmbuild/SRPMS 

# Fetch the SRPM
$ wget http://kojipkgs.fedoraproject.org//packages/kernel/3.10.0/0.rc0.git23.1.fc20/src/kernel-3.10.0-0.rc0.git23.1.fc20.src.rpm 

# Install the kernel SRPM
$ rpm -ivh kernel-3.10.0-0.rc0.git23.1.fc20.src.rpm 

First, simpler way

git-describe to the rescue: Each Fedora rawhide kernel changelog has the precise output of Linus’ tree (thanks jwb!). So, let’s run it on the upstream kernel tree.

 
# Clone Linus' tree (or traverse to its path if it already exists)
# git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
$ cd linux 

# Run:
$ git describe
v3.9-11789-ge0fd9af

The above output can be understood as (from git-describe man page): The current head of the “parent” branch is based on v3.9, and is 11789 commits ahead of it; with a hash suffix ge0fd9af: where “-g” (stands for “git”), e0fd9af is the 7-character abbreviation for the tip commit (which was — e0fd9affeb64088eff407dfc98bbd3a5c17ea479)

Now, compare the above tag from the tag mentioned in changelog of Fedora Rawhide Kernel

$ rpm -q kernel --changelog | head -2 
* Thu May 09 2013 Josh Boyer  - 3.10.0-0.rc0.git23.1
- Linux v3.9-11789-ge0fd9af

Second, a more convoluted way to ensure a specific patch is in

Check upstream KVM tree, for the latest commit —
db6ae6158186a17165ef990bda2895ae7594b039

# Clone the upstream KVM git
$ git clone git://git.kernel.org/pub/scm/virt/kvm/kvm.git

# Traverse into its directory
$ cd kvm 

# Get the latest commit ID
$ git log tags/kvm-3.10-1 | head -1
db6ae6158186a17165ef990bda2895ae7594b039 

Now, get details the above commit. Its commit’s short description says: “kvm: Add compat_ioctl for device control API”

$  git log -p db6ae6158186a17165ef990bda2895ae7594b039 
.....
+       .compat_ioctl = kvm_device_ioctl, 

(that’s the first line of change)

Let’s grep for that string in our just installed kernel sources tree

$ cd ~/rpmbuild/SOURCES/ 

# Copy the patch file archive into a temp directory
$  cp patch-3.9-git23.xz /var/tmp/test/ 

# Extract & list it
$ unxz patch-3.9-git23.xz 
$ ls
patch-3.9-git23 

# grep for that specific line
$ grep ".compat_ioctl = kvm_device_ioctl" patch-3.9-git23 
+       .compat_ioctl = kvm_device_ioctl,

So, the above confirms that the patch (and the KVM GIT PULL request is contained in the koji rawhide build.

And the entire PULL request for KVM updates is merged with this commit ID – 01227a889ed56ae53aeebb9f93be9d54dd8b2de8.

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Very late post — KVM Forum 2012 (incoherent) notes

While talking to Amit (thanks!) on IRC, he asked if I ever managed to take notes from the talks I attended at KVM Forum 2012 (side note – that page is up2date with slides from most talks). I did scribble some incoherent notes, but forgot to blog about it. Here we go — http://kashyapc.fedorapeople.org/virt/kvm-forum-2012-notes.txt

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