alexxnica/xen

Branches

• xen-44 is the branch for Xen 4.4
• xen-46 is the branch for Xen 4.6 (currently supported)
• xen-48 is the branch for Xen 4.8

repo script

The main directory has a script called repo with a number of 'utility' functions. A quick summary can be found by running ./repo help.

None of these functions call sudo; the content can be found in lib/*.sh, and configuration for current version, &c can be found in sources.cfg.

Building

The first thing to do, after checking out the appropriate branch, is to get the required source files. Do this by running the included script:

./repo get-sources

Then do an rpmbuild (obviously replacing el7 with el6 for CentOS 6):

rpmbuild --define "_topdir $PWD" --define "dist .el7" -bb SPECS/*.spec

Or, make an srpm and submit it to koji:

rpmbuild --define "_topdir $PWD" --define "dist .el7" -bs SPECS/*.spec

cbs build virt7-xen-46-el7 SRPMS/*.el7.src.rpm

Adding qemu patches

Add qemu patches the normal way: by copying the patches to SOURCES, adding a PatchNN: line to the xen.spec file, and then adding %patchNN -p1 in the appropriate place in the file file.

For the 'NN', we use the following number sequence for patches:

• 1000+: blktap
• 2000+: qemu-xen
• 3000+: qemu-xen-traditional

Take XSA-130 for example; this had two patches, xsa130-qemuu.patch, and xsa130-qemut.patch, for qemu-xen ("qemu upstream") and qemu-traditional, respectively. To add those patches do the following:

Copy them into SOURCES, and then add them to git:

cp  /path/to/xsas/xsa130-qemu*.patch SOURCES/

Then add the following two lines in the "Patch" section:

Patch2001: xsa130-qemuu.patch

Patch3001: xsa130-qemut.patch

And finally, add the the following line after pushd tools/qemu-xen:

%patch2001 -p1

And the following line after pushd tools/qemu-xen-traditional:

%patch3001 -p1

Working with the Xen patchqueue

The core Xen patchqueue is stored as a git "am" file. This makes it a tiny bit more difficult to add a single patch, but makes it much easier to work with when it comes to rebasing to a new version of Xen.

Most of these operations are implemented in the repo script; a breakdown of what's going on inside is included to help understanding. To work with the script requires that you have both git and stackgit (stg) installed.

Making a git tree with the patchqueue

Start by cloning the upstream git repository:

./repo make-tree

This will create a tree in UPSTREAM/xen.git based on the XEN_VERSION set in sources.cfg. Suppose that XEN_VERSION is set to 4.6.0. make-tree will make the following branches:

• base/4.6.0: A branch based on RELEASE-4.6.0

• centos/pq/4.6.0: A branch based on the above, but with the CentOS "patchqueue" (SOURCES/xen-queue.am) applied.

To do this manually:

mkdir UPSTREAM
cd UPSTREAM
git clone git://xenbits.xenproject.org/xen.git xen.git
cd xen.git

Check out the appropriate release tag:

git checkout -b 4.6.0 RELEASE-4.6.0

Now create a stackgit branch for the patches:

stg branch --create centos/pq/4.6.0

And import the patchqueue:

stg import -M ${path_to_package_repo}/SOURCES/xen-queue.am

Importing patches to the patchqueue

Once you have the tree, you can import new patches to the queue like this:

./repo import-patches /path/to/xsas/xsa150.patch

Once you've imported all the patches and everything works, update SOURCES/xen-queue.am like this:

./repo sync-queue

Or to do the above manually, from the UPSTREAM/xen.git repo:

stg import -m /path/to/xsas/xsa150.patch

When you're done, export the patchqueue back to xen-queue.am:

git format-patch --stdout -N RELEASE-4.6.0 > ${path_to_package_repo}/SOURCES/xen-queue.am

And finally, run the script provided in this repo to remove extraneous information from the patchqueue (such as the version of git you're running) and reduce the diff size:

./pqnorm.pl

Rebasing to a new version of Xen

Suppose you 4.6.1 comes out, and you want to rebase the patchqueue. Assuming you took my advice above, you already have the patchqueue in stg format from above.

You can start the process as follows:

./repo rebase new=4.6.1

This will create base/4.6.1 and centos/pq/4.6.1, and begin rebasing the existing patchqueue. This rarely succeeds completely the first time; you'll have to manually fix up the process (often by removing old XSAs). After fixing things up, finish the process by running

./repo rebase-post

This will sync the patchqueue, as well as updating XEN_VERSION in sources.cfg. You'll have to update xen.spec (see below) and call get-sources to fetch the new tarball.

To do it manually, first clone the entire patchqueue (so you have a backup in case things go wrong):

git checkout centos/pq/4.6.0
stg branch --clone centos/pq/4.6.1

Then rebase to the new version, checking for merged patches:

stg rebase -m RELEASE-4.6.1

Many of the patches may fail to apply, in which case you'll need to do through the process of fixing them up and doing stg refresh, then repeating with stg push -a until they all apply.

Patches which already exist in upstream (for instance, XSAs) will automatically be turned into empty patches; you can have stackgit get rid of these like this:

stg clean

Now export the patchqueue:

git format-patch --stdout -N RELEASE-4.6.1 > ${path_to_package_repo}/SOURCES/xen-queue.am

Clean it up:

./pqnorm.pl

Update get_sources.sh with the new version:

XEN_VERSION=4.6.1

And run it again to fetch the new version (and make sure it still works properly):

./repo get-sources

Update SPECS/xen.spec with the new version and changelog, and build.

You may need to remove qemu-related patches from xen.spec as well (See "Adding qemu patches" for more information.)

Updating your xen.git tree based on updates to this repo

Suppose someone else pushes some changes to CentOS-virt7/xen that modifies the patchqueue. To update your tree:

./repo sync-tree

Or do it manually:

git checkout base/4.6.1
stg branch --delete --force centos/pq/4.6.1
stg branch --create centos/pq/4.6.1
stg import -M ../../SOURCES/xen-queue.am