I receive a warning that a particular core is deprecated or obsoleted. What does that mean? If I don't want to upgrade my core, how can I preserve a particular core?
There are three states any piece of IP can take: Active, Deprecated, and Obsolete. Only Active and Deprecated cores are supported by the hotline. When a new version of a core comes out, the latest version is marked as Active, and older versions are marked as Deprecated. At a certain point, a version of IP will be removed from the build. In the software release before this happens, a core will be marked as Obsolete. At that point, the design will not build with Obsolete IP.
If I don't want to upgrade my core, how can I preserve a particular obsoleted core?
If you are content with a particular core, and it is being marked Obsolete (check the PlatGen log file to find out if you have any Obsolete cores in your design), you can copy the core design files from the EDK IP repository (%EDK%\hw\XilinxProcessorIPLib\pcores) to your local pcore directory (<my project directory>\pcore\).
Modify the MPD file in the local pcore directory so that it is no longer set to Obsolete. Set it to either Deprecated or Active. This will preserve your core for future builds of your project, despite the core being Obsoleted.