What does this mean?

[Riemann]

Just had a meeting with my manager about year end performance review. He said he wanted to give me a heads up that they've received some negative feedback about me, and they (boss + bosses boss) were going to meet with HR next week to discuss. I kept pressing him for more information, but due to privacy and all that junk, he couldn't elaborate. I asked him if my job is safe, and he said he thought so.

My thoughts are that if they're getting HR involved, it can't be something as trivial as wow, he really screwed up this project. Or he didn't do a good job at whatever. I'm thinking I must have said something to offend someone and this is the course of action that they must take. I conclude this because I've done all that's asked of me as far as work goes.

Thoughts? Should I be worried about being fired? Do you think my thought process is accurate?

Thanks.