PCI Configuration Space

[Joy]

Hi,

Please, forgive me about this silly question, but for this beginning 
learner, if somebody helps me, it would be appreciated.

I've googled before, of course, but it's not easy to figure out.

The question is simple.

If I am able to read PCI device's configuration space, where is it?

Is it in Main Memory (in general, DDR3) mapped? Or Is it in the device's 
own memory?

Joy