user_to_phys() without mmap?

I'm trying to use a framebuffer from user space (think plain video ram, not some PCI or AGP video card), but mmap'ing from kernel space into user space is causing large latencies and unsightly artifacts. It appears that anything written into the mmap'ed user memory is in fact being copied into kernel space.

What I was actually hoping was that the memory manager would simply map the underlying physical pages directly into the user's address space. I think that's simple enough to do in theory, but there is much that I don't know about Linux kernel internals, so in practice who knows?

Has anybody else made physical memory directly accessible from user space, without resorting to copying data back and forth continually?
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Relevant Pages

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