On Tue, Nov 03, 2009 at 12:24:15AM +0100, Alexander Graf wrote:

quoted

Also, we still need to keep the local frame buffer copy in sync so we
can mmap and read from it, right? So it's not really worth it
probably...

But then again we could just try to be closer to a real graphics card.  
What if we'd set up a memory region on the host that is basically our  
graphics frame buffer? For S390 we could just append the graphics memory 
to the guest's memory.

We could use that as backing buffer in the qemu graphics frontend and as 
frame buffer in the Linux fbdev layer, similar to what real graphics 
cards set up.

Using shared memory pages between host and guest seems like a natural
way to implement paravirtualized graphics card. Most things are
straightforward, only a little problematic thing is when fbdev 
is mmaped from guest to userspace - you have to detect writes
and notify host that it changed.

-- 
Elen sila lumenn' omentielvo

Ondrej 'SanTiago' Zajicek (email: santiago@crfreenet.org)
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"To err is human -- to blame it on a computer is even more so."