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Re: [Qemu-ppc] [Qemu-devel][PATCH 2/2] spapr: Add support for -vga optio

From: Benjamin Herrenschmidt
Subject: Re: [Qemu-ppc] [Qemu-devel][PATCH 2/2] spapr: Add support for -vga option
Date: Thu, 28 Jun 2012 07:39:34 +1000

On Wed, 2012-06-27 at 14:08 +0200, Alexander Graf wrote:
> Ben, mind to push a working SLOF, we we can just enable all of it in
> one go and don't have to commit #if 0'ed code?
> Rest looks reasonable to me.

Sure, SLOF was gated by the memop patch but we can push it now. However
I'd rather leave that #if 0 for now for cirrus...

There are several issues with cirrus at the moment. Off the top of my

 - The Xorg driver has bugs with physical addresses > 32-bit (even when
compiled 64-bit). I had a patch floating around, I need to refresh it
and get it merged.

 - There is another issue with the way it accesses legacy VGA space
which should be routed by the kernel to a bit of shmem but isn't, we
need to add support for a VGA hole to qemu (if we didn't already, I
don't remember now, I'll check that later).

 - cirrusfb in the kernel will explode due to various bugs in it
(basically assumes that on powerpc it's a prep machine and does horrible
things with resources). Even with that fixed we still have a problem
with color expansion

 - color expansion works by constantly replacing the memory region in
qemu that covers the frame buffer, flipping it between a direct mapping
of the fb vs. emulated registers. This triggers races & problems in our
kvm implementation. We need to fix them but we haven't yet.

So overall, let's keep cirrus off in that code path. It's still possible
to manually enable it with -device for development/debugging purposes.


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