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

From: Alexander Graf
Subject: Re: [Qemu-ppc] [Qemu-devel][PATCH 2/2] spapr: Add support for -vga option
Date: Wed, 27 Jun 2012 23:42:10 +0200

On 27.06.2012, at 23:39, Benjamin Herrenschmidt wrote:

> 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
> head:
> - 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.

It shouldn't be an #if 0 but an if (cirrus) hw_abort() then though. Otherwise 
we'd just silently ignore the option.


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