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Date: Wed, 12 May 2010 09:39:50 +0300
From: Avi Kivity <avi@redhat.com>
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Subject: Re: [Qemu-devel] Re: QEMU-KVM and video performance
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To: Gerhard Wiesinger <lists@wiesinger.com>
Cc: qemu-devel@nongnu.org, kvm@vger.kernel.org

On 05/12/2010 09:14 AM, Gerhard Wiesinger wrote:
> On Mon, 10 May 2010, Avi Kivity wrote:
>
>> On 05/09/2010 10:35 PM, Gerhard Wiesinger wrote:
>>>>>
>>
>> For 256 color more the first priority is to find out why direct 
>> mapping is not used.  I'd suggest tracing the code that makes this 
>> decision (in hw/*vga.c) and seeing if it's right or not.
>
> I think this is because A000 is not initialized for KVM (see log below 
> and logging patch attached).

Why isn't it initialized?

Did the guest configure things such as it is impossible to map it 
directly?  Or does the configuration allow direct mapping and qemu 
incorrectly decides that it cannot direct map?

Best would be to print out all the configuration registers and interpret 
them according to the specification.


>
> vga_dirty_log_start
> vga_dirty_log_start_mapping_lfb_vram_mapped, start=0x000A0000, 
> len=0x00008000
> BUG: kvm_dirty_pages_log_change: invalid parameters 
> 00000000000a0000-00000000000a7fff

Why does this happen?

-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.