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RE: [Xen-devel] guest attempted write to read-only memory page.

To: 'Keir Fraser' <keir.fraser@xxxxxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: RE: [Xen-devel] guest attempted write to read-only memory page.
From: "Tian, Kevin" <kevin.tian@xxxxxxxxx>
Date: Mon, 22 Dec 2008 22:21:04 +0800
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Cc: 'Akio Takebe' <takebe_akio@xxxxxxxxxxxxxx>
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Thread-topic: [Xen-devel] guest attempted write to read-only memory page.
>From: Keir Fraser [mailto:keir.fraser@xxxxxxxxxxxxx] 
>Sent: Monday, December 22, 2008 9:43 PM
>
>On 22/12/2008 13:20, "Tian, Kevin" <kevin.tian@xxxxxxxxx> wrote:
>
>>> Should we move disable action to post rom_scan? If shadow warning
>>> is simply silenced for such case, it seems breaking the purpose of
>>> disable_dom_write_access...
>>> 
>> 
>> I make a quick test, that warning disappears after moving disable
>> action post rom_scan. But I haven't found the place triggering such
>> write violation, as in previous revision write access is 
>also disabled
>> before rom_scan. It could come from recent bochs update on
>> expansion rom part by 18931.
>
>Yes, I can repro the warnings. They are due to the vm86 acceleration
>changes. 
>

I saw you removed the warning in latest tree, but sorry that I'm still
a bit confused about logic here. Could you help clarify the underlying
story to me? :-) Why is such write attempt legitimate? Is the emulation
a dummy nop or actually emulated? 

Thanks,
Kevin
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