From mboxrd@z Thu Jan  1 00:00:00 1970
From: Akio Takebe <takebe_akio@jp.fujitsu.com>
Subject: Re: guest attempted write to read-only memory page.
Date: Thu, 25 Dec 2008 10:54:06 +0900
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To: "Tian, Kevin" <kevin.tian@intel.com>
Cc: "xen-devel@lists.xensource.com" <xen-devel@lists.xensource.com>, 'Keir Fraser' <keir.fraser@eu.citrix.com>
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Tian, Kevin wrote:
>> From: Tian, Kevin
>> Sent: Monday, December 22, 2008 9:11 PM
>>> Possibly we should silence the shadow code too, at least 
>>> perhaps while in
>>> real mode or for a certain EIP range.
>>>
>> I'm not sure that's the right fix. Why is write access to rom disabled
>> before rom scan when etherboot is known to have write requirement?
>>
>> #ifdef HVMASSIST
>>  call _enable_rom_write_access
>>  call _clobber_entry_point
>>  call _copy_e820_table
>>  call smbios_init
>>  call _disable_rom_write_access
>> #endif
>>
>>  call _init_boot_vectors
>>
>>  mov  cx, #0xc800  ;; init option roms
>>  mov  ax, #0xe000
>>  call rom_scan
>>
>> 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.

Sorry for my late response.
That's a bug of mine.

Some option ROMs would do write accesses.
So rombios need to enable write acess before rom_scan.
I'll post a patch to fix.

Best Regards,

Akio Takebe