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

[Akio Takebe <takebe_akio@xxxxxxxxxxxxxx>]

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

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