[Xen-devel] Re: [PATCH][RFC] gfx_passthru: warning when vgabios rom has invalid checksum

[Weidong Han <weidong.han@xxxxxxxxx>]

Noboru Iwamatsu wrote:
> Hi,
>
>  >> Intel DX58SO + GeForce GTS250:        checksum is OK.
>  >> Intel DX58SO + GeForce 9600GT:        checksum is OK.
>  >> Fujitsu Q35 M/B + IGD:                checksum is bad.
>  >>
>  > What does "checksum is bad" mean here?
>
> It means shadowed VGABIOS has invalid checksum
> and requires recalculating.
>
>  >> What do you think, Weidong?
>  >> Is just warning enough? Or, should we stop loading the rom?
>  >>
>  >>
>  > Does it still work or not when checksum is bad? If it works, we should
>  > not stop loading the rom.
>
> When the checksum is bad,
> if it is not recalculated, guest has some trouble about handling the
> VGA (unable to show BIOS screen, unable to load the gfx driver
> properly, ...).
For this case, it's reasonable to warning and stop loading rom. We 
didn't encounter this issue.
> If it is recalculated, it seems to work fine.
>   
How did you recalculate it? is it possible to recalculate it when detect 
invalid checksum?
Regards,
Weidong

> Regards,
> Noboru.
>
>   
> > Noboru Iwamatsu wrote:
> >     
> > > Hi,
> > >
> > > According to the "PCI Firmware Spec Rev 3.0",
> > > the system firmware have to write the new checksum after resizing
> > > the expansion ROM area.
> > >
> > > So, when re-using the shadowed VGABIOS, the checksum must
> > > be valid, and if it is invalid, we should consider the BIOS has
> > > a bug or memory area is corrupted.
> > >
> > > This patch just add the warning message when checksum requires
> > > recalculation.
> > >
> > > I tried this following environments.
> > >
> > > Intel DX58SO + GeForce GTS250:  checksum is OK.
> > > Intel DX58SO + GeForce 9600GT:  checksum is OK.
> > > Fujitsu Q35 M/B + IGD:          checksum is bad.
> > >
> > >       
> > What does "checksum is bad" mean here?
> >     
> > > What do you think, Weidong?
> > > Is just warning enough? Or, should we stop loading the rom?
> > >
> > >
> > >       
> > Does it still work or not when checksum is bad? If it works, we should
> > not stop loading the rom.
> >
> > Regards,
> > Weidong
> >     
> > > Regards,
> > > Noboru.
> > >
> > >       
>
>   

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