Re: [Xen-devel] [PATCH] VT-d: improve RMRR validity checking

[Weidong Han <weidong.han@xxxxxxxxx>]

Keir Fraser wrote:
> If we want to keep iommu=1 as default, then it is unacceptable to fail to
> boot on a fairly wide range of modern systems. We have to warn-and-disable,
> partially or completely, unless iommu=force is specified. Or we need to
> revert to iommu=0 as the default.
>
> What do you think, Weidong?
>   
Yes. I agree to warn-and-disable for these BIOS issues, and consider 
security more when iommu=force. Therefore I will implement a patch based 
on Nororu's patch.
Regards,
Weidong

>  -- Keir
>
> On 21/01/2010 14:17, "Sander Eikelenboom" <linux@xxxxxxxxxxxxxx> wrote:
>
>   
> > Hello Weidong,
> >
> > The problem is most vendor's just don't fix it and ignore the problem
> > completely.
> > Most often hiding them selves behind: come back when it's a problem with
> > Microsoft Windows, that the only single thing we support (and no other
> > software, so no vmware, no xen, no linux, perhaps even no hypervisor)
> > Well I don't know if the virtual pc in windows 7 supports an iommu now, but it
> > didn't in the past as far as i know, so any complain bounces off, and there it
> > all seems to end for them.
> >
> > Besides that i don't know if they do know what the problems with there
> > implementation in BIOS is when someone reports it.
> > I think some behind the scenes pressure from Intel to vendors might help to
> > solve some of them.
> > (my Q35 chipset, "Intel V-PRO" marketed motherboard (so much for that) also
> > suffers RMRR problem when another graphics card is inserted which switches off
> > the IGD).
> >
> > Although i think in my case your patch will work around that for me. Perhaps a
> > third option is needed, which does all the workarounds possible and warns
> > about potential security problem when requested ?
> >
> > --
> > Sander
> >
> >
> >
> >
> >
> >
> > Thursday, January 21, 2010, 1:46:39 PM, you wrote:
> >
> >     
> > > Noboru Iwamatsu wrote:
> > >       
> > > > Hi Weidong,
> > > >
> > > > I re-send the DRHD-fix patch.
> > > >
> > > > If DRHD does not have existent devices, ignore it.
> > > > If DRHD has both existent and non-existent devices, consider it invalid
> > > > and not register.
> > > >   
> > > >         
> > > Although you patch workarounds your buggy BIOS, but we still need to
> > > enable it for security purpose as I mentioned in previous mail. We
> > > needn't workaround / fix all BIOS issues in software. I think security
> > > is more important for this specific BIOS issue. Did you report the BIOS
> > > issue to your OEM vendor? maybe it's better to get it fixed in BIOS.
> > >       
> > > Regards,
> > > Weidong
> > >       
> > > > According to this patch and yours, my machine successfully booted
> > > > with vt-d enabled.
> > > >
> > > > Signed-off-by: Noboru Iwamatsu <n_iwamatsu@xxxxxxxxxxxxxx>
> > > >
> > > >
> > > >   
> > > >         
> > > > > Keir Fraser wrote:
> > > > >     
> > > > >           
> > > > > > On 21/01/2010 10:19, "Weidong Han" <weidong.han@xxxxxxxxx> wrote:
> > > > > >
> > > > > >       
> > > > > >             
> > > > > > > > Sorry this is typo.
> > > > > > > > I mean:
> > > > > > > > So, I think RMRR that has no-existent device is "invalid"
> > > > > > > > and whole RMRR should be ignored.
> > > > > > > >           
> > > > > > > >                 
> > > > > > > looks reasonable.
> > > > > > >
> > > > > > > Keir, I Acks Noboru's rmrr patch. Or do you want us to merge them to one
> > > > > > > patch?
> > > > > > >         
> > > > > > >               
> > > > > > Merge them up, re-send with both sign-off and acked-by all in one email.
> > > > > >
> > > > > > Thanks,
> > > > > > Keir
> > > > > >
> > > > > >       
> > > > > >             
> > > > > Sorry, I disagree with Noboru after thinking it again. If the RMRR has
> > > > > both no-existent device and also has existent devices in its scope, we
> > > > > should not ignore it because the existent devices under its scope will
> > > > > be impacted without the RMRR. so I suggest to print a warning instead of
> > > > > ignore it. Attached a patch for it.
> > > > >
> > > > > Signed-off-by: Weidong Han <weidong.han@xxxxxxxxx>
> > > > >     
> > > > >           
> > > >   
> > > >         
> >
> >     
>   
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