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

[Weidong Han <weidong.han@xxxxxxxxx>]

Noboru Iwamatsu wrote:
>  > So, I think RMRR that has no-existent device is valid.
>
> 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?
Regards,
Weidong
> Noboru.
>
>   
> > Hi,
> >
> > After registered invalid DRHDs, Xen hangs in boot time.
> >
> > About RMRR, I understood the logic.
> > In my mainboard, unfortunately, RMRR has non-existent device under
> > its scope, and to make matters worse, the RMRR range is invalid.
> > So, I think RMRR that has no-existent device is valid.
> >
> > How do you think about these?
> >
> >     
> > > Hi Noboru,
> > >
> > > You should not ignore DRHD even if devices under its scope are not pci
> > > discoverable. For the sake of security, we still enable these DRHDs
> > > but don't set any context mappings. In that case, any DMA that comes
> > > from these "supposedly disabled" devices will get blocked by VT-d, and
> > > hence avoid any security vulnerability with malicious s/w re-enabling
> > > these devices.
> > >
> > > You RMRR validity fixing is wrong. My RMRR patch is no problem. Pls
> > > note that the RMRR checking logic is:
> > > If all devices under RMRR's scope are not pci discoverable
> > > Ignore the RMRR
> > > Else if base_address> end_address
> > > Return error
> > > Else
> > > Register RMRR
> > >
> > > Regards,
> > > Weidong
> > >
> > >
> > > -----Original Message-----
> > > From: Noboru Iwamatsu [mailto:n_iwamatsu@xxxxxxxxxxxxxx]
> > > Sent: Thursday, January 21, 2010 4:26 PM
> > > To: Han, Weidong
> > > Cc: xen-devel@xxxxxxxxxxxxxxxxxxx; keir.fraser@xxxxxxxxxxxxx
> > > Subject: Re: [Xen-devel] [PATCH] VT-d: improve RMRR validity checking
> > >
> > > Hi,
> > >
> > > Some Q35 mainboard that has buggy BIOS, I have one of this, reports
> > > invalid DRHD in addition to the invalid RMRR.
> > >
> > > Attached patch fixes this DRHD issue in the same way as RMRR.
> > > And also, I fixed RMRR validity checking loop.
> > >
> > > Noboru.
> > >
> > > Signed-off-by: Noboru Iwamatsu<n_iwamatsu@xxxxxxxxxxxxxx>
> > >
> > >
> > > -------- Original Message --------
> > > Subject: [Xen-devel] [PATCH] VT-d: improve RMRR validity checking
> > > From: Han, Weidong<weidong.han@xxxxxxxxx>
> > > To: xen-devel@xxxxxxxxxxxxxxxxxxx<xen-devel@xxxxxxxxxxxxxxxxxxx>
> > > Date: Thu Jan 21 2010 11:46:12 GMT+0900
> > >
> > >       
> > > > Currently, Xen checks RMRR range and disables VT-d if RMRR range is
> > > > set incorrectly in BIOS rigorously. But, actually we can ignore the
> > > > RMRR if the device under its scope are not pci discoverable, because
> > > > the RMRR won't be used by non-existed or disabled devices.
> > > >
> > > > This patch ignores the RMRR if the device under its scope are not pci
> > > > discoverable, and only checks the validity of RMRRs that are actually
> > > > used. In order to avoid duplicate pci device detection code, this
> > > > patch defines a function pci_device_detect for it.
> > > >
> > > > Signed-off-by: Weidong Han<weidong.han@xxxxxxxxx>
> > > >
> > > >
> > > >
> > > > _______________________________________________
> > > > Xen-devel mailing list
> > > > Xen-devel@xxxxxxxxxxxxxxxxxxx
> > > > http://lists.xensource.com/xen-devel
> > > >         
> > _______________________________________________
> > Xen-devel mailing list
> > Xen-devel@xxxxxxxxxxxxxxxxxxx
> > http://lists.xensource.com/xen-devel
> >     
>
>   

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