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

[Weidong Han <weidong.han@xxxxxxxxx>]

Andrew Lyon wrote:
> On Thu, Jan 21, 2010 at 8:25 AM, Noboru Iwamatsu
> <n_iwamatsu@xxxxxxxxxxxxxx> wrote:
>   
> > 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
> >
> >
> >     
> I have a Supermicro X7DWA-N system which requires
> iommu_inclusive_mapping=1 in order to boot Xen successfully with iommu
> enabled, I am going to try these patches to see if the workaround is
> still necessary but I would also like to ask for some help in getting
> the bios fixed properly , I contacted Supermicro about this issue last
> year and they said they would fix it but they wanted details of
> exactly what was wrong, I tried to figure it out by using acpidump and
> reading the rmrr spec but I failed to make sense of it, perhaps you
> could have a quick look at this dump and let me know if there is
> anything obviously wrong?
>  
>   
iommu_inclusive_mapping=1 workarounds another problem. These code in Xen just 
makes Xen more defensive to BIOS errors. The final solution is to get them 
fixed in BIOS.

Regards,
Weidong


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