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

[Noboru Iwamatsu <n_iwamatsu@xxxxxxxxxxxxxx>]

> 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.

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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