RE: [Xen-devel] Critical bug: VT-d fault causes disk corruption or Dom0 kernel panic.

["Cihula, Joseph" <joseph.cihula@xxxxxxxxx>]

> From: Kay, Allen M
> Sent: Friday, January 23, 2009 3:40 PM
>
> I talked to Joe Cihula about this.  He is suggesting map only the RAM memory 
> in E820 table.
> This is more secure than map everything below max_page.  We can do this for 
> x86_64 and x86_32.
> For IA-64, we still map everything below max_page as there is no tboot issue.
>
> What do you think of is approach?
>
> Allen

But excluding the Xen text sections using is_kernel_text().

Joe

>
> -----Original Message-----
> From: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx 
> [mailto:xen-devel-bounces@xxxxxxxxxxxxxxxxxxx] On
> Behalf Of Keir Fraser
> Sent: Friday, January 23, 2009 10:44 AM
> To: Kay, Allen M; Li, Xin; Li, Haicheng; 'xen-devel@xxxxxxxxxxxxxxxxxxx'
> Subject: Re: [Xen-devel] Critical bug: VT-d fault causes disk corruption or 
> Dom0 kernel panic.
>
> On 23/01/2009 18:41, "Keir Fraser" <keir.fraser@xxxxxxxxxxxxx> wrote:
>
> > Also it's going to be hard to do better while keeping efficiency since if 
> > you
> > only map dom0's pages in its vtd tables then PV backend drivers will not 
> > work
> > (which rely on DMAing to/from other domain's pages via grant references).
> > You'd have to dynamically map/unmap as grants get mapped/unmapped, and you 
> > may
> > not want the performance hit of that.
> >
> > I'd personally vote for getting rid of xen_in_range(). Alternatively we 
> > could
> > have it merely check for is_kernel_text(), but really I think since it is 
> > not
> > in any way full protection from dom0 I wonder if it is worth the bother at
> > all.
> >
> > What do you think?
>
> I should add that you could still implement the more sophisticated and
> slower full protection, where dom0 only has DMA access to pages it currently
> has access to via the host CPUs, as a boot option. For those who really
> don't want to trust dom0 as far as possible.
>
>  -- Keir
>
>
>
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