Re: [Xen-devel] [v3][PATCH 1/1] xen:vtd: missing RMRR mapping while share EPT

["Chen, Tiejun" <tiejun.chen@xxxxxxxxx>]

On 2014/7/25 15:07, Jan Beulich wrote:
> > > > On 25.07.14 at 08:48, <tiejun.chen@xxxxxxxxx> wrote:
> > On 2014/7/24 20:16, Jan Beulich wrote:
> > > > > > On 24.07.14 at 13:51, <tiejun.chen@xxxxxxxxx> wrote:
> > > > RMRR seems be used barely. Here in my case, just GFX passthrough needs
> > > > this since some windows GFX drivers may access those stolen memory now.
> > > USB legacy emulation is another use case iirc, as seen on at least
> > > one of the systems I have here.
> > >
> > > Furthermore an RMRR (as pointed out a couple of months ago)
> > I'm poor in this problem, so could you point where I can get this
> > discussion? I think I should take a look at that to know about more.
> http://lists.xenproject.org/archives/html/xen-devel/2014-02/msg00824.html
> (continued in March; the list server doesn't properly deal with
> cross-month follow-ups, so you'll need to search for the same
> subject in
> http://lists.xenproject.org/archives/html/xen-devel/2014-03/threads.html)
>
> > > may be related to more than one device (at least in theory), and
> > Are you saying one RMRR corresponds to multiple devfns?
> Yes, just look at acpi_parse_one_rmrr() and its helper
> acpi_parse_dev_scope(): There's nothing there enforcing just
> a single device per RMRR.
>
> > > in such case it is insecure to assign these devices to distinct
> > > domains.
> > But looks we always create one RMRR when an associated devfn is assigned
> > to one given domain, so this mean its always insecure before I introduce
> > this patch, right?
> If you meant "already" instead of "always", then yes. Your patch
> is just widening the issue.
Jan,

Such this kind of problem just happens in shared EPT case, right? In 
non-shared EPT case, we don't create these EPT tables to override other 
EPTs, so its okay?
Tiejun

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