Re: [Xen-devel] [PATCH 1/3] x86: don't allow Dom0 access to the MSI address range

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Wed, Aug 21, 2013 at 03:44:09PM +0100, Jan Beulich wrote:
> >>> On 21.08.13 at 16:29, Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx> 
> >>> wrote:
> > On Wed, Aug 21, 2013 at 07:36:58AM +0100, Jan Beulich wrote:
> >> In particular, MMIO assignments should not be done using this area.
> > 
> > And just to make sure there are no regressions - have you tested
> > this with an upstream dom0 kernel to make sure it does not blow things up?
> 
> No, I didn't. I'm only testing with our own kernels. But I can't see
> how this could cause any regression - Dom0 is not supposed to
> map that page (from CPU perspective it's the LAPIC) one, and if
> it ever assigned the range as MMIO to a device, things would have
> blown up.

I see. What an odd name for an LAPIC region - MMIO.
> 
> > Or at least if it does blow up - are there any WARN or BUG to help
> > in coming up with a patch?
> 
> The E820 machine memory map that Dom0 gets to see would
> have that range marked as reserved (or unusable), and the
> MMIO rangeset printed in 'q' debug key output would also show
> the page as not accessible.

Thank you.
> 
> Jan
> 

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