Re: [Xen-devel] [PATCH] xen/x86: Force removal of memory range when not covered by MTRRs

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

On Fri, Feb 15, 2013 at 02:52:41PM +0000, Jan Beulich wrote:
> >>> On 15.02.13 at 14:47, Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx> 
> >>> wrote:
> >> >> Since when is E820_UNUSABLE memory being used as guest
> >> >> memory? If that's indeed the case, that's the bug to fix. The
> >> >> above data to me shows, however, that the range above
> >> >> 228000000 is considered invalid. So then the question is why the
> >> >> kernel tries to map that memory in the first place (the hypervisor
> >> >> rejecting the attempt, despite Dom0 being privileged, seems
> >> >> correct to me, as the range is also known not to be MMIO).
> > 
> > B/c it gets the E820 from the hypervisor, which shows that area as
> > E820_UNUSABLE. And dom0 (or rather, the generic memory code) ends up
> > creating pagetables for it.
> 
> That would be wrong even on native, and I don't see how that
> would happen: memblock_add() gets called from
> memblock_x86_fill() only for E820_RAM and E820_RESERVED_KERN
> ranges.

Hm, the bug report shows that the ranges (which are E820_UNUSABLE)
do get called with init_memory_mapping.

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