Messages in this thread | | | Date | Fri, 05 Oct 2012 09:28:00 -0700 | From | "H. Peter Anvin" <> | Subject | Re: [PATCH 1/3] x86, mm: Include the entire kernel memory map in trampoline_pgd |
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On 10/04/2012 11:39 PM, Jan Beulich wrote: >> >> We should have the check, but at least for Linux support we require >> P <= V-2. > > Not really imo - P <= V - 1 should be sufficient here, as all that is > necessary is that the result represents a 1:1 mapping. Specifically, > there's no constraint to the virtual space limitation of the direct > mapping of RAM. >
The P <= V-2 limitation doesn't come from this, it comes from the fact that we need to have the regular kernel 1:1 map and still have space for the kernel, vmalloc, ioremap and so on in the kernel part of the address space; in theory it *could* be some fraction between 1 and 2, but since hardware doesn't do fractional bits very well the above is what we have been telling the hardware folks. :)
-hpa -- H. Peter Anvin, Intel Open Source Technology Center I work for Intel. I don't speak on their behalf.
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