Re: [PATCH 2/2] make /dev/kmem return error for highmem

[H. Peter Anvin]

On 02/08/2013 12:28 PM, Dave Hansen wrote:
> I was auding the /dev/mem code for more questionable uses of
> __pa(), and ran across this.
>
> My assumption is that if you use /dev/kmem, you expect to be
> able to read the kernel virtual mappings.  However, those
> mappings _stop_ as soon as we hit high memory.  The
> pfn_valid() check in here is good for memory holes, but since
> highmem pages are still valid, it does no good for those.
>
> Also, since we are now checking that __pa() is being done on
> valid virtual addresses, this might have tripped the new
> check.  Even with the new check, this code would have been
> broken with the NUMA remapping code had we not ripped it
> out:

It would be great if you could take a stab at fixing /dev/mem and 
/dev/kmem... there are a bunch of problems with both which seem to 
really translate to "HIGHMEM was never properly implemented"...

	-hpa


--
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

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