Greg, On 9/12/2012 2:15 PM, Greg KH wrote:
On Wed, Sep 12, 2012 at 02:05:58PM -0400, Cyril Chemparathy wrote:This patch fixes the /dev/mem driver to use phys_addr_t for physical addresses. This is required on PAE systems, especially those that run entirely out of >4G physical memory space.What is the symptom if this patch is not applied? Does it need to be backported to older kernels? If so, which ones?
As far as I can tell, this change only benefits platforms where lowmem lies outside the 32-bit addressable range. On the ARM based KeyStone platform, all of our memory is located above the 4GB limit at 0x8:0000:0000. On this platform, trying to read lowmem breaks as follows:
# dd if==/dev/mem of=/dev/null bs==4k count=1 skip=8388608 dd: /dev/mem: Bad addressAssuming that we are unique in this regard (i.e. lowmem outside 4GB), I don't see any reason to backport this to earlier kernels.
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