On Wed, 2011-06-15 at 10:30 +0100, David Laight wrote: > > The PPC440X currently uses 256M TLB entries to pin the > > lowmem. When we go for a relocatable kernel we have to : > > > > 1) Restrict the kernel load address to be 256M aligned > > > > OR > > > > 2) Use 16M TLB(the next possible TLB page size supported) > > entries till the first > > 256M and then use the 256M TLB entries for the rest of lowmem. > > What is wrong with: > > 3) Use 256M TLB entries with the lowest one including > addresses below the kernel base. > > Clearly the kernel shouldn't be accessing the addresses > below its base address - but that is true of a lot of > address space mapped into the kernel.
In the case of a relocatable kernel it's perfectly kosher to access addresses below the kernel itself... Typically this is used for kdump where the kdump kernel excecutes in place in a reserved area but access to the rest of memory is allowed to ... well, do the dump :-) There could be other reasons to do that too. Cheers, Ben. _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
