Messages in this thread | | | Date | Tue, 19 Mar 2013 14:54:24 -0700 | From | Andrew Morton <> | Subject | Re: gen_pool_add broken with LPAE based systems |
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On Thu, 14 Mar 2013 16:05:27 -0700 Laura Abbott <lauraa@codeaurora.org> wrote:
> Hi, > > We use genalloc for managing certain pools of physical memory. genalloc > currently uses unsigned long for virtual addresses and phys_addr_t for > physical addresses. Our ARM LPAE systems have 64-bit physical addresses > but unsigned long is still 32 bits. Using gen_pool_add breaks with > addresses > 4G because gen_pool_add treats the address passed in as the > virtual address. gen_pool allocates internally based on the 32 bit > virtual address as well so everything is broken if we want to be able to > manage the full address space after 4G. I see a couple of options:
The above only makes sense if ARM LPAE has 64-bit (actually >= 33-bit) virtual addresses. If so, I don't understand how ARM LPAE can work at all - the core MM assumes that addresses-fit-in-ulongs in eleventy trillion places.
I think we need a better description of the problem, please.
> 1) Change gen_pool_add to use physical addresses and allocate based on > physical addresses instead of virtual addresses > 2) Change the virtual address to be a 64 bit type or something > selectable to a 64 bit type. > 3) Allow a flag per pool to select whether the allocator is virtual or > physical and switch between those. > 4) Split the APIs into virtual <-> physical and physical only and have > separate types for each. > > Any of these suggestions seem reasonable or is there another option to > consider?
2) sounds least intrusive but I can't think with my head spinning so fast.
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