On 08/18/2014 10:48 PM, Toshi Kani wrote: > On Sun, 2014-08-17 at 12:17 +0300, Boaz Harrosh wrote: <> >> "System RAM" it is not. > > I think add_memory() can be easily extended (or modified to provide a > separate interface) for persistent memory, and avoid creating the sysfs > interface and change the handling with firmware_map. But I can also see > your point that persistent memory should not be added to zone at all. > Right > Anyway, I am a bit concerned with the way to create direct mappings with > map_vm_area() within the prd driver. Can we use init_memory_mapping() > as it's used by add_memory() and supports large page size? The size of > persistent memory will grow up quickly. A bit about large page size. The principal reason of my effort here is that at some stage I need to send pmem blocks to block-layer or network. The PAGE == 4K is pasted all over the block stack. Do you know how those can work together? will we need some kind of page_split thing how does that work? > Also, I'd prefer to have an mm > interface that takes care of page allocations and mappings, and avoid a > driver to deal with them. > This is a great idea you mean that I define: + int mm_add_page_mapping(phys_addr_t phys_addr, size_t total_size, + void **o_virt_addr) At the mm level. OK It needs a much better name. I know of 2 more drivers that will need the use of the same interface actually, so you are absolutely right. I didn't dare ask ;-) >> And also I think that for DDR4 NvDIMMs we will fail with: >> ret = check_hotplug_memory_range(start, size); >> > > Can you elaborate why DDR4 will fail with the function above? > I'm not at all familiar with the details, perhaps the Intel guys that knows better can chip in, but from the little I understood: Today with DDR3 these chips come up at the e820 controller, as type 12 memory and, each vendor has a driver to drive proprietary enablement and persistence. With DDR4 it will all be standardized, but it will not come up through the e820 manager, but as a separate device on the SMBus/ACPI. So it is not clear to me that we want to plug this back into the ARCH's memory controllers. check_hotplug_memory_range is it per ARCH? > Thanks, > -Toshi > > I will produce a new Patchset that introduces a new API for drivers. And I will try to see about the use of init_memory_mapping(), as long as it is not using zones. Do you think that the new code should sit in? mm/memory_hotplug.c Thanks Boaz -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>