Hi, On Fri, Mar 04, 2022 at 08:43:03PM +0800, Huacai Chen wrote: > Hi, Mike, > > On Fri, Mar 4, 2022 at 6:49 PM Mike Rapoport <rppt@xxxxxxxxxx> wrote: > > > > Hi, > > > > > > So ideally, the physical memory detection and registration should follow > > something like: > > > > * memblock_reserve() the memory used by firmware, kernel and initrd > > * detect NUMA topology > > * add memory regions along with their node ids to memblock. > > > > s390::setup_arch() is a good example of doing early reservations: > > > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/s390/kernel/setup.c#n988 > I have a fast reading of S390, and I think we can do some adjust: > 1, call memblock_set_node(0, ULONG_MAX, &memblock.memory, 0) in > early_memblock_init(). > 2, move memblock_reserve(PHYS_OFFSET, 0x200000) and > memblock_reserve(__pa_symbol(&_text), __pa_symbol(&_end) - > __pa_symbol(&_text)) to early_memblock_init(). > 3, Reserve initrd memory in the first place. > It is nearly the same as the S390, then. It does not have to look like the same as s390 :) The important thing is to reserve all the memory before memblock allocations are possible. > > > > > +early_param("memmap", early_parse_memmap); > > > > > > > > The memmap= processing is a hack indented to workaround bugs in firmware > > > > related to the memory detection. Please don't copy if over unless there is > > > > really strong reason. > > > > > > Hmmm, I have read the documents, most archs only support mem=limit, > > > but MIPS support mem=limit@base. memmap not only supports > > > memmap=limit@base, but also a lot of advanced syntax. LoongArch needs > > > both limit and limit@base syntax. So can we make our code to support > > > only mem=limit and memmap=limit@base, and remove all other syntax > > > here? > > > > The documentation describes what was there historically and both these > > options tend not to play well with complex memory layouts. > > > > If you must have them it's better to use x86 as an example rather than > > MIPS, just take into the account that on x86 memory always starts from 0, > > so they never needed to have a different base. > > > > For what use-cases LoongArch needs options? > > The use-case of limit@base syntax is kdump, because our kernel is not > relocatable. I'll use X86 as an example. I missed that mem= can be used several times, so with MIPS implementation it's possible to define something like "mem=limit0@base0 mem=limit1@base1" and this will create two contiguous memory regions. > Huacai -- Sincerely yours, Mike.
