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Roger Pau Monne
c5c45bcbd6
With the appearance of Intel Sierra Forest and Granite Rapids it's now possible to get a production x86 host with the following memory map: SRAT: Node 0 PXM 0 [0000000000000000, 000000007fffffff] SRAT: Node 0 PXM 0 [0000000100000000, 000000807fffffff] SRAT: Node 1 PXM 1 [0000063e80000000, 000006be7fffffff] SRAT: Node 2 PXM 2 [00000c7e80000000, 00000cfe7fffffff] SRAT: Node 3 PXM 3 [000012be80000000, 0000133e7fffffff] This is from a four socket Granite Rapids system, with each node having 512GB of memory. The total amount of RAM on the system is 2TB, but without enabling CONFIG_BIGMEM the last range is not accessible, as it's above the 16TB boundary covered by the frame table. Sierra Forest and Granite Rapids are socket compatible, however Sierra Forest only supports 2 socket configurations, while Granite Rapids can go up to 8 sockets. Note that while the memory map is very sparse, it couldn't be compressed using the current PDX_MASK compression algorithm, which relies on all ranges having a shared zeroed region of bits that can be removed. The memory map presented above has the property of all regions being similarly spaced between each other, and all having also a similar size. Use a lookup table to store the offsets to translate from/to PFN and PDX spaces. Such table is indexed based on the input PFN or PDX to translated. The example PFN layout about would get compressed using the following: PFN compression using PFN lookup table shift 29 and PDX region size 0x10000000 range 0 [0000000000000, 0x0000807ffff] PFN IDX 0 : 0000000000000 range 1 [0x00063e80000, 0x0006be7ffff] PFN IDX 3 : 0x00053e80000 range 2 [0x000c7e80000, 0x000cfe7ffff] PFN IDX 6 : 0x000a7e80000 range 3 [0x0012be80000, 0x00133e7ffff] PFN IDX 9 : 0x000fbe80000 Note how the tow ranges belonging to node 0 get merged into a single PDX region by the compression algorithm. The default size of lookup tables currently set in Kconfig is 64 entries, and the example memory map consumes 10 entries. Such memory map is from a 4 socket Granite Rapids host, which in theory supports up to 8 sockets according to Intel documentation. Assuming the layout of a 8 socket system is similar to the 4 socket one, it would require 21 lookup table entries to support it, way below the current default of 64 entries. The valid range of lookup table size is currently restricted from 1 to 512 elements in Kconfig. An extra array is used to keep track of the base PFN for each translated range. Non used slots are set to ~0UL, so that in mfn_valid() the mfn < base check always fails, thus reporting the mfn as invalid. Introduce __init_or_pdx_mask and use it on some shared functions between PDX mask and offset compression, as otherwise some code becomes unreachable after boot if PDX offset compression is used. Mark the code as __init in that case, so it's pruned after boot. Signed-off-by: Roger Pau Monné <roger.pau@citrix.com> Reviewed-by: Jan Beulich <jbeulich@suse.com>