arm64: Set ATTR_CONTIGUOUS on the kernel code and data sections when the page size is 16K

[alc]

Summary

When the page size is 16K, map the kernel code and data sections using 2M pages. Previously, they were mapped using 16K pages.

Test Plan

Before:

vm.pmap.kernel_maps:
Kernel map:
0xffff000000000000-0xffff0000014b4000 rwx-sg     WB 0 0 0 1325
0xffff0000014b4000-0xffff0000014c4000 r---sg     WB 0 0 0 4
0xffff0000014c4000-0xffff0000014d0000 rwx-sg     WB 0 0 0 3
0xffff0000014d0000-0xffff0000014ec000 r-x-sg     WB 0 0 0 7
0xffff0000014ec000-0xffff0000014f4000 rwx-sg     WB 0 0 0 2
0xffff0000014f4000-0xffff0000014fc000 rw--sg     WB 0 0 0 2
0xffff0000014fc000-0xffff000001b40000 rwx-sg     WB 0 0 0 401
0xffff001002000000-0xffff001002010000 r---sg     WB 0 0 0 4
0xffff001002010000-0xffff0010020e8000 rw--sg     WB 0 0 0 54
0xffff0010020e8000-0xffff0010020f8000 rw--sg    DEV 0 0 0 4
0xffff0010020f8000-0xffff0010021f8000 rw--sg     WT 0 0 0 64
0xffff0010021f8000-0xffff0010021fc000 rw--sg     WB 0 0 0 1
0xffff001002200000-0xffff001003200000 rw--sg DEV-NP 0 0 8 0
0xffff001003f34000-0xffff001003f74000 rw--sg     WB 0 0 0 16
0xffff001004000000-0xffff00100a000000 rw--sg     WB 0 1 15 2176

After:

vm.pmap.kernel_maps: 
Kernel map:
0xffff000000000000-0xffff0000014b4000 rwx-sg     WB 0 0 10 45
0xffff0000014b4000-0xffff0000014c4000 r---sg     WB 0 0 0 4
0xffff0000014c4000-0xffff0000014d0000 rwx-sg     WB 0 0 0 3
0xffff0000014d0000-0xffff0000014ec000 r-x-sg     WB 0 0 0 7
0xffff0000014ec000-0xffff0000014f4000 rwx-sg     WB 0 0 0 2
0xffff0000014f4000-0xffff0000014fc000 rw--sg     WB 0 0 0 2
0xffff0000014fc000-0xffff000001b40000 rwx-sg     WB 0 0 2 145
0xffff001002000000-0xffff001002010000 r---sg     WB 0 0 0 4
0xffff001002010000-0xffff0010020e8000 rw--sg     WB 0 0 0 54
0xffff0010020e8000-0xffff0010020f8000 rw--sg    DEV 0 0 0 4
0xffff0010020f8000-0xffff0010021f8000 rw--sg     WT 0 0 0 64
0xffff0010021f8000-0xffff0010021fc000 rw--sg     WB 0 0 0 1
0xffff001002200000-0xffff001003200000 rw--sg DEV-NP 0 0 8 0
0xffff001003f34000-0xffff001003f74000 rw--sg     WB 0 0 0 16
0xffff001004000000-0xffff00100a000000 rw--sg     WB 0 1 15 2176

[markj]

On an Altra with this patch I see:

Kernel map:
0xffff000000000000-0xffff0000013e4000 rwx-sg     WB 0 0 9 121
0xffff0000013e4000-0xffff0000014d8000 r---sg     WB 0 0 0 61
0xffff0000014d8000-0xffff0000014e0000 rwx-sg     WB 0 0 0 2
0xffff0000014e0000-0xffff000001738000 r-x-sg     WB 0 0 0 150
0xffff000001738000-0xffff000001740000 rwx-sg     WB 0 0 0 2
0xffff000001740000-0xffff000001820000 rw--sg     WB 0 0 0 56
0xffff000001820000-0xffff000001f98000 rwx-sg     WB 0 0 2 222
0xffff001002000000-0xffff001002010000 r---sg     WB 0 0 0 4

sys/arm64/arm64/locore.S

813

It might be worth commenting here or at the beginning of the subroutine that we're making an assumption about the alignment of PA and VA here.

[alc]

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