quoted

The stack track is in mm/page_alloc.c. I've done a little
investigation, but I can't account for why there's a hard cutoff of
correctness at 256GB

[    0.065563] RIP: 0010:memmap_init_range+0x108/0x173
[    0.066309] Code: 77 16 f6 42 10 02 74 10 48 03 42 08 48 c1 e8 0c
48 89 c3 e9 3a ff ff ff 48 89 df 48 c1 e7 06 48 03 3d d9 a2 66 ff 48
8d 47 08 <c7> 47 34 01 00 00 00 48 c7 47 38 00 00 00 00 c7 47 30 ff ff
ff ff
[    0.069108] RSP: 0000:ffffffffad603dc8 EFLAGS: 00010082 ORIG_RAX:
0000000000000404
[    0.070193] RAX: ffffdba740000048 RBX: 0000000000000001 RCX: 0000000000000000
[    0.071170] RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffdba740000040
[    0.072224] RBP: 0000000000000000 R08: 0000000000001000 R09: 0000000000000000
[    0.073283] R10: 0000000000000001 R11: ffffffffad645c60 R12: 0000000000000000
[    0.074304] R13: 00000000000000a0 R14: 0000000000000000 R15: 0000000000000000
[    0.075285] FS:  0000000000000000(0000) GS:ffffffffadd6c000(0000)
knlGS:0000000000000000
[    0.076365] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[    0.077194] CR2: ffffdba740000074 CR3: 0008001ee3a0c000 CR4: 00000000000606b0
[    0.078209] Call Trace:
[    0.078524]  <TASK>
[    0.078887]  ? free_area_init+0x5c1/0x66c
[    0.079417]  ? zone_sizes_init+0x52/0x6c
[    0.079934]  ? setup_arch+0xa55/0xb6d
[    0.080417]  ? start_kernel+0x64/0x65a
[    0.080897]  ? secondary_startup_64_no_verify+0xd6/0xdb
[    0.081620]  </TASK>

Note that there is a bug in Brijesh's version of the patch and it will
almost exclusively use the MSR protocol. Please try the version of the
patch that I recently sent up based on the current unaccepted memory tree
from Kirill.

I've now tested this patch set with Tom's new patch set, and it
appears to be that the problem with 256GB is more likely to be due to
this unaccepted memory patch set rather than something AMD-specific.

Kirill, do you see any problems with 256GB on TDX? It seems there is
some unaccepted memory getting touched in memmap_init_range when the
VM's memory size is at least 256GB

-- 
-Dionna Glaze, PhD (she/her)