Re: [PATCHv7 02/14] mm: Add support for unaccepted memory

Dionna Amalie Glaze
2022-09-06T17:50:56Z

>
> It really helps this kind of stuff if you can post the *actual* error.
> I assume this was a page fault, so there should have been some other
> stuff before the RIP:...
>

I posted the error on August 15th. I was bumping in my last post
since I confirmed with Tom Lendacky that it wasn't AMD's patches at
fault.
Here's a new dump below that matches the disassembly:

[ 0.043137] Faking a node at [mem 0x0000000000000000-0x000000403fffffff]
[ 0.044018] NODE_DATA(0) allocated [mem 0x403fffc000-0x403fffffff]
[ 0.044922] Zone ranges:
[ 0.045250] DMA [mem 0x0000000000001000-0x0000000000ffffff]
[ 0.046039] DMA32 [mem 0x0000000001000000-0x00000000ffffffff]
[ 0.046828] Normal [mem 0x0000000100000000-0x000000403fffffff]
[ 0.047657] Movable zone start for each node
[ 0.048201] Early memory node ranges
[ 0.048674] node 0: [mem 0x0000000000001000-0x000000000009ffff]
[ 0.049474] node 0: [mem 0x0000000000100000-0x000000000080cfff
[ 0.050274] node 0: [mem 0x000000000080f000-0x00000000beceefff]
[ 0.051074] node 0: [mem 0x00000000befff000-0x00000000bfbb0fff]
[ 0.051874] node 0: [mem 0x00000000bfbb2000-0x00000000bffdbfff]
[ 0.052674] node 0: [mem 0x0000000100000000-0x000000403fffffff]
[ 0.053530] Initmem setup node 0 [mem 0x0000000000001000-0x000000403fffffff]
PANIC: Unsupported exit-code 0x404 in early #VC exception (IP:
0xfffffffface0cdd0)
[ 0.056667] CPU: 0 PID: 0 Comm: swapper Not tainted
5.17.0-rc6-173762-gffb12b02c6d7-dirty #1
[ 0.057744] Hardware name: Google Google Compute Engine/Google
Compute Engine, BIOS Google 01/01/2011
[ 0.058920] RIP: 0010:memmap_init_range+0x11d/0x188
[ 0.059686] 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 a4 1e 65 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
[ 0.062121] RSP: 0000:ffffffffac603dc0 EFLAGS: 00010082 ORIG_RAX:
0000000000000404
[ 0.063087] RAX: ffffda1ac0000048 RBX: 0000000000000001 RCX: 0000000000000000
[ 0.063998] RDX: 0300000000000000 RSI: 0000000000000000 RDI: ffffda1ac000004
[ 0.064944] RBP: 0000000000000000 R08: 0000000000001000 R09: 0000000000000000
[ 0.065873] R10: 0000000000000001 R11: 0000000000000000 R12: 0000000000000000
[ 0.066782] R13: 00000000000000a0 R14: 0000000000000000 R15: 0000000000000000
[ 0.067695] FS: 0000000000000000(0000) GS:ffffffffacd88000(0000)
knlGS:0000000000000000
[ 0.068727] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 0.069488] CR2: ffffda1ac0000074 CR3: 00080020b680c000 CR4: 00000000000606b0
[ 0.070397] Call Trace:
[ 0.070710] <TASK>
[ 0.070976] ? free_area_init+0x724/0x7d4
[ 0.071486] ? zone_sizes_init+0x52/0x6c
[ 0.071986] ? setup_arch+0xa55/0xb77
[ 0.072453] ? start_kernel+0x64/0x65f
[ 0.072931] ? secondary_startup_64_no_verify+0xd6/0xdb
[ 0.073598] </TASK>

Note this is a crash in SEV-SNP, but I assume we'd get the same #VE in TDX.

> Another thing that's really nice is to do the disassembly of the "Code:"
> or share disassembly of memmap_init_range.

0000000000000172 <memmap_init_range>:
172: 41 56 push %r14
174: 89 f0 mov %esi,%eax
176: 45 89 ce mov %r9d,%r14d
179: 41 55 push %r13
17b: 4c 8d 2c 39 lea (%rcx,%rdi,1),%r13
17f: 41 54 push %r12
181: 49 89 d4 mov %rdx,%r12
184: 49 8d 55 ff lea -0x1(%r13),%rdx
188: 48 3b 15 00 00 00 00 cmp 0x0(%rip),%rdx # 18f
<memmap_init_range+0x1d>
18f: 55 push %rbp
190: 53 push %rbx
191: 48 89 cb mov %rcx,%rbx
194: 76 07 jbe 19d <memmap_init_range+0x2b>
196: 48 89 15 00 00 00 00 mov %rdx,0x0(%rip) # 19d
<memmap_init_range+0x2b>
19d: 4c 89 e5 mov %r12,%rbp
1a0: ba 03 00 00 00 mov $0x3,%edx
1a5: 48 c1 e0 3a shl $0x3a,%rax
1a9: 48 c1 e5 38 shl $0x38,%rbp
1ad: 48 c1 e2 38 shl $0x38,%rdx
1b1: 48 21 d5 and %rdx,%rbp
1b4: 48 09 c5 or %rax,%rbp
1b7: 49 39 dd cmp %rbx,%r13
1ba: 0f 86 31 01 00 00 jbe 2f1 <memmap_init_range+0x17f>
1c0: 45 85 f6 test %r14d,%r14d
1c3: 0f 85 b4 00 00 00 jne 27d <memmap_init_range+0x10b>
1c9: 49 83 fc 03 cmp $0x3,%r12
1cd: 0f 94 c1 sete %cl
1d0: 22 0d 00 00 00 00 and 0x0(%rip),%cl # 1d6
<memmap_init_range+0x64>
1d6: 0f 84 a1 00 00 00 je 27d <memmap_init_range+0x10b>
1dc: 48 8b 15 00 00 00 00 mov 0x0(%rip),%rdx # 1e3
<memmap_init_range+0x71>
1e3: 48 85 d2 test %rdx,%rdx
1e6: 74 10 je 1f8 <memmap_init_range+0x86>
1e8: 48 8b 42 08 mov 0x8(%rdx),%rax
1ec: 48 03 02 add (%rdx),%rax
1ef: 48 c1 e8 0c shr $0xc,%rax
1f3: 48 39 d8 cmp %rbx,%rax
1f6: 77 55 ja 24d <memmap_init_range+0xdb>
1f8: 48 8b 05 00 00 00 00 mov 0x0(%rip),%rax # 1ff
<memmap_init_range+0x8d>
1ff: 4c 6b 05 00 00 00 00 imul $0x18,0x0(%rip),%r8 #
207 <memmap_init_range+0x95>
206: 18
207: 31 f6 xor %esi,%esi
209: 48 89 05 00 00 00 00 mov %rax,0x0(%rip) # 210
<memmap_init_range+0x9e>
210: 49 01 c0 add %rax,%r8
213: 48 89 c7 mov %rax,%rdi
216: 4c 39 c0 cmp %r8,%rax
219: 73 26 jae 241 <memmap_init_range+0xcf>
21b: 48 8b 57 08 mov 0x8(%rdi),%rdx
21f: 48 03 17 add (%rdi),%rdx
222: 48 83 c0 18 add $0x18,%rax
226: 48 c1 ea 0c shr $0xc,%rdx
22a: 48 39 da cmp %rbx,%rdx
22d: 76 0e jbe 23d <memmap_init_range+0xcb>
22f: 40 84 f6 test %sil,%sil
232: 74 19 je 24d <memmap_init_range+0xdb>
234: 48 89 3d 00 00 00 00 mov %rdi,0x0(%rip) # 23b
<memmap_init_range+0xc9>
23b: eb 10 jmp 24d <memmap_init_range+0xdb>
23d: 89 ce mov %ecx,%esi
23f: eb d2 jmp 213 <memmap_init_range+0xa1>
241: 40 84 f6 test %sil,%sil
244: 74 07 je 24d <memmap_init_range+0xdb>
246: 48 89 05 00 00 00 00 mov %rax,0x0(%rip) # 24d
<memmap_init_range+0xdb>
24d: 48 8b 15 00 00 00 00 mov 0x0(%rip),%rdx # 254
<memmap_init_range+0xe2>
254: 48 8b 02 mov (%rdx),%rax
257: 48 8d 88 ff 0f 00 00 lea 0xfff(%rax),%rcx
25e: 48 c1 e9 0c shr $0xc,%rcx
262: 48 39 d9 cmp %rbx,%rcx
265: 77 16 ja 27d <memmap_init_range+0x10b>
267: f6 42 10 02 testb $0x2,0x10(%rdx)
26b: 74 10 je 27d <memmap_init_range+0x10b>
26d: 48 03 42 08 add 0x8(%rdx),%rax
271: 48 c1 e8 0c shr $0xc,%rax
275: 48 89 c3 mov %rax,%rbx
278: e9 3a ff ff ff jmp 1b7 <memmap_init_range+0x45>
27d: 48 89 df mov %rbx,%rdi
280: 48 c1 e7 06 shl $0x6,%rdi
284: 48 03 3d 00 00 00 00 add 0x0(%rip),%rdi # 28b
<memmap_init_range+0x119>
28b: 48 8d 47 08 lea 0x8(%rdi),%rax
28f: c7 47 34 01 00 00 00 movl $0x1,0x34(%rdi) # Here's
where the crash RIP is.
296: 48 c7 47 38 00 00 00 movq $0x0,0x38(%rdi)
29d: 00
29e: c7 47 30 ff ff ff ff movl $0xffffffff,0x30(%rdi)
2a5: 48 c7 47 28 00 00 00 movq $0x0,0x28(%rdi)
2ac: 00
2ad: 48 c7 47 20 00 00 00 movq $0x0,0x20(%rdi)
2b4: 00
2b5: 48 c7 47 18 00 00 00 movq $0x0,0x18(%rdi)
2bc: 00
2bd: 48 89 2f mov %rbp,(%rdi)
2c0: 48 89 47 08 mov %rax,0x8(%rdi)
2c4: 48 89 47 10 mov %rax,0x10(%rdi)
2c8: 41 83 fe 01 cmp $0x1,%r14d
2cc: 75 05 jne 2d3 <memmap_init_range+0x161>
2ce: 48 0f ba 2f 0c btsq $0xc,(%rdi)
2d3: f7 c3 ff 01 00 00 test $0x1ff,%ebx
2d9: 75 0e jne 2e9 <memmap_init_range+0x177>
2db: 8b 74 24 38 mov 0x38(%rsp),%esi
2df: e8 00 00 00 00 call 2e4 <memmap_init_range+0x172>
2e4: e8 00 00 00 00 call 2e9 <memmap_init_range+0x177>
2e9: 48 ff c3 inc %rbx
2ec: e9 c6 fe ff ff jmp 1b7 <memmap_init_range+0x45>
2f1: 5b pop %rbx
2f2: 5d pop %rbp
2f3: 41 5c pop %r12
2f5: 41 5d pop %r13
2f7: 41 5e pop %r14
2f9: c3 ret

> Even nicer would be to give
> an faddr2line of the RIP value and track down which C code was actually
> at fault.

arch_atomic_set
arch/x86/include/asm/atomic.h:41

of INIT_LIST_HEAD in __init_single_page, called from memmap_init_range.
--
-Dionna Glaze, PhD (she/her)