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SubjectRe: [PATCHv7 02/14] mm: Add support for unaccepted memory
On Tue, Sep 06, 2022 at 10:50:42AM -0700, Dionna Amalie Glaze wrote:
> >
> > 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.

Looks like the first access to the memory map fails, although I think
it's not in INIT_LIST_HEAD() but rather in init_page_count().

I'd start with making sure that page_alloc::memmap_alloc() actually returns
accepted memory. If you build kernel with CONFIG_DEBUG_VM=y the memory map
will poisoned in this function, so my guess is it'd crash there.

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

--
Sincerely yours,
Mike.

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