Re: [PATCH v2 0/8] x86/mtrr: fix handling with PAT but without MTRR

[Edgecombe, Rick P]

On Thu, 2023-02-09 at 08:22 +0100, Juergen Gross wrote:
> This series tries to fix the rather special case of PAT being
> available
> without having MTRRs (either due to CONFIG_MTRR being not set, or
> because the feature has been disabled e.g. by a hypervisor).

debug_vm_pgtable fails in a KVM guest with CONFIG_MTRR=y. CONFIG_MTRR=n
succeeds.

[    0.830280] debug_vm_pgtable: [debug_vm_pgtable         ]:
Validating architecture page table helpers
[    0.831906] ------------[ cut here ]------------
[    0.832711] WARNING: CPU: 0 PID: 1 at mm/debug_vm_pgtable.c:461
debug_vm_pgtable+0xb9a/0xe16
[    0.833998] Modules linked in:
[    0.834450] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 6.2.0-rc7+
#2366
[    0.835462] RIP: 0010:debug_vm_pgtable+0xb9a/0xe16
[    0.836217] Code: e2 3a 73 4a 48 c7 00 00 00 00 00 48 8b b4 24 a0 00
00 00 48 8b 54 24 60 48 8b 7c 24 20 48 c4
[    0.839068] RSP: 0000:ffffc90000013de0 EFLAGS: 00010246
[    0.839735] RAX: 0000000000000000 RBX: ffff888100048868 RCX:
bffffffffffffff0
[    0.840646] RDX: 0000000000000000 RSI: 0000000040000000 RDI:
0000000000000000
[    0.841661] RBP: ffff88810004d140 R08: 0000000000000000 R09:
ffff888100280880
[    0.842625] R10: 0000000000000001 R11: 0000000000000001 R12:
ffff888103810298
[    0.843574] R13: ffff888100048780 R14: ffffffff8282e099 R15:
0000000000000000
[    0.844524] FS:  0000000000000000(0000) GS:ffff88813bc00000(0000)
knlGS:0000000000000000
[    0.845706] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[    0.846499] CR2: ffff88813ffff000 CR3: 000000000222d001 CR4:
0000000000370ef0
[    0.847464] DR0: 0000000000000000 DR1: 0000000000000000 DR2:
0000000000000000
[    0.848432] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7:
0000000000000400
[    0.849371] Call Trace:
[    0.849699]  <TASK>
[    0.849997]  ? destroy_args+0x131/0x131
[    0.850487]  do_one_initcall+0x61/0x250
[    0.850983]  ? rdinit_setup+0x2c/0x2c
[    0.851451]  kernel_init_freeable+0x18e/0x1d8
[    0.852033]  ? rest_init+0x130/0x130
[    0.852533]  kernel_init+0x16/0x120
[    0.853035]  ret_from_fork+0x1f/0x30
[    0.853507]  </TASK>
[    0.853803] ---[ end trace 0000000000000000 ]---
[    0.854421] ------------[ cut here ]------------
[    0.855027] WARNING: CPU: 0 PID: 1 at mm/debug_vm_pgtable.c:462
debug_vm_pgtable+0xbaa/0xe16
[    0.856115] Modules linked in:
[    0.856517] CPU: 0 PID: 1 Comm: swapper/0 Tainted:
G        W          6.2.0-rc7+ #2366
[    0.857562] RIP: 0010:debug_vm_pgtable+0xbaa/0xe16
[    0.858186] Code: 00 00 00 48 8b 54 24 60 48 8b 7c 24 20 48 c1 e6 0c
e8 79 18 7f fe 85 c0 75 02 0f 0b 48 8b 7b
[    0.860778] RSP: 0000:ffffc90000013de0 EFLAGS: 00010246
[    0.861519] RAX: 0000000000000000 RBX: ffff888100048868 RCX:
bffffffffffffff0
[    0.862530] RDX: 0000000000000000 RSI: 0000000040000000 RDI:
ffff88810380e7f8
[    0.863522] RBP: ffff88810004d140 R08: 0000000000000000 R09:
ffff888100280880
[    0.864449] R10: 0000000000000001 R11: 0000000000000001 R12:
ffff888103810298
[    0.865454] R13: ffff888100048780 R14: ffffffff8282e099 R15:
0000000000000000
[    0.866401] FS:  0000000000000000(0000) GS:ffff88813bc00000(0000)
knlGS:0000000000000000
[    0.867438] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[    0.868181] CR2: ffff88813ffff000 CR3: 000000000222d001 CR4:
0000000000370ef0
[    0.869097] DR0: 0000000000000000 DR1: 0000000000000000 DR2:
0000000000000000
[    0.870026] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7:
0000000000000400
[    0.870943] Call Trace:
[    0.871259]  <TASK>
[    0.871537]  ? destroy_args+0x131/0x131
[    0.872030]  do_one_initcall+0x61/0x250
[    0.872521]  ? rdinit_setup+0x2c/0x2c
[    0.873005]  kernel_init_freeable+0x18e/0x1d8
[    0.873607]  ? rest_init+0x130/0x130
[    0.874116]  kernel_init+0x16/0x120
[    0.874618]  ret_from_fork+0x1f/0x30
[    0.875123]  </TASK>
[    0.875411] ---[ end trace 0000000000000000 ]---