CVE-2026-31601: vfio/xe: Reorganize the init to decouple migration from reset
In the Linux kernel, the following vulnerability has been resolved:

vfio/xe: Reorganize the init to decouple migration from reset

Attempting to issue reset on VF devices that don't support migration
leads to the following:

  BUG: unable to handle page fault for address: 00000000000011f8
  #PF: supervisor read access in kernel mode
  #PF: error_code(0x0000) - not-present page
  PGD 0 P4D 0
  Oops: Oops: 0000 [#1] SMP NOPTI
  CPU: 2 UID: 0 PID: 7443 Comm: xe_sriov_flr Tainted: G S   U              7.0.0-rc1-lgci-xe-xe-4588-cec43d5c2696af219-nodebug+ #1 PREEMPT(lazy)
  Tainted: [S]=CPU_OUT_OF_SPEC, [U]=USER
  Hardware name: Intel Corporation Alder Lake Client Platform/AlderLake-P DDR4 RVP, BIOS RPLPFWI1.R00.4035.A00.2301200723 01/20/2023
  RIP: 0010:xe_sriov_vfio_wait_flr_done+0xc/0x80 [xe]
  Code: ff c3 cc cc cc cc 0f 1f 84 00 00 00 00 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 0f 1f 44 00 00 55 48 89 e5 41 54 53 <83> bf f8 11 00 00 02 75 61 41 89 f4 85 f6 74 52 48 8b 47 08 48 89
  RSP: 0018:ffffc9000f7c39b8 EFLAGS: 00010202
  RAX: ffffffffa04d8660 RBX: ffff88813e3e4000 RCX: 0000000000000000
  RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
  RBP: ffffc9000f7c39c8 R08: 0000000000000000 R09: 0000000000000000
  R10: 0000000000000000 R11: 0000000000000000 R12: ffff888101a48800
  R13: ffff88813e3e4150 R14: ffff888130d0d008 R15: ffff88813e3e40d0
  FS:  00007877d3d0d940(0000) GS:ffff88890b6d3000(0000) knlGS:0000000000000000
  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  CR2: 00000000000011f8 CR3: 000000015a762000 CR4: 0000000000f52ef0
  PKRU: 55555554
  Call Trace:
   <TASK>
   xe_vfio_pci_reset_done+0x49/0x120 [xe_vfio_pci]
   pci_dev_restore+0x3b/0x80
   pci_reset_function+0x109/0x140
   reset_store+0x5c/0xb0
   dev_attr_store+0x17/0x40
   sysfs_kf_write+0x72/0x90
   kernfs_fop_write_iter+0x161/0x1f0
   vfs_write+0x261/0x440
   ksys_write+0x69/0xf0
   __x64_sys_write+0x19/0x30
   x64_sys_call+0x259/0x26e0
   do_syscall_64+0xcb/0x1500
   ? __fput+0x1a2/0x2d0
   ? fput_close_sync+0x3d/0xa0
   ? __x64_sys_close+0x3e/0x90
   ? x64_sys_call+0x1b7c/0x26e0
   ? do_syscall_64+0x109/0x1500
   ? __task_pid_nr_ns+0x68/0x100
   ? __do_sys_getpid+0x1d/0x30
   ? x64_sys_call+0x10b5/0x26e0
   ? do_syscall_64+0x109/0x1500
   ? putname+0x41/0x90
   ? do_faccessat+0x1e8/0x300
   ? __x64_sys_access+0x1c/0x30
   ? x64_sys_call+0x1822/0x26e0
   ? do_syscall_64+0x109/0x1500
   ? tick_program_event+0x43/0xa0
   ? hrtimer_interrupt+0x126/0x260
   ? irqentry_exit+0xb2/0x710
   entry_SYSCALL_64_after_hwframe+0x76/0x7e
  RIP: 0033:0x7877d5f1c5a4
  Code: c7 00 16 00 00 00 b8 ff ff ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 f3 0f 1e fa 80 3d a5 ea 0e 00 00 74 13 b8 01 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 54 c3 0f 1f 00 55 48 89 e5 48 83 ec 20 48 89
  RSP: 002b:00007fff48e5f908 EFLAGS: 00000202 ORIG_RAX: 0000000000000001
  RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007877d5f1c5a4
  RDX: 0000000000000001 RSI: 00007877d621b0c9 RDI: 0000000000000009
  RBP: 0000000000000001 R08: 00005fb49113b010 R09: 0000000000000007
  R10: 0000000000000000 R11: 0000000000000202 R12: 00007877d621b0c9
  R13: 0000000000000009 R14: 00007fff48e5fac0 R15: 00007fff48e5fac0
   </TASK>

This is caused by the fact that some of the xe_vfio_pci_core_device
members needed for handling reset are only initialized as part of
migration init.

Fix the problem by reorganizing the code to decouple VF init from
migration init.
CVSS v3.1: 5.5