[PATCH 0/2] x86/mpparse, kexec: Fix kdump/kexec kernel panic with MPTABLE and x2apic

[Kairui Song]

From: Kairui Song <kasong@xxxxxxxxxxx>

Following kernel panic is observed when doing kdump/kexec on
qemu-kvm VMs that uses MPTABLE, not ACPI MADT, and supports x2apic:

  Intel MultiProcessor Specification v1.4
  MPTABLE: OEM ID: BOCHSCPU
  MPTABLE: Product ID: 0.1
  MPTABLE: APIC at: 0xFEE00000
  BUG: unable to handle page fault for address: ffffffffff5fc020
  #PF: supervisor read access in kernel mode
  #PF: error_code(0x0000) - not-present page
  PGD 25e15067 P4D 25e15067 PUD 25e17067 PMD 25e18067 PTE 0
  Oops: 0000 [#1] SMP NOPTI
  CPU: 0 PID: 0 Comm: swapper Not tainted 5.14.10-300.fc35.x86_64 #1
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1.fc35 04/01/2014
  RIP: 0010:native_apic_mem_read+0x2/0x10
  Code: 14 25 20 cd e3 82 c3 90 bf 30 08 00 00 ff 14 25 18 cd e3 82 c3 cc cc cc 89 ff 89 b7 00 c0 5f ff c3 0f 1f 80 00 00 00 00 89 ff <8b> 87 00 c0 5f ff c3 0f 1f 80 00 00 00 0
  RSP: 0000:ffffffff82e03e18 EFLAGS: 00010046
  RAX: ffffffff81064840 RBX: ffffffffff240b6c RCX: ffffffff82f17428
  RDX: c0000000ffffdfff RSI: 00000000ffffdfff RDI: 0000000000000020
  RBP: ffff888023200000 R08: 0000000000000000 R09: ffffffff82e03c50
  R10: ffffffff82e03c48 R11: ffffffff82f47468 R12: ffffffffff240b40
  R13: ffffffffff200b30 R14: 0000000000000000 R15: 00000000000000d4
  FS:  0000000000000000(0000) GS:ffffffff8365b000(0000) knlGS:0000000000000000
  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  CR2: ffffffffff5fc020 CR3: 0000000025e10000 CR4: 00000000000006b0
  Call Trace:
   ? read_apic_id+0x15/0x30
   ? register_lapic_address+0x76/0x97
   ? default_get_smp_config+0x28b/0x42d
   ? dmi_check_system+0x1c/0x60
   ? acpi_boot_init+0x1d/0x4c3
   ? setup_arch+0xb37/0xc2a
   ? slab_is_available+0x5/0x10
   ? start_kernel+0x61/0x980
   ? load_ucode_bsp+0x4c/0xcd
   ? secondary_startup_64_no_verify+0xc2/0xcb
  Modules linked in:
  CR2: ffffffffff5fc020
  random: get_random_bytes called from oops_exit+0x35/0x60 with crng_init=0
  ---[ end trace c9e569df3bdbefd3 ]---

It turns out MPTABLE doesn't play well with pre-enabled x2apic mode,
this series extend the apic driver interface and let MPTABLE parse
probe the driver properly.

This can be easily reproduced with qemu-kvm, use -no-acpi and enable
x2apic, so x2apic with MPTABLE will be in use, then trigger kdump/kexec.

Kairui Song (2):
  x86, apic: add a more generic early_probe
  x86/mpparse, kexec: probe apic driver early for x2apic

 arch/x86/include/asm/apic.h           |  6 ++++++
 arch/x86/kernel/apic/probe_64.c       | 16 ++++++++++++++++
 arch/x86/kernel/apic/x2apic_cluster.c |  8 +++++++-
 arch/x86/kernel/apic/x2apic_phys.c    |  8 +++++++-
 arch/x86/kernel/mpparse.c             |  4 +++-
 5 files changed, 39 insertions(+), 3 deletions(-)

-- 
2.35.2