Message-ID: <20240413024956.488d474e@yea>
Date: Sat, 13 Apr 2024 02:49:56 +0200
From: Erhard Furtner <erhard_f@...lbox.org>
To: x86@...nel.org
Cc: linux-kernel@...r.kernel.org, jpoimboe@...nel.org
Subject: [bisected] Kernel v6.9-rc3 fails to boot on a Thinkpad T60 with
 MITIGATION_RETHUNK=y (regression from v6.8.5)

Greetings!

With MITIGATION_RETHUNK=y selected in kernel .config v6.9-rc3 fails to boot on my Thinkpad T60. The resulting kernel stalls booting at "x86/fpu: x87 FPU will use FXSAVE":

Linux version 6.9.0-rc3-P3 (root@...ah) (gcc (Gentoo 13.2.1_p20240210 p14) 13.2.1 20240210, GNU ld (Gentoo 2.41 p5) 2.41.0) #3 SMP Fri Apr 12 20:09:09 -00 2024
KERNEL supported cpus:
  Intel GenuineIntel
Disabled fast string operations
BIOS-provided physical RAM map:
BIOS-e820: [mem 0x0000000000000000-0x000000000009efff] usable
BIOS-e820: [mem 0x000000000009f000-0x000000000009ffff] reserved
BIOS-e820: [mem 0x00000000000dc000-0x00000000000fffff] reserved
BIOS-e820: [mem 0x0000000000100000-0x00000000bfecffff] usable
BIOS-e820: [mem 0x00000000bfed0000-0x00000000bfedefff] ACPI data
BIOS-e820: [mem 0x00000000bfedf000-0x00000000bfefffff] ACPI NVS
BIOS-e820: [mem 0x00000000bff00000-0x00000000bfffffff] reserved
BIOS-e820: [mem 0x00000000f0000000-0x00000000f3ffffff] reserved
BIOS-e820: [mem 0x00000000fec00000-0x00000000fec0ffff] reserved
BIOS-e820: [mem 0x00000000fed00000-0x00000000fed003ff] reserved
BIOS-e820: [mem 0x00000000fed14000-0x00000000fed19fff] reserved
BIOS-e820: [mem 0x00000000fed1c000-0x00000000fed8ffff] reserved
BIOS-e820: [mem 0x00000000fee00000-0x00000000fee00fff] reserved
BIOS-e820: [mem 0x00000000ff800000-0x00000000ffffffff] reserved
NX (Execute Disable) protection: active
APIC: Static calls initialized
SMBIOS 2.4 present.
DMI: LENOVO 2007F2G/2007F2G, BIOS 79ETE7WW (2.27 ) 03/21/2011
tsc: Fast TSC calibration using PIT
tsc: Detected 1828.722 MHz processor
last_pfn = 0xbfed0 max_arch_pfn = 0x1000000
total RAM covered: 3071M
Found optimal setting for mtrr clean up
 gran_size: 64K 	chunk_size: 2M 	num_reg: 3  	lose cover RAM: 0G
MTRR map: 8 entries (6 fixed + 2 variable; max 22), built from 8 variable MTRRs
x86/PAT: PAT not supported by the CPU.
x86/PAT: Configuration [0-7]: WB  WT  UC- UC  WB  WT  UC- UC  
found SMP MP-table at [mem 0x000f6810-0x000f681f]
ACPI: Early table checksum verification disabled
ACPI: RSDP 0x00000000000F67E0 000024 (v02 LENOVO)
ACPI: XSDT 0x00000000BFED14A0 000084 (v01 LENOVO TP-79    00002270  LTP 00000000)
ACPI: FACP 0x00000000BFED1600 0000F4 (v03 LENOVO TP-79    00002270 LNVO 00000001)
ACPI BIOS Warning (bug): 32/64X length mismatch in FADT/Gpe0Block: 64/32 (20230628/tbfadt-564)
ACPI BIOS Warning (bug): Optional FADT field Gpe1Block has valid Address but zero Length: 0x000000000000102C/0x0 (20230628/tbfadt-615)
ACPI: DSDT 0x00000000BFED195E 00D467 (v01 LENOVO TP-79    00002270 MSFT 0100000E)
ACPI: FACS 0x00000000BFEF4000 000040
ACPI: FACS 0x00000000BFEF4000 000040
ACPI: SSDT 0x00000000BFED17B4 0001AA (v01 LENOVO TP-79    00002270 MSFT 0100000E)
ACPI: ECDT 0x00000000BFEDEDC5 000052 (v01 LENOVO TP-79    00002270 LNVO 00000001)
ACPI: TCPA 0x00000000BFEDEE17 000032 (v02 LENOVO TP-79    00002270 LNVO 00000001)
ACPI: APIC 0x00000000BFEDEE49 000068 (v01 LENOVO TP-79    00002270 LNVO 00000001)
ACPI: MCFG 0x00000000BFEDEEB1 00003C (v01 LENOVO TP-79    00002270 LNVO 00000001)
ACPI: HPET 0x00000000BFEDEEED 000038 (v01 LENOVO TP-79    00002270 LNVO 00000001)
ACPI: BOOT 0x00000000BFEDEFD8 000028 (v01 LENOVO TP-79    00002270  LTP 00000001)
ACPI: SSDT 0x00000000BFEF2655 00025F (v01 LENOVO TP-79    00002270 INTL 20050513)
ACPI: SSDT 0x00000000BFEF28B4 0000A6 (v01 LENOVO TP-79    00002270 INTL 20050513)
ACPI: SSDT 0x00000000BFEF295A 0004F7 (v01 LENOVO TP-79    00002270 INTL 20050513)
ACPI: SSDT 0x00000000BFEF2E51 0001D8 (v01 LENOVO TP-79    00002270 INTL 20050513)
ACPI: Reserving FACP table memory at [mem 0xbfed1600-0xbfed16f3]
ACPI: Reserving DSDT table memory at [mem 0xbfed195e-0xbfededc4]
ACPI: Reserving FACS table memory at [mem 0xbfef4000-0xbfef403f]
ACPI: Reserving FACS table memory at [mem 0xbfef4000-0xbfef403f]
ACPI: Reserving SSDT table memory at [mem 0xbfed17b4-0xbfed195d]
ACPI: Reserving ECDT table memory at [mem 0xbfededc5-0xbfedee16]
ACPI: Reserving TCPA table memory at [mem 0xbfedee17-0xbfedee48]
ACPI: Reserving APIC table memory at [mem 0xbfedee49-0xbfedeeb0]
ACPI: Reserving MCFG table memory at [mem 0xbfedeeb1-0xbfedeeec]
ACPI: Reserving HPET table memory at [mem 0xbfedeeed-0xbfedef24]
ACPI: Reserving BOOT table memory at [mem 0xbfedefd8-0xbfedefff]
ACPI: Reserving SSDT table memory at [mem 0xbfef2655-0xbfef28b3]
ACPI: Reserving SSDT table memory at [mem 0xbfef28b4-0xbfef2959]
ACPI: Reserving SSDT table memory at [mem 0xbfef295a-0xbfef2e50]
ACPI: Reserving SSDT table memory at [mem 0xbfef2e51-0xbfef3028]
2184MB HIGHMEM available.
885MB LOWMEM available.
  mapped low ram: 0 - 375fe000
  low ram: 0 - 375fe000
Zone ranges:
  DMA      [mem 0x0000000000001000-0x0000000000ffffff]
  Normal   [mem 0x0000000001000000-0x00000000375fdfff]
  HighMem  [mem 0x00000000375fe000-0x00000000bfecffff]
Movable zone start for each node
Early memory node ranges
  node   0: [mem 0x0000000000001000-0x000000000009efff]
  node   0: [mem 0x0000000000100000-0x00000000bfecffff]
Initmem setup node 0 [mem 0x0000000000001000-0x00000000bfecffff]
On node 0, zone DMA: 1 pages in unavailable ranges
On node 0, zone DMA: 97 pages in unavailable ranges
ACPI: PM-Timer IO Port: 0x1008
ACPI: LAPIC_NMI (acpi_id[0x00] high edge lint[0x1])
ACPI: LAPIC_NMI (acpi_id[0x01] high edge lint[0x1])
IOAPIC[0]: apic_id 1, version 32, address 0xfec00000, GSI 0-23
ACPI: INT_SRC_OVR (bus 0 bus_irq 0 global_irq 2 dfl dfl)
ACPI: INT_SRC_OVR (bus 0 bus_irq 9 global_irq 9 high level)
ACPI: Using ACPI (MADT) for SMP configuration information
ACPI: HPET id: 0x8086a201 base: 0xfed00000
CPU topo: Max. logical packages:   1
CPU topo: Max. logical dies:       1
CPU topo: Max. dies per package:   1
CPU topo: Max. threads per core:   1
CPU topo: Num. cores per package:     2
CPU topo: Num. threads per package:   2
CPU topo: Allowing 2 present CPUs plus 0 hotplug CPUs
[mem 0xc0000000-0xefffffff] available for PCI devices
clocksource: refined-jiffies: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 6370452778343963 ns
setup_percpu: NR_CPUS:2 nr_cpumask_bits:2 nr_cpu_ids:2 nr_node_ids:1
percpu: Embedded 44 pages/cpu s89216 r0 d91008 u180224
Kernel command line: BOOT_IMAGE=/boot/vmlinuz-6.9.0-rc3-P3 root=PARTUUID=f6cdabc7-801d-4572-9de8-9b696dc216cc ro systemd.gpt_auto=no mce=0 slub_debug=FZP page_poison=1 netconsole=6666@....168.2.10/eth0,6666@....168.2.3/A8:A1:59:16:4F:EA
Unknown kernel command line parameters "BOOT_IMAGE=/boot/vmlinuz-6.9.0-rc3-P3", will be passed to user space.
Dentry cache hash table entries: 131072 (order: 7, 524288 bytes, linear)
Inode-cache hash table entries: 65536 (order: 6, 262144 bytes, linear)
Built 1 zonelists, mobility grouping on.  Total pages: 783815
allocated 3148604 bytes of page_ext
mem auto-init: stack:all(pattern), heap alloc:off, heap free:off
Initializing HighMem for node 0 (000375fe:000bfed0)
Initializing Movable for node 0 (00000000:00000000)
Checking if this processor honours the WP bit even in supervisor mode...Ok.
Memory: 3091260K/3144120K available (9854K kernel code, 555K rwdata, 2532K rodata, 764K init, 320K bss, 52860K reserved, 0K cma-reserved, 2237256K highmem)
**********************************************************
**   NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE   **
**                                                      **
** This system shows unhashed kernel memory addresses   **
** via the console, logs, and other interfaces. This    **
** might reduce the security of your system.            **
**                                                      **
** If you see this message and you are not debugging    **
** the kernel, report this immediately to your system   **
** administrator!                                       **
**                                                      **
**   NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE   **
**********************************************************
SLUB: HWalign=64, Order=0-3, MinObjects=0, CPUs=2, Nodes=1
Kernel/User page tables isolation: enabled
rcu: Hierarchical RCU implementation.
	Tracing variant of Tasks RCU enabled.
rcu: RCU calculated value of scheduler-enlistment delay is 30 jiffies.
RCU Tasks Trace: Setting shift to 1 and lim to 1 rcu_task_cb_adjust=1.
NR_IRQS: 2304, nr_irqs: 440, preallocated irqs: 16
rcu: srcu_init: Setting srcu_struct sizes based on contention.
kfence: initialized - using 2097152 bytes for 255 objects at 0xf51e0000-0xf53e0000
Console: colour VGA+ 80x25
printk: legacy console [tty0] enabled
ACPI: Core revision 20230628
clocksource: hpet: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 133484882848 ns
APIC: Switch to symmetric I/O mode setup
.TIMER: vector=0x30 apic1=0 pin1=2 apic2=-1 pin2=-1
clocksource: tsc-early: mask: 0xffffffffffffffff max_cycles: 0x1a5c261a01f, max_idle_ns: 440795236171 ns
Calibrating delay loop (skipped), value calculated using timer frequency.. 3658.83 BogoMIPS (lpj=6095740)
Disabled fast string operations
CPU0: Thermal monitoring enabled (TM2)
Last level iTLB entries: 4KB 128, 2MB 0, 4MB 2
Last level dTLB entries: 4KB 128, 2MB 0, 4MB 8, 1GB 0
process: using mwait in idle threads
Spectre V1 : Mitigation: usercopy/swapgs barriers and __user pointer sanitization
Spectre V2 : Mitigation: Retpolines
Spectre V2 : Spectre v2 / SpectreRSB mitigation: Filling RSB on context switch
Spectre V2 : Spectre v2 / SpectreRSB : Filling RSB on VMEXIT
L1TF: System has more than MAX_PA/2 memory. L1TF mitigation not effective.
L1TF: You may make it effective by booting the kernel with mem=2147483648 parameter.
L1TF: However, doing so will make a part of your RAM unusable.
L1TF: Reading https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/l1tf.html might help you decide.
MDS: Vulnerable: Clear CPU buffers attempted, no microcode
MMIO Stale Data: Unknown: No mitigations
x86/fpu: x87 FPU will use FXSAVE

Without MITIGATION_RETHUNK selected v6.9-rc3 boots fine. Also v6.8.5 with MITIGATION_RETHUNK=y selected boots fine. So I bisected the issue and got this result:

 # git bisect good
4461438a8405e800f90e0e40409e5f3d07eed381 is the first bad commit
commit 4461438a8405e800f90e0e40409e5f3d07eed381
Author: Josh Poimboeuf <jpoimboe@...nel.org>
Date:   Wed Jan 3 19:36:26 2024 +0100

    x86/retpoline: Ensure default return thunk isn't used at runtime
    
    Make sure the default return thunk is not used after all return
    instructions have been patched by the alternatives because the default
    return thunk is insufficient when it comes to mitigating Retbleed or
    SRSO.
    
    Fix based on an earlier version by David Kaplan <david.kaplan@....com>.
    
      [ bp: Fix the compilation error of warn_thunk_thunk being an invisible
            symbol, hoist thunk macro into calling.h ]
    
    Signed-off-by: Josh Poimboeuf <jpoimboe@...nel.org>
    Co-developed-by: Borislav Petkov (AMD) <bp@...en8.de>
    Signed-off-by: Borislav Petkov (AMD) <bp@...en8.de>
    Link: https://lore.kernel.org/r/20231010171020.462211-4-david.kaplan@amd.com
    Link: https://lore.kernel.org/r/20240104132446.GEZZaxnrIgIyat0pqf@fat_crate.local

 arch/x86/entry/calling.h             | 60 ++++++++++++++++++++++++++++++++++++
 arch/x86/entry/entry.S               |  4 +++
 arch/x86/entry/thunk_32.S            | 34 +++++---------------
 arch/x86/entry/thunk_64.S            | 33 --------------------
 arch/x86/include/asm/nospec-branch.h |  2 ++
 arch/x86/kernel/cpu/bugs.c           |  5 +++
 arch/x86/lib/retpoline.S             | 15 ++++-----
 7 files changed, 85 insertions(+), 68 deletions(-)


Indeed when reverting 4461438a8405e800f90e0e40409e5f3d07eed381 v6.9-rc3 boots
fine again. Reverting the commit was not straight forward however, I had to
remove "THUNK warn_thunk_thunk, __warn_thunk" from v6-9-rc3s
arch/x86/entry/entry.S to make the kernel build. Otherwise it would complain
about "Error: no such instruction: `thunk warn_thunk_thunk,__warn_thunk'"

Some data about the machine:

 # inxi -bz
System:
  Kernel: 6.9.0-rc3-P3 arch: i686 bits: 32 Console: pty pts/0 Distro: Gentoo
    Base System release 2.14
Machine:
  Type: Laptop System: LENOVO product: 2007F2G v: ThinkPad T60
    serial: <filter>
  Mobo: LENOVO model: 2007F2G serial: <filter> BIOS: LENOVO
    v: 79ETE7WW (2.27 ) date: 03/21/2011
Battery:
  ID-1: BAT0 charge: 0 Wh (0.0%) condition: 35.7/56.2 Wh (63.6%) volts: 7.4
    min: 10.8
CPU:
  Info: dual core Intel T2400 [MCP] speed (MHz): avg: 1000 min/max: 1000/1833
Graphics:
  Device-1: AMD RV515/M52 [Mobility Radeon X1300] driver: radeon v: kernel
  Display: x11 server: X.org v: 1.21.1.11 driver: X: loaded: radeon
    unloaded: fbdev,modesetting dri: r300 gpu: radeon
    resolution: <missing: xdpyinfo/xrandr> resolution: 1024x768
  API: OpenGL v: 4.5 vendor: mesa v: 24.0.4 renderer: llvmpipe (LLVM 17.0.6
    128 bits)
Network:
  Device-1: Intel 82573L Gigabit Ethernet driver: e1000e
  Device-2: Intel PRO/Wireless 3945ABG [Golan] Network driver: iwl3945
Drives:
  Local Storage: total: 465.76 GiB used: 10.26 GiB (2.2%)
Info:
  Processes: 159 Uptime: 1m Memory: total: 3 GiB available: 2.95 GiB
  used: 477.2 MiB (15.8%) igpu: 128 KiB Shell: Bash inxi: 3.3.30

 # lscpu 
Architecture:             i686
  CPU op-mode(s):         32-bit
  Address sizes:          32 bits physical, 32 bits virtual
  Byte Order:             Little Endian
CPU(s):                   2
  On-line CPU(s) list:    0,1
Vendor ID:                GenuineIntel
  BIOS Vendor ID:         GenuineIntel
  Model name:             Genuine Intel(R) CPU           T2400  @ 1.83GHz
    BIOS Model name:      Genuine Intel(R) CPU             CPU @ 1.8GHz
    BIOS CPU family:      1
    CPU family:           6
    Model:                14
    Thread(s) per core:   1
    Core(s) per socket:   2
    Socket(s):            1
    Stepping:             8
    CPU(s) scaling MHz:   54%
    CPU max MHz:          1833,0000
    CPU min MHz:          1000,0000
    BogoMIPS:             3658,83
    Flags:                fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov clflush 
                          dts acpi mmx fxsr sse sse2 ht tm pbe nx constant_tsc arch_perfmon bts 
                          cpuid aperfmperf pni monitor vmx est tm2 xtpr pdcm pti dtherm
Virtualization features:  
  Virtualization:         VT-x
Caches (sum of all):      
  L1d:                    64 KiB (2 instances)
  L1i:                    64 KiB (2 instances)
  L2:                     2 MiB (1 instance)


Attached please find the kernel .config and the bisect.log.

Regards,
Erhard

Download attachment "config_69-rc3_p3" of type "application/octet-stream" (137374 bytes)

View attachment "bisect.log" of type "text/x-log" (2980 bytes)

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