linux.git/arch/powerpc/kernel/setup_64.c, branch v6.12.80

powerpc/pseries: Fix KVM guest detection for disabling hardlockup detector

2024-12-05T13:02:43+00:00

commit 44e5d21e6d3fd2a1fed7f0327cf72e99397e2eaf upstream.

As per the kernel documentation[1], hardlockup detector should
be disabled in KVM guests as it may give false positives. On
PPC, hardlockup detector is enabled inside KVM guests because
disable_hardlockup_detector() is marked as early_initcall and it
relies on kvm_guest static key (is_kvm_guest()) which is initialized
later during boot by check_kvm_guest(), which is a core_initcall.
check_kvm_guest() is also called in pSeries_smp_probe(), which is called
before initcalls, but it is skipped if KVM guest does not have doorbell
support or if the guest is launched with SMT=1.

Call check_kvm_guest() in disable_hardlockup_detector() so that
is_kvm_guest() check goes through fine and hardlockup detector can be
disabled inside the KVM guest.

[1]: Documentation/admin-guide/sysctl/kernel.rst

Fixes: 633c8e9800f3 ("powerpc/pseries: Enable hardlockup watchdog for PowerVM partitions")
Cc: stable@vger.kernel.org # v5.14+
Signed-off-by: Gautam Menghani 
Signed-off-by: Michael Ellerman 
Link: https://patch.msgid.link/20241108094839.33084-1-gautam@linux.ibm.com
Signed-off-by: Greg Kroah-Hartman

powerpc/64e: drop MMU_FTR_TYPE_FSL_E checks in 64-bit code

2024-07-12T22:52:14+00:00

All 64-bit Book3E have MMU_FTR_TYPE_FSL_E, since A2 was removed, so remove
checks for it in 64-bit only code.

Link: https://lkml.kernel.org/r/2b0b0bc9752e6cece222e4e2050358da70bb631d.1719928057.git.christophe.leroy@csgroup.eu
Signed-off-by: Michael Ellerman 
Signed-off-by: Christophe Leroy 
Cc: Jason Gunthorpe 
Cc: Nicholas Piggin 
Cc: Oscar Salvador 
Cc: Peter Xu 
Signed-off-by: Andrew Morton

powerpc: Avoid nmi_enter/nmi_exit in real mode interrupt.

2024-04-15T02:55:48+00:00

nmi_enter()/nmi_exit() touches per cpu variables which can lead to kernel
crash when invoked during real mode interrupt handling (e.g. early HMI/MCE
interrupt handler) if percpu allocation comes from vmalloc area.

Early HMI/MCE handlers are called through DEFINE_INTERRUPT_HANDLER_NMI()
wrapper which invokes nmi_enter/nmi_exit calls. We don't see any issue when
percpu allocation is from the embedded first chunk. However with
CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK enabled there are chances where percpu
allocation can come from the vmalloc area.

With kernel command line "percpu_alloc=page" we can force percpu allocation
to come from vmalloc area and can see kernel crash in machine_check_early:

[    1.215714] NIP [c000000000e49eb4] rcu_nmi_enter+0x24/0x110
[    1.215717] LR [c0000000000461a0] machine_check_early+0xf0/0x2c0
[    1.215719] --- interrupt: 200
[    1.215720] [c000000fffd73180] [0000000000000000] 0x0 (unreliable)
[    1.215722] [c000000fffd731b0] [0000000000000000] 0x0
[    1.215724] [c000000fffd73210] [c000000000008364] machine_check_early_common+0x134/0x1f8

Fix this by avoiding use of nmi_enter()/nmi_exit() in real mode if percpu
first chunk is not embedded.

Reviewed-by: Christophe Leroy 
Tested-by: Shirisha Ganta 
Signed-off-by: Mahesh Salgaonkar 
Signed-off-by: Michael Ellerman 
Link: https://msgid.link/20240410043006.81577-1-mahesh@linux.ibm.com

powerpc: Use NULL instead of 0 for null pointers

2023-10-19T06:12:47+00:00

Sparse reports several uses of 0 for pointer arguments and comparisons.
Replace with NULL to better convey the intent. Remove entirely if a
comparison to follow the kernel style of implicit boolean conversions.

Signed-off-by: Benjamin Gray 
Signed-off-by: Michael Ellerman 
Link: https://msgid.link/20231011053711.93427-5-bgray@linux.ibm.com

cpu: Mark panic_smp_self_stop() __noreturn

2023-04-14T15:31:25+00:00

In preparation for improving objtool's handling of weak noreturn
functions, mark panic_smp_self_stop() __noreturn.

Signed-off-by: Josh Poimboeuf 
Signed-off-by: Peter Zijlstra (Intel) 
Link: https://lore.kernel.org/r/92d76ab5c8bf660f04fdcd3da1084519212de248.1681342859.git.jpoimboe@kernel.org

powerpc/64: Move paca allocation to early_setup()

2023-02-10T11:19:56+00:00

The early paca and boot cpuid dance is complicated and currently does
not quite work as expected for boot cpuid != 0 cases.

early_init_devtree() currently allocates the paca_ptrs and boot cpuid
paca, but until that returns and early_setup() calls setup_paca(), this
thread is currently still executing with smp_processor_id() == 0.

One problem this causes is the paca_ptrs[smp_processor_id()] pointer is
poisoned, so valid_emergency_stack() (any backtrace) and any similar
users will crash.

Another is that the hardware id which is set here will not be returned
by get_hard_smp_processor_id(smp_processor_id()), but it would work
correctly for boot_cpuid == 0, which could lead to difficult to
reproduce or find bugs. The hard id does not seem to be used by the rest
of early_init_devtree(), it just looks like all this code might have
been put here to allocate somewhere to store boot CPU hardware id while
scanning the devtree.

Rearrange things so the hwid is put in a global variable like
boot_cpuid, and do all the paca allocation and boot paca setup in the
64-bit early_setup() after we have everything ready to go.

The paca_ptrs[0] re-poisoning code in early_setup does not seem to have
ever worked, because paca_ptrs[0] was never not-poisoned when boot_cpuid
is not 0.

Signed-off-by: Nicholas Piggin 
[mpe: Fix build error on 32-bit]
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/20221216115930.2667772-4-npiggin@gmail.com

powerpc/64: Fix task_cpu in early boot when booting non-zero cpuid

2023-02-10T11:19:38+00:00

powerpc/64 can boot on a non-zero SMP processor id. Initially, the boot
CPU is said to be "assumed to be 0" until early_init_devtree() discovers
the id from the device tree. That is not a good description because the
assumption can be wrong and that has to be handled, the better
description is that 0 is used as a placeholder, and things are fixed
after the real id is discovered.

smp_processor_id() is set to the boot cpuid, but task_cpu(current) is
not, which causes the smp_processor_id() == task_cpu(current) invariant
to be broken until init_idle() in sched_init().

This is quite fragile and could lead to subtle bugs in future. One bug
is that validate_sp_size uses task_cpu() to get the process stack, so
any stack trace from the booting CPU between early_init_devtree()
and sched_init() will have problems. Early on paca_ptrs[0] will be
poisoned, so that can cause machine checks dereferencing that memory
in real mode. Later, validating the current stack pointer against the
idle task of a different secondary will probably cause no stack trace
to be printed.

Fix this by setting thread_info->cpu right after smp_processor_id() is
set to the boot cpuid.

Signed-off-by: Nicholas Piggin 
[mpe: Fix SMP=n build as reported by sfr]
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/20221216115930.2667772-3-npiggin@gmail.com

powerpc/64s/interrupt: halt early boot interrupts if paca is not set up

2022-09-28T09:22:13+00:00

Ensure r13 is zero from very early in boot until it gets set to the
boot paca pointer. This allows early program and mce handlers to halt
if there is no valid paca, rather than potentially run off into the
weeds. This preserves register and memory contents for low level
debugging tools.

Nothing could be printed to console at this point in any case because
even udbg is only set up after the boot paca is set, so this shouldn't
be missed.

Signed-off-by: Nicholas Piggin 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/20220926055620.2676869-6-npiggin@gmail.com

powerpc/64: don't set boot CPU's r13 to paca until the structure is set up

2022-09-28T09:22:13+00:00

The idea is to get to the point where if r13 is non-zero, then it should
contain a reasonable paca. This can be used in early boot program check
and machine check handlers to avoid running off into the weeds if they
hit before r13 has a paca.

Signed-off-by: Nicholas Piggin 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/20220926055620.2676869-5-npiggin@gmail.com

powerpc/64s: early boot machine check handler

2022-09-28T09:22:13+00:00

Use the early boot interrupt fixup in the machine check handler to allow
the machine check handler to run before interrupt endian is set up.
Branch to an early boot handler that just does a basic crash, which
allows it to run before ppc_md is set up. MSR[ME] is enabled on the boot
CPU earlier, and the machine check stack is temporarily set to the
middle of the init task stack.

This allows machine checks (e.g., due to invalid data access in real
mode) to print something useful earlier in boot (as soon as udbg is set
up, if CONFIG_PPC_EARLY_DEBUG=y).

Signed-off-by: Nicholas Piggin 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/20220926055620.2676869-3-npiggin@gmail.com