kernel.git/arch/powerpc/kernel/setup_64.c, branch linux-6.1.y

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

2024-12-14T18:53:58Z

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: Avoid nmi_enter/nmi_exit in real mode interrupt.

2024-07-11T10:47:05Z

[ Upstream commit 0db880fc865ffb522141ced4bfa66c12ab1fbb70 ] 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 Signed-off-by: Sasha Levin

powerpc/64: Move paca allocation to early_setup()

2023-03-17T07:50:31Z

[ Upstream commit dc222fa7737212fe0da513e5b8937c156d02225d ] 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 Signed-off-by: Sasha Levin

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

2023-03-17T07:50:31Z

[ Upstream commit 9fa24404f5044967753a6cd3e5e36f57686bec6e ] 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 Signed-off-by: Sasha Levin

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

2022-09-28T09:22:13Z

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

2022-09-28T09:22:13Z

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

2022-09-28T09:22:13Z

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

powerpc/64: mark irqs hard disabled in boot paca

2022-09-28T09:22:11Z

This prevents interrupts in early boot (e.g., program check) from enabling MSR[EE], potentially causing endian mismatch or other crashes when reporting early boot traps. Fixes: 4423eb5ae32ec ("powerpc/64/interrupt: make normal synchronous interrupts enable MSR[EE] if possible") Signed-off-by: Nicholas Piggin Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20220926054305.2671436-3-npiggin@gmail.com

powerpc: Remove CONFIG_PPC_BOOK3E

2022-09-26T13:00:13Z

CONFIG_PPC_BOOK3E is redundant with CONFIG_PPC_BOOK3E_64. The later is more explicit about the fact that it's a 64 bits target. Remove CONFIG_PPC_BOOK3E. Signed-off-by: Christophe Leroy Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/5d0891490813c19cdcfc04678f512ea68cba3e64.1663606876.git.christophe.leroy@csgroup.eu

powerpc/64e: Remove MMU_FTR_USE_TLBRSRV and MMU_FTR_USE_PAIRED_MAS

2022-06-29T07:04:14Z

Commit fb5a515704d7 ("powerpc: Remove platforms/wsp and associated pieces") removed the last CPU having features MMU_FTRS_A2 and commit cd68098bcedd ("powerpc: Clean up MMU_FTRS_A2 and MMU_FTR_TYPE_3E") removed MMU_FTRS_A2 which was the last user of MMU_FTR_USE_TLBRSRV and MMU_FTR_USE_PAIRED_MAS. Remove all code that relies on MMU_FTR_USE_TLBRSRV and MMU_FTR_USE_PAIRED_MAS. With this change done, TLB miss can happen before the mmu feature fixups. Signed-off-by: Christophe Leroy Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/cfd5a0ecdb1598da968832e1bddf7431ec267200.1656427701.git.christophe.leroy@csgroup.eu