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powerpc: Avoid nmi_enter/nmi_exit in real mode interrupt.

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commit 0db880fc865ffb522141ced4bfa66c12ab1fbb70 upstream.

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 <christophe.leroy@csgroup.eu>
Tested-by: Shirisha Ganta <shirisha@linux.ibm.com>
Signed-off-by: Mahesh Salgaonkar <mahesh@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20240410043006.81577-1-mahesh@linux.ibm.com
[ Conflicts in arch/powerpc/include/asm/interrupt.h
  because machine_check_early() and machine_check_exception()
  has been refactored. ]
Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Mahesh Salgaonkar 2024-04-10 10:00:06 +05:30 committed by Ksawlii
parent de36ead3f3
commit f53d6656c2
4 changed files with 30 additions and 4 deletions
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10
arch/powerpc/include/asm/percpu.h
View file

@ -15,6 +15,16 @@
#endif /* CONFIG_SMP */
#endif /* __powerpc64__ */
#if defined(CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK) && defined(CONFIG_SMP)
#include <linux/jump_label.h>
DECLARE_STATIC_KEY_FALSE(__percpu_first_chunk_is_paged);
#define percpu_first_chunk_is_paged \
(static_key_enabled(&__percpu_first_chunk_is_paged.key))
#else
#define percpu_first_chunk_is_paged false
#endif /* CONFIG_PPC64 && CONFIG_SMP */
#include <asm-generic/percpu.h>
#include <asm/paca.h>

14
arch/powerpc/kernel/mce.c
View file

@ -594,8 +594,15 @@ long notrace machine_check_early(struct pt_regs *regs)
u8 ftrace_enabled = this_cpu_get_ftrace_enabled();
this_cpu_set_ftrace_enabled(0);
/* Do not use nmi_enter/exit for pseries hpte guest */
if (radix_enabled() || !firmware_has_feature(FW_FEATURE_LPAR))
/*
* Do not use nmi_enter/exit for pseries hpte guest
*
* Likewise, do not use it in real mode if percpu first chunk is not
* embedded. With CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK enabled there
* are chances where percpu allocation can come from vmalloc area.
*/
if ((radix_enabled() || !firmware_has_feature(FW_FEATURE_LPAR)) &&
!percpu_first_chunk_is_paged)
nmi_enter();
hv_nmi_check_nonrecoverable(regs);
@ -606,7 +613,8 @@ long notrace machine_check_early(struct pt_regs *regs)
if (ppc_md.machine_check_early)
handled = ppc_md.machine_check_early(regs);
if (radix_enabled() || !firmware_has_feature(FW_FEATURE_LPAR))
if ((radix_enabled() || !firmware_has_feature(FW_FEATURE_LPAR)) &&
!percpu_first_chunk_is_paged)
nmi_exit();
this_cpu_set_ftrace_enabled(ftrace_enabled);

2
arch/powerpc/kernel/setup_64.c
View file

@ -824,6 +824,7 @@ static int pcpu_cpu_distance(unsigned int from, unsigned int to)
unsigned long __per_cpu_offset[NR_CPUS] __read_mostly;
EXPORT_SYMBOL(__per_cpu_offset);
DEFINE_STATIC_KEY_FALSE(__percpu_first_chunk_is_paged);
static void __init pcpu_populate_pte(unsigned long addr)
{
@ -903,6 +904,7 @@ void __init setup_per_cpu_areas(void)
if (rc < 0)
panic("cannot initialize percpu area (err=%d)", rc);
static_key_enable(&__percpu_first_chunk_is_paged.key);
delta = (unsigned long)pcpu_base_addr - (unsigned long)__per_cpu_start;
for_each_possible_cpu(cpu) {
__per_cpu_offset[cpu] = delta + pcpu_unit_offsets[cpu];

8
arch/powerpc/kernel/traps.c
View file

@ -835,8 +835,14 @@ void machine_check_exception(struct pt_regs *regs)
* This is silly. The BOOK3S_64 should just call a different function
* rather than expecting semantics to magically change. Something
* like 'non_nmi_machine_check_exception()', perhaps?
*
* Do not use nmi_enter/exit in real mode if percpu first chunk is
* not embedded. With CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK enabled
* there are chances where percpu allocation can come from
* vmalloc area.
*/
const bool nmi = !IS_ENABLED(CONFIG_PPC_BOOK3S_64);
const bool nmi = !IS_ENABLED(CONFIG_PPC_BOOK3S_64) &&
!percpu_first_chunk_is_paged;
if (nmi) nmi_enter();