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powerpc/pseries: Fix scv instruction crash with kexec

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kexec on pseries disables AIL (reloc_on_exc), required for scv
instruction support, before other CPUs have been shut down. This means
they can execute scv instructions after AIL is disabled, which causes an
interrupt at an unexpected entry location that crashes the kernel.

Change the kexec sequence to disable AIL after other CPUs have been
brought down.

As a refresher, the real-mode scv interrupt vector is 0x17000, and the
fixed-location head code probably couldn't easily deal with implementing
such high addresses so it was just decided not to support that interrupt
at all.

Fixes: 7fa95f9adaee ("powerpc/64s: system call support for scv/rfscv instructions")
Cc: stable@vger.kernel.org # v5.9+
Reported-by: Sourabh Jain <sourabhjain@linux.ibm.com>
Closes: https://lore.kernel.org/3b4b2943-49ad-4619-b195-bc416f1d1409@linux.ibm.com
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Tested-by: Gautam Menghani <gautam@linux.ibm.com>
Tested-by: Sourabh Jain <sourabhjain@linux.ibm.com>
Link: https://msgid.link/20240625134047.298759-1-npiggin@gmail.com
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Nicholas Piggin 2024-06-25 23:40:47 +10:00 committed by Michael Ellerman
parent a1216e62d0
commit 21a741eb75
4 changed files with 11 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

11
arch/powerpc/kexec/core_64.c
View File

@ -27,6 +27,7 @@
#include <asm/paca.h>
#include <asm/mmu.h>
#include <asm/sections.h> /* _end */
#include <asm/setup.h>
#include <asm/smp.h>
#include <asm/hw_breakpoint.h>
#include <asm/svm.h>
@ -317,6 +318,16 @@ void default_machine_kexec(struct kimage *image)
if (!kdump_in_progress())
kexec_prepare_cpus();
#ifdef CONFIG_PPC_PSERIES
/*
* This must be done after other CPUs have shut down, otherwise they
* could execute the 'scv' instruction, which is not supported with
* reloc disabled (see configure_exceptions()).
*/
if (firmware_has_feature(FW_FEATURE_SET_MODE))
pseries_disable_reloc_on_exc();
#endif
printk("kexec: Starting switchover sequence.\n");
/* switch to a staticly allocated stack. Based on irq stack code.

8
arch/powerpc/platforms/pseries/kexec.c
View File

@ -61,11 +61,3 @@ void pseries_kexec_cpu_down(int crash_shutdown, int secondary)
} else
xics_kexec_teardown_cpu(secondary);
}
void pseries_machine_kexec(struct kimage *image)
{
if (firmware_has_feature(FW_FEATURE_SET_MODE))
pseries_disable_reloc_on_exc();
default_machine_kexec(image);
}

1
arch/powerpc/platforms/pseries/pseries.h
View File

@ -38,7 +38,6 @@ static inline void smp_init_pseries(void) { }
#endif
extern void pseries_kexec_cpu_down(int crash_shutdown, int secondary);
void pseries_machine_kexec(struct kimage *image);
extern void pSeries_final_fixup(void);

1
arch/powerpc/platforms/pseries/setup.c
View File

@ -1159,7 +1159,6 @@ define_machine(pseries) {
.machine_check_exception = pSeries_machine_check_exception,
.machine_check_log_err = pSeries_machine_check_log_err,
#ifdef CONFIG_KEXEC_CORE
.machine_kexec = pseries_machine_kexec,
.kexec_cpu_down = pseries_kexec_cpu_down,
#endif
#ifdef CONFIG_MEMORY_HOTPLUG