From: Nicholas Piggin npiggin@gmail.com

[ commit 21a741eb75f80397e5f7d3739e24d7d75e619011 upstream ]

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 [pSeries_machine_kexec hadn't been moved to kexec.c in v5.10, fix context accordingly] Signed-off-by: Feng Liu Feng.Liu3@windriver.com Signed-off-by: He Zhe Zhe.He@windriver.com --- Verified the build test. --- arch/powerpc/kexec/core_64.c | 11 +++++++++++ arch/powerpc/platforms/pseries/setup.c | 11 ----------- 2 files changed, 11 insertions(+), 11 deletions(-)

diff --git a/arch/powerpc/kexec/core_64.c b/arch/powerpc/kexec/core_64.c index 8a449b2d8715..ffc57d5a39a6 100644 --- a/arch/powerpc/kexec/core_64.c +++ b/arch/powerpc/kexec/core_64.c @@ -26,6 +26,7 @@ #include <asm/mmu.h> #include <asm/sections.h> /* _end */ #include <asm/prom.h> +#include <asm/setup.h> #include <asm/smp.h> #include <asm/hw_breakpoint.h> #include <asm/asm-prototypes.h> @@ -313,6 +314,16 @@ 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. diff --git a/arch/powerpc/platforms/pseries/setup.c b/arch/powerpc/platforms/pseries/setup.c index 8e4a2e8aee11..be4d35354daf 100644 --- a/arch/powerpc/platforms/pseries/setup.c +++ b/arch/powerpc/platforms/pseries/setup.c @@ -409,16 +409,6 @@ void pseries_disable_reloc_on_exc(void) } EXPORT_SYMBOL(pseries_disable_reloc_on_exc);

-#ifdef CONFIG_KEXEC_CORE -static void pSeries_machine_kexec(struct kimage *image) -{ - if (firmware_has_feature(FW_FEATURE_SET_MODE)) - pseries_disable_reloc_on_exc(); - - default_machine_kexec(image); -} -#endif - #ifdef __LITTLE_ENDIAN__ void pseries_big_endian_exceptions(void) { @@ -1071,7 +1061,6 @@ define_machine(pseries) { .machine_check_early = pseries_machine_check_realmode, .machine_check_exception = pSeries_machine_check_exception, #ifdef CONFIG_KEXEC_CORE - .machine_kexec = pSeries_machine_kexec, .kexec_cpu_down = pseries_kexec_cpu_down, #endif #ifdef CONFIG_MEMORY_HOTPLUG_SPARSE