Commit 21a741eb authored by Nicholas Piggin's avatar Nicholas Piggin Committed by Michael Ellerman
Browse files

powerpc/pseries: Fix scv instruction crash with kexec 



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: 7fa95f9a ("powerpc/64s: system call support for scv/rfscv instructions")
Cc: stable@vger.kernel.org # v5.9+
Reported-by: default avatarSourabh Jain <sourabhjain@linux.ibm.com>
Closes: https://lore.kernel.org/3b4b2943-49ad-4619-b195-bc416f1d1409@linux.ibm.com


Signed-off-by: default avatarNicholas Piggin <npiggin@gmail.com>
Tested-by: default avatarGautam Menghani <gautam@linux.ibm.com>
Tested-by: default avatarSourabh Jain <sourabhjain@linux.ibm.com>
Link: https://msgid.link/20240625134047.298759-1-npiggin@gmail.com


Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
parent a1216e62

arch/powerpc/kexec/core_64.c

+11 −0
Original line number Diff line number Diff line
@@ -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.

arch/powerpc/platforms/pseries/kexec.c

+0 −8
Original line number Diff line number Diff line
@@ -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);

}

arch/powerpc/platforms/pseries/pseries.h

+0 −1
Original line number Diff line number Diff line
@@ -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);

arch/powerpc/platforms/pseries/setup.c

+0 −1
Original line number Diff line number Diff line
@@ -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