[PATCH 5.10.y] powerpc/pseries: Fix scv instruction crash with kexec

[PATCH 5.10.y] powerpc/pseries: Fix scv instruction crash with kexec

[Feng Liu]

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
-- 
2.34.1

[PATCH 5.15.y] powerpc/pseries: Fix scv instruction crash with kexec

[Feng Liu]

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>
[Minor context change fixed]
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 89c069d664a5..09d59628a499 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>
@@ -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.
diff --git a/arch/powerpc/platforms/pseries/setup.c b/arch/powerpc/platforms/pseries/setup.c
index 309a72518ecc..95c9d1e38f4b 100644
--- a/arch/powerpc/platforms/pseries/setup.c
+++ b/arch/powerpc/platforms/pseries/setup.c
@@ -411,16 +411,6 @@ 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)
 {
@@ -1088,7 +1078,6 @@ 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
-- 
2.34.1

Re: [PATCH 5.15.y] powerpc/pseries: Fix scv instruction crash with kexec

[Sasha Levin]

[ Sasha's backport helper bot ]

Hi,

✅ All tests passed successfully. No issues detected.
No action required from the submitter.

The upstream commit SHA1 provided is correct: 21a741eb75f80397e5f7d3739e24d7d75e619011

WARNING: Author mismatch between patch and upstream commit:
Backport author: Feng Liu<Feng.Liu3@windriver.com>
Commit author: Nicholas Piggin<npiggin@gmail.com>

Status in newer kernel trees:
6.14.y | Present (exact SHA1)
6.12.y | Present (exact SHA1)
6.6.y | Present (different SHA1: d10e3c39001e)
6.1.y | Present (different SHA1: c550679d6047)

Note: The patch differs from the upstream commit:
---
1:  21a741eb75f80 < -:  ------------- powerpc/pseries: Fix scv instruction crash with kexec
-:  ------------- > 1:  c013f06b90b03 powerpc/pseries: Fix scv instruction crash with kexec
---

Results of testing on various branches:

| Branch                    | Patch Apply | Build Test |
|---------------------------|-------------|------------|
| stable/linux-5.15.y       |  Success    |  Success   |

Re: [PATCH 5.10.y] powerpc/pseries: Fix scv instruction crash with kexec

[Sasha Levin]

[ Sasha's backport helper bot ]

Hi,

✅ All tests passed successfully. No issues detected.
No action required from the submitter.

The upstream commit SHA1 provided is correct: 21a741eb75f80397e5f7d3739e24d7d75e619011

WARNING: Author mismatch between patch and upstream commit:
Backport author: Feng Liu<Feng.Liu3@windriver.com>
Commit author: Nicholas Piggin<npiggin@gmail.com>

Status in newer kernel trees:
6.14.y | Present (exact SHA1)
6.12.y | Present (exact SHA1)
6.6.y | Present (different SHA1: d10e3c39001e)
6.1.y | Present (different SHA1: c550679d6047)
5.15.y | Not found

Note: The patch differs from the upstream commit:
---
1:  21a741eb75f80 < -:  ------------- powerpc/pseries: Fix scv instruction crash with kexec
-:  ------------- > 1:  12501a36cead8 powerpc/pseries: Fix scv instruction crash with kexec
---

Results of testing on various branches:

| Branch                    | Patch Apply | Build Test |
|---------------------------|-------------|------------|
| stable/linux-5.10.y       |  Success    |  Success   |