[PATCH v9 0/7] powerpc: implement machine check safe memcpy

[PATCH v9 0/7] powerpc: implement machine check safe memcpy

[Santosh Sivaraj]

During a memcpy from a pmem device, if a machine check exception is
generated we end up in a panic. In case of fsdax read, this should
only result in a -EIO. Avoid MCE by implementing memcpy_mcsafe.

Before this patch series:

```
bash-4.4# mount -o dax /dev/pmem0 /mnt/pmem/
[ 7621.714094] Disabling lock debugging due to kernel taint
[ 7621.714099] MCE: CPU0: machine check (Severe) Host UE Load/Store [Not recovered]
[ 7621.714104] MCE: CPU0: NIP: [c000000000088978] memcpy_power7+0x418/0x7e0
[ 7621.714107] MCE: CPU0: Hardware error
[ 7621.714112] opal: Hardware platform error: Unrecoverable Machine Check exception
[ 7621.714118] CPU: 0 PID: 1368 Comm: mount Tainted: G   M              5.2.0-rc5-00239-g241e39004581
#50
[ 7621.714123] NIP:  c000000000088978 LR: c0000000008e16f8 CTR: 00000000000001de
[ 7621.714129] REGS: c0000000fffbfd70 TRAP: 0200   Tainted: G   M              
(5.2.0-rc5-00239-g241e39004581)
[ 7621.714131] MSR:  9000000002209033 <SF,HV,VEC,EE,ME,IR,DR,RI,LE>  CR: 24428840  XER: 00040000
[ 7621.714160] CFAR: c0000000000889a8 DAR: deadbeefdeadbeef DSISR: 00008000 IRQMASK: 0
[ 7621.714171] GPR00: 000000000e000000 c0000000f0b8b1e0 c0000000012cf100 c0000000ed8e1100 
[ 7621.714186] GPR04: c000020000001100 0000000000010000 0000000000000200 03fffffff1272000 
[ 7621.714201] GPR08: 0000000080000000 0000000000000010 0000000000000020 0000000000000030 
[ 7621.714216] GPR12: 0000000000000040 00007fffb8c6d390 0000000000000050 0000000000000060 
[ 7621.714232] GPR16: 0000000000000070 0000000000000000 0000000000000001 c0000000f0b8b960 
[ 7621.714247] GPR20: 0000000000000001 c0000000f0b8b940 0000000000000001 0000000000010000 
[ 7621.714262] GPR24: c000000001382560 c00c0000003b6380 c00c0000003b6380 0000000000010000 
[ 7621.714277] GPR28: 0000000000000000 0000000000010000 c000020000000000 0000000000010000 
[ 7621.714294] NIP [c000000000088978] memcpy_power7+0x418/0x7e0
[ 7621.714298] LR [c0000000008e16f8] pmem_do_bvec+0xf8/0x430
... <snip> ...
```

After this patch series:

```
bash-4.4# mount -o dax /dev/pmem0 /mnt/pmem/
[25302.883978] Buffer I/O error on dev pmem0, logical block 0, async page read
[25303.020816] EXT4-fs (pmem0): DAX enabled. Warning: EXPERIMENTAL, use at your own risk
[25303.021236] EXT4-fs (pmem0): Can't read superblock on 2nd try
[25303.152515] EXT4-fs (pmem0): DAX enabled. Warning: EXPERIMENTAL, use at your own risk
[25303.284031] EXT4-fs (pmem0): DAX enabled. Warning: EXPERIMENTAL, use at your own risk
[25304.084100] UDF-fs: bad mount option "dax" or missing value
mount: /mnt/pmem: wrong fs type, bad option, bad superblock on /dev/pmem0, missing codepage or helper
program, or other error.
```

MCE is injected on a pmem address using mambo. The last patch which adds a
nop is only for testing on mambo, where r13 is not restored upon hitting
vector 200.

The memcpy code can be optimised by adding VMX optimizations and GAS macros
can be used to enable code reusablity, which I will send as another series.

---
Change-log:
v9:
* Add a new IRQ work for UE events [mahesh]
* Reorder patches, and copy stable

v8:
* While ignoring UE events, return was used instead of continue.
* Checkpatch fixups for commit log

v7:
* Move schedule_work to be called from irq_work.

v6:
* Don't return pfn, all callees are expecting physical address anyway [nick]
* Patch re-ordering: move exception table patch before memcpy_mcsafe patch [nick]
* Reword commit log for search_exception_tables patch [nick]

v5:
* Don't use search_exception_tables since it searches for module exception tables
  also [Nicholas]
* Fix commit message for patch 2 [Nicholas]

v4:
* Squash return remaining bytes patch to memcpy_mcsafe implemtation patch [christophe]
* Access ok should be checked for copy_to_user_mcsafe() [christophe]

v3:
* Drop patch which enables DR/IR for external modules
* Drop notifier call chain, we don't want to do that in real mode
* Return remaining bytes from memcpy_mcsafe correctly
* We no longer restore r13 for simulator tests, rather use a nop at 
  vector 0x200 [workaround for simulator; not to be merged]

v2:
* Don't set RI bit explicitly [mahesh]
* Re-ordered series to get r13 workaround as the last patch
--
Balbir Singh (2):
  powerpc/mce: Fix MCE handling for huge pages
  powerpc/memcpy: Add memcpy_mcsafe for pmem

Reza Arbab (1):
  powerpc/mce: Make machine_check_ue_event() static

Santosh Sivaraj (4):
  powerpc/mce: Schedule work from irq_work
  extable: Add function to search only kernel exception table
  powerpc/mce: Handle UE event for memcpy_mcsafe
  powerpc: add machine check safe copy_to_user

 arch/powerpc/Kconfig                 |   1 +
 arch/powerpc/include/asm/mce.h       |   6 +-
 arch/powerpc/include/asm/string.h    |   2 +
 arch/powerpc/include/asm/uaccess.h   |  14 ++
 arch/powerpc/kernel/mce.c            |  31 +++-
 arch/powerpc/kernel/mce_power.c      |  70 ++++----
 arch/powerpc/lib/Makefile            |   2 +-
 arch/powerpc/lib/memcpy_mcsafe_64.S  | 242 +++++++++++++++++++++++++++
 arch/powerpc/platforms/pseries/ras.c |   9 +-
 include/linux/extable.h              |   2 +
 kernel/extable.c                     |  11 +-
 11 files changed, 347 insertions(+), 43 deletions(-)
 create mode 100644 arch/powerpc/lib/memcpy_mcsafe_64.S

-- 
2.21.0

[PATCH v9 1/7] powerpc/mce: Schedule work from irq_work

[Santosh Sivaraj]

schedule_work() cannot be called from MCE exception context as MCE can
interrupt even in interrupt disabled context.

fixes: 733e4a4c ("powerpc/mce: hookup memory_failure for UE errors")
Suggested-by: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
Signed-off-by: Santosh Sivaraj <santosh@fossix.org>
Cc: stable@vger.kernel.org # v4.15+
---
 arch/powerpc/kernel/mce.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/kernel/mce.c b/arch/powerpc/kernel/mce.c
index b18df633eae9..cff31d4a501f 100644
--- a/arch/powerpc/kernel/mce.c
+++ b/arch/powerpc/kernel/mce.c
@@ -33,6 +33,7 @@ static DEFINE_PER_CPU(struct machine_check_event[MAX_MC_EVT],
 					mce_ue_event_queue);
 
 static void machine_check_process_queued_event(struct irq_work *work);
+static void machine_check_ue_irq_work(struct irq_work *work);
 void machine_check_ue_event(struct machine_check_event *evt);
 static void machine_process_ue_event(struct work_struct *work);
 
@@ -40,6 +41,10 @@ static struct irq_work mce_event_process_work = {
         .func = machine_check_process_queued_event,
 };
 
+static struct irq_work mce_ue_event_irq_work = {
+	.func = machine_check_ue_irq_work,
+};
+
 DECLARE_WORK(mce_ue_event_work, machine_process_ue_event);
 
 static void mce_set_error_info(struct machine_check_event *mce,
@@ -199,6 +204,10 @@ void release_mce_event(void)
 	get_mce_event(NULL, true);
 }
 
+static void machine_check_ue_irq_work(struct irq_work *work)
+{
+	schedule_work(&mce_ue_event_work);
+}
 
 /*
  * Queue up the MCE event which then can be handled later.
@@ -216,7 +225,7 @@ void machine_check_ue_event(struct machine_check_event *evt)
 	memcpy(this_cpu_ptr(&mce_ue_event_queue[index]), evt, sizeof(*evt));
 
 	/* Queue work to process this event later. */
-	schedule_work(&mce_ue_event_work);
+	irq_work_queue(&mce_ue_event_irq_work);
 }
 
 /*
-- 
2.21.0

[PATCH v9 2/7] powerpc/mce: Fix MCE handling for huge pages

[Santosh Sivaraj]

From: Balbir Singh <bsingharora@gmail.com>

The current code would fail on huge pages addresses, since the shift would
be incorrect. Use the correct page shift value returned by
__find_linux_pte() to get the correct physical address. The code is more
generic and can handle both regular and compound pages.

Fixes: ba41e1e1ccb9 ("powerpc/mce: Hookup derror (load/store) UE errors")
Signed-off-by: Balbir Singh <bsingharora@gmail.com>
[arbab@linux.ibm.com: Fixup pseries_do_memory_failure()]
Signed-off-by: Reza Arbab <arbab@linux.ibm.com>
Co-developed-by: Santosh Sivaraj <santosh@fossix.org>
Signed-off-by: Santosh Sivaraj <santosh@fossix.org>
Tested-by: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
Cc: stable@vger.kernel.org # v4.15+
---
 arch/powerpc/include/asm/mce.h       |  2 +-
 arch/powerpc/kernel/mce_power.c      | 55 ++++++++++++++--------------
 arch/powerpc/platforms/pseries/ras.c |  9 ++---
 3 files changed, 32 insertions(+), 34 deletions(-)

diff --git a/arch/powerpc/include/asm/mce.h b/arch/powerpc/include/asm/mce.h
index a4c6a74ad2fb..f3a6036b6bc0 100644
--- a/arch/powerpc/include/asm/mce.h
+++ b/arch/powerpc/include/asm/mce.h
@@ -209,7 +209,7 @@ extern void release_mce_event(void);
 extern void machine_check_queue_event(void);
 extern void machine_check_print_event_info(struct machine_check_event *evt,
 					   bool user_mode, bool in_guest);
-unsigned long addr_to_pfn(struct pt_regs *regs, unsigned long addr);
+unsigned long addr_to_phys(struct pt_regs *regs, unsigned long addr);
 #ifdef CONFIG_PPC_BOOK3S_64
 void flush_and_reload_slb(void);
 #endif /* CONFIG_PPC_BOOK3S_64 */
diff --git a/arch/powerpc/kernel/mce_power.c b/arch/powerpc/kernel/mce_power.c
index a814d2dfb5b0..e74816f045f8 100644
--- a/arch/powerpc/kernel/mce_power.c
+++ b/arch/powerpc/kernel/mce_power.c
@@ -20,13 +20,14 @@
 #include <asm/exception-64s.h>
 
 /*
- * Convert an address related to an mm to a PFN. NOTE: we are in real
- * mode, we could potentially race with page table updates.
+ * Convert an address related to an mm to a physical address.
+ * NOTE: we are in real mode, we could potentially race with page table updates.
  */
-unsigned long addr_to_pfn(struct pt_regs *regs, unsigned long addr)
+unsigned long addr_to_phys(struct pt_regs *regs, unsigned long addr)
 {
-	pte_t *ptep;
-	unsigned long flags;
+	pte_t *ptep, pte;
+	unsigned int shift;
+	unsigned long flags, phys_addr;
 	struct mm_struct *mm;
 
 	if (user_mode(regs))
@@ -35,14 +36,21 @@ unsigned long addr_to_pfn(struct pt_regs *regs, unsigned long addr)
 		mm = &init_mm;
 
 	local_irq_save(flags);
-	if (mm == current->mm)
-		ptep = find_current_mm_pte(mm->pgd, addr, NULL, NULL);
-	else
-		ptep = find_init_mm_pte(addr, NULL);
+	ptep = __find_linux_pte(mm->pgd, addr, NULL, &shift);
 	local_irq_restore(flags);
+
 	if (!ptep || pte_special(*ptep))
 		return ULONG_MAX;
-	return pte_pfn(*ptep);
+
+	pte = *ptep;
+	if (shift > PAGE_SHIFT) {
+		unsigned long rpnmask = (1ul << shift) - PAGE_SIZE;
+
+		pte = __pte(pte_val(pte) | (addr & rpnmask));
+	}
+	phys_addr = pte_pfn(pte) << PAGE_SHIFT;
+
+	return phys_addr;
 }
 
 /* flush SLBs and reload */
@@ -344,7 +352,7 @@ static const struct mce_derror_table mce_p9_derror_table[] = {
   MCE_INITIATOR_CPU,   MCE_SEV_SEVERE, true },
 { 0, false, 0, 0, 0, 0, 0 } };
 
-static int mce_find_instr_ea_and_pfn(struct pt_regs *regs, uint64_t *addr,
+static int mce_find_instr_ea_and_phys(struct pt_regs *regs, uint64_t *addr,
 					uint64_t *phys_addr)
 {
 	/*
@@ -354,18 +362,16 @@ static int mce_find_instr_ea_and_pfn(struct pt_regs *regs, uint64_t *addr,
 	 * faults
 	 */
 	int instr;
-	unsigned long pfn, instr_addr;
+	unsigned long instr_addr;
 	struct instruction_op op;
 	struct pt_regs tmp = *regs;
 
-	pfn = addr_to_pfn(regs, regs->nip);
-	if (pfn != ULONG_MAX) {
-		instr_addr = (pfn << PAGE_SHIFT) + (regs->nip & ~PAGE_MASK);
+	instr_addr = addr_to_phys(regs, regs->nip) + (regs->nip & ~PAGE_MASK);
+	if (instr_addr != ULONG_MAX) {
 		instr = *(unsigned int *)(instr_addr);
 		if (!analyse_instr(&op, &tmp, instr)) {
-			pfn = addr_to_pfn(regs, op.ea);
 			*addr = op.ea;
-			*phys_addr = (pfn << PAGE_SHIFT);
+			*phys_addr = addr_to_phys(regs, op.ea);
 			return 0;
 		}
 		/*
@@ -440,15 +446,9 @@ static int mce_handle_ierror(struct pt_regs *regs,
 			*addr = regs->nip;
 			if (mce_err->sync_error &&
 				table[i].error_type == MCE_ERROR_TYPE_UE) {
-				unsigned long pfn;
-
-				if (get_paca()->in_mce < MAX_MCE_DEPTH) {
-					pfn = addr_to_pfn(regs, regs->nip);
-					if (pfn != ULONG_MAX) {
-						*phys_addr =
-							(pfn << PAGE_SHIFT);
-					}
-				}
+				if (get_paca()->in_mce < MAX_MCE_DEPTH)
+					*phys_addr = addr_to_phys(regs,
+								 regs->nip);
 			}
 		}
 		return handled;
@@ -541,7 +541,8 @@ static int mce_handle_derror(struct pt_regs *regs,
 			 * kernel/exception-64s.h
 			 */
 			if (get_paca()->in_mce < MAX_MCE_DEPTH)
-				mce_find_instr_ea_and_pfn(regs, addr, phys_addr);
+				mce_find_instr_ea_and_phys(regs, addr,
+							   phys_addr);
 		}
 		found = 1;
 	}
diff --git a/arch/powerpc/platforms/pseries/ras.c b/arch/powerpc/platforms/pseries/ras.c
index f16fdd0f71f7..5743f6353638 100644
--- a/arch/powerpc/platforms/pseries/ras.c
+++ b/arch/powerpc/platforms/pseries/ras.c
@@ -739,13 +739,10 @@ static void pseries_do_memory_failure(struct pt_regs *regs,
 	if (mce_log->sub_err_type & UE_LOGICAL_ADDR_PROVIDED) {
 		paddr = be64_to_cpu(mce_log->logical_address);
 	} else if (mce_log->sub_err_type & UE_EFFECTIVE_ADDR_PROVIDED) {
-		unsigned long pfn;
-
-		pfn = addr_to_pfn(regs,
-				  be64_to_cpu(mce_log->effective_address));
-		if (pfn == ULONG_MAX)
+		paddr = addr_to_phys(regs,
+				     be64_to_cpu(mce_log->effective_address));
+		if (paddr == ULONG_MAX)
 			return;
-		paddr = pfn << PAGE_SHIFT;
 	} else {
 		return;
 	}
-- 
2.21.0

[PATCH v9 3/7] powerpc/mce: Make machine_check_ue_event() static

[Santosh Sivaraj]

From: Reza Arbab <arbab@linux.ibm.com>

The function doesn't get used outside this file, so make it static.

Signed-off-by: Reza Arbab <arbab@linux.ibm.com>
Signed-off-by: Santosh Sivaraj <santosh@fossix.org>
Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
---
 arch/powerpc/kernel/mce.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/kernel/mce.c b/arch/powerpc/kernel/mce.c
index cff31d4a501f..a3b122a685a5 100644
--- a/arch/powerpc/kernel/mce.c
+++ b/arch/powerpc/kernel/mce.c
@@ -34,7 +34,7 @@ static DEFINE_PER_CPU(struct machine_check_event[MAX_MC_EVT],
 
 static void machine_check_process_queued_event(struct irq_work *work);
 static void machine_check_ue_irq_work(struct irq_work *work);
-void machine_check_ue_event(struct machine_check_event *evt);
+static void machine_check_ue_event(struct machine_check_event *evt);
 static void machine_process_ue_event(struct work_struct *work);
 
 static struct irq_work mce_event_process_work = {
@@ -212,7 +212,7 @@ static void machine_check_ue_irq_work(struct irq_work *work)
 /*
  * Queue up the MCE event which then can be handled later.
  */
-void machine_check_ue_event(struct machine_check_event *evt)
+static void machine_check_ue_event(struct machine_check_event *evt)
 {
 	int index;
 
-- 
2.21.0

[PATCH v9 4/7] extable: Add function to search only kernel exception table

[Santosh Sivaraj]

Certain architecture specific operating modes (e.g., in powerpc machine
check handler that is unable to access vmalloc memory), the
search_exception_tables cannot be called because it also searches the
module exception tables if entry is not found in the kernel exception
table.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Santosh Sivaraj <santosh@fossix.org>
Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
---
 include/linux/extable.h |  2 ++
 kernel/extable.c        | 11 +++++++++--
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/include/linux/extable.h b/include/linux/extable.h
index 41c5b3a25f67..81ecfaa83ad3 100644
--- a/include/linux/extable.h
+++ b/include/linux/extable.h
@@ -19,6 +19,8 @@ void trim_init_extable(struct module *m);
 
 /* Given an address, look for it in the exception tables */
 const struct exception_table_entry *search_exception_tables(unsigned long add);
+const struct exception_table_entry *
+search_kernel_exception_table(unsigned long addr);
 
 #ifdef CONFIG_MODULES
 /* For extable.c to search modules' exception tables. */
diff --git a/kernel/extable.c b/kernel/extable.c
index e23cce6e6092..f6c9406eec7d 100644
--- a/kernel/extable.c
+++ b/kernel/extable.c
@@ -40,13 +40,20 @@ void __init sort_main_extable(void)
 	}
 }
 
+/* Given an address, look for it in the kernel exception table */
+const
+struct exception_table_entry *search_kernel_exception_table(unsigned long addr)
+{
+	return search_extable(__start___ex_table,
+			      __stop___ex_table - __start___ex_table, addr);
+}
+
 /* Given an address, look for it in the exception tables. */
 const struct exception_table_entry *search_exception_tables(unsigned long addr)
 {
 	const struct exception_table_entry *e;
 
-	e = search_extable(__start___ex_table,
-			   __stop___ex_table - __start___ex_table, addr);
+	e = search_kernel_exception_table(addr);
 	if (!e)
 		e = search_module_extables(addr);
 	return e;
-- 
2.21.0

[PATCH v9 5/7] powerpc/memcpy: Add memcpy_mcsafe for pmem

[Santosh Sivaraj]

From: Balbir Singh <bsingharora@gmail.com>

The pmem infrastructure uses memcpy_mcsafe in the pmem layer so as to
convert machine check exceptions into a return value on failure in case
a machine check exception is encountered during the memcpy. The return
value is the number of bytes remaining to be copied.

This patch largely borrows from the copyuser_power7 logic and does not add
the VMX optimizations, largely to keep the patch simple. If needed those
optimizations can be folded in.

Signed-off-by: Balbir Singh <bsingharora@gmail.com>
[arbab@linux.ibm.com: Added symbol export]
Co-developed-by: Santosh Sivaraj <santosh@fossix.org>
Signed-off-by: Santosh Sivaraj <santosh@fossix.org>
---
 arch/powerpc/include/asm/string.h   |   2 +
 arch/powerpc/lib/Makefile           |   2 +-
 arch/powerpc/lib/memcpy_mcsafe_64.S | 242 ++++++++++++++++++++++++++++
 3 files changed, 245 insertions(+), 1 deletion(-)
 create mode 100644 arch/powerpc/lib/memcpy_mcsafe_64.S

diff --git a/arch/powerpc/include/asm/string.h b/arch/powerpc/include/asm/string.h
index 9bf6dffb4090..b72692702f35 100644
--- a/arch/powerpc/include/asm/string.h
+++ b/arch/powerpc/include/asm/string.h
@@ -53,7 +53,9 @@ void *__memmove(void *to, const void *from, __kernel_size_t n);
 #ifndef CONFIG_KASAN
 #define __HAVE_ARCH_MEMSET32
 #define __HAVE_ARCH_MEMSET64
+#define __HAVE_ARCH_MEMCPY_MCSAFE
 
+extern int memcpy_mcsafe(void *dst, const void *src, __kernel_size_t sz);
 extern void *__memset16(uint16_t *, uint16_t v, __kernel_size_t);
 extern void *__memset32(uint32_t *, uint32_t v, __kernel_size_t);
 extern void *__memset64(uint64_t *, uint64_t v, __kernel_size_t);
diff --git a/arch/powerpc/lib/Makefile b/arch/powerpc/lib/Makefile
index eebc782d89a5..fa6b1b657b43 100644
--- a/arch/powerpc/lib/Makefile
+++ b/arch/powerpc/lib/Makefile
@@ -39,7 +39,7 @@ obj-$(CONFIG_PPC_BOOK3S_64) += copyuser_power7.o copypage_power7.o \
 			       memcpy_power7.o
 
 obj64-y	+= copypage_64.o copyuser_64.o mem_64.o hweight_64.o \
-	   memcpy_64.o pmem.o
+	   memcpy_64.o pmem.o memcpy_mcsafe_64.o
 
 obj64-$(CONFIG_SMP)	+= locks.o
 obj64-$(CONFIG_ALTIVEC)	+= vmx-helper.o
diff --git a/arch/powerpc/lib/memcpy_mcsafe_64.S b/arch/powerpc/lib/memcpy_mcsafe_64.S
new file mode 100644
index 000000000000..949976dc115d
--- /dev/null
+++ b/arch/powerpc/lib/memcpy_mcsafe_64.S
@@ -0,0 +1,242 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) IBM Corporation, 2011
+ * Derived from copyuser_power7.s by Anton Blanchard <anton@au.ibm.com>
+ * Author - Balbir Singh <bsingharora@gmail.com>
+ */
+#include <asm/ppc_asm.h>
+#include <asm/errno.h>
+#include <asm/export.h>
+
+	.macro err1
+100:
+	EX_TABLE(100b,.Ldo_err1)
+	.endm
+
+	.macro err2
+200:
+	EX_TABLE(200b,.Ldo_err2)
+	.endm
+
+	.macro err3
+300:	EX_TABLE(300b,.Ldone)
+	.endm
+
+.Ldo_err2:
+	ld	r22,STK_REG(R22)(r1)
+	ld	r21,STK_REG(R21)(r1)
+	ld	r20,STK_REG(R20)(r1)
+	ld	r19,STK_REG(R19)(r1)
+	ld	r18,STK_REG(R18)(r1)
+	ld	r17,STK_REG(R17)(r1)
+	ld	r16,STK_REG(R16)(r1)
+	ld	r15,STK_REG(R15)(r1)
+	ld	r14,STK_REG(R14)(r1)
+	addi	r1,r1,STACKFRAMESIZE
+.Ldo_err1:
+	/* Do a byte by byte copy to get the exact remaining size */
+	mtctr	r7
+46:
+err3;	lbz	r0,0(r4)
+	addi	r4,r4,1
+err3;	stb	r0,0(r3)
+	addi	r3,r3,1
+	bdnz	46b
+	li	r3,0
+	blr
+
+.Ldone:
+	mfctr	r3
+	blr
+
+
+_GLOBAL(memcpy_mcsafe)
+	mr	r7,r5
+	cmpldi	r5,16
+	blt	.Lshort_copy
+
+.Lcopy:
+	/* Get the source 8B aligned */
+	neg	r6,r4
+	mtocrf	0x01,r6
+	clrldi	r6,r6,(64-3)
+
+	bf	cr7*4+3,1f
+err1;	lbz	r0,0(r4)
+	addi	r4,r4,1
+err1;	stb	r0,0(r3)
+	addi	r3,r3,1
+	subi	r7,r7,1
+
+1:	bf	cr7*4+2,2f
+err1;	lhz	r0,0(r4)
+	addi	r4,r4,2
+err1;	sth	r0,0(r3)
+	addi	r3,r3,2
+	subi	r7,r7,2
+
+2:	bf	cr7*4+1,3f
+err1;	lwz	r0,0(r4)
+	addi	r4,r4,4
+err1;	stw	r0,0(r3)
+	addi	r3,r3,4
+	subi	r7,r7,4
+
+3:	sub	r5,r5,r6
+	cmpldi	r5,128
+	blt	5f
+
+	mflr	r0
+	stdu	r1,-STACKFRAMESIZE(r1)
+	std	r14,STK_REG(R14)(r1)
+	std	r15,STK_REG(R15)(r1)
+	std	r16,STK_REG(R16)(r1)
+	std	r17,STK_REG(R17)(r1)
+	std	r18,STK_REG(R18)(r1)
+	std	r19,STK_REG(R19)(r1)
+	std	r20,STK_REG(R20)(r1)
+	std	r21,STK_REG(R21)(r1)
+	std	r22,STK_REG(R22)(r1)
+	std	r0,STACKFRAMESIZE+16(r1)
+
+	srdi	r6,r5,7
+	mtctr	r6
+
+	/* Now do cacheline (128B) sized loads and stores. */
+	.align	5
+4:
+err2;	ld	r0,0(r4)
+err2;	ld	r6,8(r4)
+err2;	ld	r8,16(r4)
+err2;	ld	r9,24(r4)
+err2;	ld	r10,32(r4)
+err2;	ld	r11,40(r4)
+err2;	ld	r12,48(r4)
+err2;	ld	r14,56(r4)
+err2;	ld	r15,64(r4)
+err2;	ld	r16,72(r4)
+err2;	ld	r17,80(r4)
+err2;	ld	r18,88(r4)
+err2;	ld	r19,96(r4)
+err2;	ld	r20,104(r4)
+err2;	ld	r21,112(r4)
+err2;	ld	r22,120(r4)
+	addi	r4,r4,128
+err2;	std	r0,0(r3)
+err2;	std	r6,8(r3)
+err2;	std	r8,16(r3)
+err2;	std	r9,24(r3)
+err2;	std	r10,32(r3)
+err2;	std	r11,40(r3)
+err2;	std	r12,48(r3)
+err2;	std	r14,56(r3)
+err2;	std	r15,64(r3)
+err2;	std	r16,72(r3)
+err2;	std	r17,80(r3)
+err2;	std	r18,88(r3)
+err2;	std	r19,96(r3)
+err2;	std	r20,104(r3)
+err2;	std	r21,112(r3)
+err2;	std	r22,120(r3)
+	addi	r3,r3,128
+	subi	r7,r7,128
+	bdnz	4b
+
+	clrldi	r5,r5,(64-7)
+
+	/* Up to 127B to go */
+5:	srdi	r6,r5,4
+	mtocrf	0x01,r6
+
+6:	bf	cr7*4+1,7f
+err2;	ld	r0,0(r4)
+err2;	ld	r6,8(r4)
+err2;	ld	r8,16(r4)
+err2;	ld	r9,24(r4)
+err2;	ld	r10,32(r4)
+err2;	ld	r11,40(r4)
+err2;	ld	r12,48(r4)
+err2;	ld	r14,56(r4)
+	addi	r4,r4,64
+err2;	std	r0,0(r3)
+err2;	std	r6,8(r3)
+err2;	std	r8,16(r3)
+err2;	std	r9,24(r3)
+err2;	std	r10,32(r3)
+err2;	std	r11,40(r3)
+err2;	std	r12,48(r3)
+err2;	std	r14,56(r3)
+	addi	r3,r3,64
+	subi	r7,r7,64
+
+7:	ld	r14,STK_REG(R14)(r1)
+	ld	r15,STK_REG(R15)(r1)
+	ld	r16,STK_REG(R16)(r1)
+	ld	r17,STK_REG(R17)(r1)
+	ld	r18,STK_REG(R18)(r1)
+	ld	r19,STK_REG(R19)(r1)
+	ld	r20,STK_REG(R20)(r1)
+	ld	r21,STK_REG(R21)(r1)
+	ld	r22,STK_REG(R22)(r1)
+	addi	r1,r1,STACKFRAMESIZE
+
+	/* Up to 63B to go */
+	bf	cr7*4+2,8f
+err1;	ld	r0,0(r4)
+err1;	ld	r6,8(r4)
+err1;	ld	r8,16(r4)
+err1;	ld	r9,24(r4)
+	addi	r4,r4,32
+err1;	std	r0,0(r3)
+err1;	std	r6,8(r3)
+err1;	std	r8,16(r3)
+err1;	std	r9,24(r3)
+	addi	r3,r3,32
+	subi	r7,r7,32
+
+	/* Up to 31B to go */
+8:	bf	cr7*4+3,9f
+err1;	ld	r0,0(r4)
+err1;	ld	r6,8(r4)
+	addi	r4,r4,16
+err1;	std	r0,0(r3)
+err1;	std	r6,8(r3)
+	addi	r3,r3,16
+	subi	r7,r7,16
+
+9:	clrldi	r5,r5,(64-4)
+
+	/* Up to 15B to go */
+.Lshort_copy:
+	mtocrf	0x01,r5
+	bf	cr7*4+0,12f
+err1;	lwz	r0,0(r4)	/* Less chance of a reject with word ops */
+err1;	lwz	r6,4(r4)
+	addi	r4,r4,8
+err1;	stw	r0,0(r3)
+err1;	stw	r6,4(r3)
+	addi	r3,r3,8
+	subi	r7,r7,8
+
+12:	bf	cr7*4+1,13f
+err1;	lwz	r0,0(r4)
+	addi	r4,r4,4
+err1;	stw	r0,0(r3)
+	addi	r3,r3,4
+	subi	r7,r7,4
+
+13:	bf	cr7*4+2,14f
+err1;	lhz	r0,0(r4)
+	addi	r4,r4,2
+err1;	sth	r0,0(r3)
+	addi	r3,r3,2
+	subi	r7,r7,2
+
+14:	bf	cr7*4+3,15f
+err1;	lbz	r0,0(r4)
+err1;	stb	r0,0(r3)
+
+15:	li	r3,0
+	blr
+
+EXPORT_SYMBOL_GPL(memcpy_mcsafe);
-- 
2.21.0

[PATCH v9 6/7] powerpc/mce: Handle UE event for memcpy_mcsafe

[Santosh Sivaraj]

If we take a UE on one of the instructions with a fixup entry, set nip
to continue execution at the fixup entry. Stop processing the event
further or print it.

Co-developed-by: Reza Arbab <arbab@linux.ibm.com>
Signed-off-by: Reza Arbab <arbab@linux.ibm.com>
Cc: Mahesh Salgaonkar <mahesh@linux.ibm.com>
Signed-off-by: Santosh Sivaraj <santosh@fossix.org>
---
 arch/powerpc/include/asm/mce.h  |  4 +++-
 arch/powerpc/kernel/mce.c       | 16 ++++++++++++++++
 arch/powerpc/kernel/mce_power.c | 15 +++++++++++++--
 3 files changed, 32 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/include/asm/mce.h b/arch/powerpc/include/asm/mce.h
index f3a6036b6bc0..e1931c8c2743 100644
--- a/arch/powerpc/include/asm/mce.h
+++ b/arch/powerpc/include/asm/mce.h
@@ -122,7 +122,8 @@ struct machine_check_event {
 			enum MCE_UeErrorType ue_error_type:8;
 			u8		effective_address_provided;
 			u8		physical_address_provided;
-			u8		reserved_1[5];
+			u8		ignore_event;
+			u8		reserved_1[4];
 			u64		effective_address;
 			u64		physical_address;
 			u8		reserved_2[8];
@@ -193,6 +194,7 @@ struct mce_error_info {
 	enum MCE_Initiator	initiator:8;
 	enum MCE_ErrorClass	error_class:8;
 	bool			sync_error;
+	bool			ignore_event;
 };
 
 #define MAX_MC_EVT	100
diff --git a/arch/powerpc/kernel/mce.c b/arch/powerpc/kernel/mce.c
index a3b122a685a5..ec4b3e1087be 100644
--- a/arch/powerpc/kernel/mce.c
+++ b/arch/powerpc/kernel/mce.c
@@ -149,6 +149,7 @@ void save_mce_event(struct pt_regs *regs, long handled,
 		if (phys_addr != ULONG_MAX) {
 			mce->u.ue_error.physical_address_provided = true;
 			mce->u.ue_error.physical_address = phys_addr;
+			mce->u.ue_error.ignore_event = mce_err->ignore_event;
 			machine_check_ue_event(mce);
 		}
 	}
@@ -266,8 +267,17 @@ static void machine_process_ue_event(struct work_struct *work)
 		/*
 		 * This should probably queued elsewhere, but
 		 * oh! well
+		 *
+		 * Don't report this machine check because the caller has a
+		 * asked us to ignore the event, it has a fixup handler which
+		 * will do the appropriate error handling and reporting.
 		 */
 		if (evt->error_type == MCE_ERROR_TYPE_UE) {
+			if (evt->u.ue_error.ignore_event) {
+				__this_cpu_dec(mce_ue_count);
+				continue;
+			}
+
 			if (evt->u.ue_error.physical_address_provided) {
 				unsigned long pfn;
 
@@ -301,6 +311,12 @@ static void machine_check_process_queued_event(struct irq_work *work)
 	while (__this_cpu_read(mce_queue_count) > 0) {
 		index = __this_cpu_read(mce_queue_count) - 1;
 		evt = this_cpu_ptr(&mce_event_queue[index]);
+
+		if (evt->error_type == MCE_ERROR_TYPE_UE &&
+		    evt->u.ue_error.ignore_event) {
+			__this_cpu_dec(mce_queue_count);
+			continue;
+		}
 		machine_check_print_event_info(evt, false, false);
 		__this_cpu_dec(mce_queue_count);
 	}
diff --git a/arch/powerpc/kernel/mce_power.c b/arch/powerpc/kernel/mce_power.c
index e74816f045f8..1dd87f6f5186 100644
--- a/arch/powerpc/kernel/mce_power.c
+++ b/arch/powerpc/kernel/mce_power.c
@@ -11,6 +11,7 @@
 
 #include <linux/types.h>
 #include <linux/ptrace.h>
+#include <linux/extable.h>
 #include <asm/mmu.h>
 #include <asm/mce.h>
 #include <asm/machdep.h>
@@ -18,6 +19,7 @@
 #include <asm/pte-walk.h>
 #include <asm/sstep.h>
 #include <asm/exception-64s.h>
+#include <asm/extable.h>
 
 /*
  * Convert an address related to an mm to a physical address.
@@ -559,9 +561,18 @@ static int mce_handle_derror(struct pt_regs *regs,
 	return 0;
 }
 
-static long mce_handle_ue_error(struct pt_regs *regs)
+static long mce_handle_ue_error(struct pt_regs *regs,
+				struct mce_error_info *mce_err)
 {
 	long handled = 0;
+	const struct exception_table_entry *entry;
+
+	entry = search_kernel_exception_table(regs->nip);
+	if (entry) {
+		mce_err->ignore_event = true;
+		regs->nip = extable_fixup(entry);
+		return 1;
+	}
 
 	/*
 	 * On specific SCOM read via MMIO we may get a machine check
@@ -594,7 +605,7 @@ static long mce_handle_error(struct pt_regs *regs,
 				&phys_addr);
 
 	if (!handled && mce_err.error_type == MCE_ERROR_TYPE_UE)
-		handled = mce_handle_ue_error(regs);
+		handled = mce_handle_ue_error(regs, &mce_err);
 
 	save_mce_event(regs, handled, &mce_err, regs->nip, addr, phys_addr);
 
-- 
2.21.0

[PATCH v9 7/7] powerpc: add machine check safe copy_to_user

[Santosh Sivaraj]

Use  memcpy_mcsafe() implementation to define copy_to_user_mcsafe()

Signed-off-by: Santosh Sivaraj <santosh@fossix.org>
---
 arch/powerpc/Kconfig               |  1 +
 arch/powerpc/include/asm/uaccess.h | 14 ++++++++++++++
 2 files changed, 15 insertions(+)

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 77f6ebf97113..4316e36095a2 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -137,6 +137,7 @@ config PPC
 	select ARCH_HAS_STRICT_KERNEL_RWX	if ((PPC_BOOK3S_64 || PPC32) && !RELOCATABLE && !HIBERNATION)
 	select ARCH_HAS_TICK_BROADCAST		if GENERIC_CLOCKEVENTS_BROADCAST
 	select ARCH_HAS_UACCESS_FLUSHCACHE	if PPC64
+	select ARCH_HAS_UACCESS_MCSAFE		if PPC64
 	select ARCH_HAS_UBSAN_SANITIZE_ALL
 	select ARCH_HAVE_NMI_SAFE_CMPXCHG
 	select ARCH_KEEP_MEMBLOCK
diff --git a/arch/powerpc/include/asm/uaccess.h b/arch/powerpc/include/asm/uaccess.h
index 8b03eb44e876..15002b51ff18 100644
--- a/arch/powerpc/include/asm/uaccess.h
+++ b/arch/powerpc/include/asm/uaccess.h
@@ -387,6 +387,20 @@ static inline unsigned long raw_copy_to_user(void __user *to,
 	return ret;
 }
 
+static __always_inline unsigned long __must_check
+copy_to_user_mcsafe(void __user *to, const void *from, unsigned long n)
+{
+	if (likely(check_copy_size(from, n, true))) {
+		if (access_ok(to, n)) {
+			allow_write_to_user(to, n);
+			n = memcpy_mcsafe((void *)to, from, n);
+			prevent_write_to_user(to, n);
+		}
+	}
+
+	return n;
+}
+
 extern unsigned long __clear_user(void __user *addr, unsigned long size);
 
 static inline unsigned long clear_user(void __user *addr, unsigned long size)
-- 
2.21.0

Re: [PATCH v9 2/7] powerpc/mce: Fix MCE handling for huge pages

[Sasha Levin]

Hi,

[This is an automated email]

This commit has been processed because it contains a "Fixes:" tag,
fixing commit: ba41e1e1ccb9 powerpc/mce: Hookup derror (load/store) UE errors.

The bot has tested the following trees: v5.2.8, v4.19.66.

v5.2.8: Build OK!
v4.19.66: Failed to apply! Possible dependencies:
    360cae313702 ("KVM: PPC: Book3S HV: Nested guest entry via hypercall")
    41f4e631daf8 ("KVM: PPC: Book3S HV: Extract PMU save/restore operations as C-callable functions")
    884dfb722db8 ("KVM: PPC: Book3S HV: Simplify machine check handling")
    89329c0be8bd ("KVM: PPC: Book3S HV: Clear partition table entry on vm teardown")
    8e3f5fc1045d ("KVM: PPC: Book3S HV: Framework and hcall stubs for nested virtualization")
    95a6432ce903 ("KVM: PPC: Book3S HV: Streamlined guest entry/exit path on P9 for radix guests")
    a43c1590426c ("powerpc/pseries: Flush SLB contents on SLB MCE errors.")
    c05772018491 ("powerpc/64s: Better printing of machine check info for guest MCEs")
    d24ea8a7336a ("KVM: PPC: Book3S: Simplify external interrupt handling")
    df709a296ef7 ("KVM: PPC: Book3S HV: Simplify real-mode interrupt handling")
    f7035ce9f1df ("KVM: PPC: Book3S HV: Move interrupt delivery on guest entry to C code")


NOTE: The patch will not be queued to stable trees until it is upstream.

How should we proceed with this patch?

--
Thanks,
Sasha

Re: [PATCH v9 2/7] powerpc/mce: Fix MCE handling for huge pages

[Santosh Sivaraj]

Sasha Levin <sashal@kernel.org> writes:

> Hi,
>
> [This is an automated email]
>
> This commit has been processed because it contains a "Fixes:" tag,
> fixing commit: ba41e1e1ccb9 powerpc/mce: Hookup derror (load/store) UE errors.
>
> The bot has tested the following trees: v5.2.8, v4.19.66.
>
> v5.2.8: Build OK!
> v4.19.66: Failed to apply! Possible dependencies:
>     360cae313702 ("KVM: PPC: Book3S HV: Nested guest entry via hypercall")
>     41f4e631daf8 ("KVM: PPC: Book3S HV: Extract PMU save/restore operations as C-callable functions")
>     884dfb722db8 ("KVM: PPC: Book3S HV: Simplify machine check handling")
>     89329c0be8bd ("KVM: PPC: Book3S HV: Clear partition table entry on vm teardown")
>     8e3f5fc1045d ("KVM: PPC: Book3S HV: Framework and hcall stubs for nested virtualization")
>     95a6432ce903 ("KVM: PPC: Book3S HV: Streamlined guest entry/exit path on P9 for radix guests")
>     a43c1590426c ("powerpc/pseries: Flush SLB contents on SLB MCE errors.")
>     c05772018491 ("powerpc/64s: Better printing of machine check info for guest MCEs")
>     d24ea8a7336a ("KVM: PPC: Book3S: Simplify external interrupt handling")
>     df709a296ef7 ("KVM: PPC: Book3S HV: Simplify real-mode interrupt handling")
>     f7035ce9f1df ("KVM: PPC: Book3S HV: Move interrupt delivery on guest entry to C code")
>
>
> NOTE: The patch will not be queued to stable trees until it is upstream.
>
> How should we proceed with this patch?

I will send a backport once this has been merged upstream.

Thanks,
Santosh

>
> --
> Thanks,
> Sasha

Re: [PATCH v9 1/7] powerpc/mce: Schedule work from irq_work

[Mahesh Jagannath Salgaonkar]

On 8/12/19 2:52 PM, Santosh Sivaraj wrote:
> schedule_work() cannot be called from MCE exception context as MCE can
> interrupt even in interrupt disabled context.
> 
> fixes: 733e4a4c ("powerpc/mce: hookup memory_failure for UE errors")
> Suggested-by: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
> Signed-off-by: Santosh Sivaraj <santosh@fossix.org>
> Cc: stable@vger.kernel.org # v4.15+
> ---
>  arch/powerpc/kernel/mce.c | 11 ++++++++++-
>  1 file changed, 10 insertions(+), 1 deletion(-)

Reviewed-by: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>

Thanks,
-Mahesh.

> 
> diff --git a/arch/powerpc/kernel/mce.c b/arch/powerpc/kernel/mce.c
> index b18df633eae9..cff31d4a501f 100644
> --- a/arch/powerpc/kernel/mce.c
> +++ b/arch/powerpc/kernel/mce.c
> @@ -33,6 +33,7 @@ static DEFINE_PER_CPU(struct machine_check_event[MAX_MC_EVT],
>  					mce_ue_event_queue);
>  
>  static void machine_check_process_queued_event(struct irq_work *work);
> +static void machine_check_ue_irq_work(struct irq_work *work);
>  void machine_check_ue_event(struct machine_check_event *evt);
>  static void machine_process_ue_event(struct work_struct *work);
>  
> @@ -40,6 +41,10 @@ static struct irq_work mce_event_process_work = {
>          .func = machine_check_process_queued_event,
>  };
>  
> +static struct irq_work mce_ue_event_irq_work = {
> +	.func = machine_check_ue_irq_work,
> +};
> +
>  DECLARE_WORK(mce_ue_event_work, machine_process_ue_event);
>  
>  static void mce_set_error_info(struct machine_check_event *mce,
> @@ -199,6 +204,10 @@ void release_mce_event(void)
>  	get_mce_event(NULL, true);
>  }
>  
> +static void machine_check_ue_irq_work(struct irq_work *work)
> +{
> +	schedule_work(&mce_ue_event_work);
> +}
>  
>  /*
>   * Queue up the MCE event which then can be handled later.
> @@ -216,7 +225,7 @@ void machine_check_ue_event(struct machine_check_event *evt)
>  	memcpy(this_cpu_ptr(&mce_ue_event_queue[index]), evt, sizeof(*evt));
>  
>  	/* Queue work to process this event later. */
> -	schedule_work(&mce_ue_event_work);
> +	irq_work_queue(&mce_ue_event_irq_work);
>  }
>  
>  /*
> 

Re: [PATCH v9 6/7] powerpc/mce: Handle UE event for memcpy_mcsafe

[Mahesh Jagannath Salgaonkar]

On 8/12/19 2:52 PM, Santosh Sivaraj wrote:
> If we take a UE on one of the instructions with a fixup entry, set nip
> to continue execution at the fixup entry. Stop processing the event
> further or print it.
> 
> Co-developed-by: Reza Arbab <arbab@linux.ibm.com>
> Signed-off-by: Reza Arbab <arbab@linux.ibm.com>
> Cc: Mahesh Salgaonkar <mahesh@linux.ibm.com>
> Signed-off-by: Santosh Sivaraj <santosh@fossix.org>

Looks good to me.

Reviewed-by: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>

Thanks,
-Mahesh.

> ---
>  arch/powerpc/include/asm/mce.h  |  4 +++-
>  arch/powerpc/kernel/mce.c       | 16 ++++++++++++++++
>  arch/powerpc/kernel/mce_power.c | 15 +++++++++++++--
>  3 files changed, 32 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/mce.h b/arch/powerpc/include/asm/mce.h
> index f3a6036b6bc0..e1931c8c2743 100644
> --- a/arch/powerpc/include/asm/mce.h
> +++ b/arch/powerpc/include/asm/mce.h
> @@ -122,7 +122,8 @@ struct machine_check_event {
>  			enum MCE_UeErrorType ue_error_type:8;
>  			u8		effective_address_provided;
>  			u8		physical_address_provided;
> -			u8		reserved_1[5];
> +			u8		ignore_event;
> +			u8		reserved_1[4];
>  			u64		effective_address;
>  			u64		physical_address;
>  			u8		reserved_2[8];
> @@ -193,6 +194,7 @@ struct mce_error_info {
>  	enum MCE_Initiator	initiator:8;
>  	enum MCE_ErrorClass	error_class:8;
>  	bool			sync_error;
> +	bool			ignore_event;
>  };
>  
>  #define MAX_MC_EVT	100
> diff --git a/arch/powerpc/kernel/mce.c b/arch/powerpc/kernel/mce.c
> index a3b122a685a5..ec4b3e1087be 100644
> --- a/arch/powerpc/kernel/mce.c
> +++ b/arch/powerpc/kernel/mce.c
> @@ -149,6 +149,7 @@ void save_mce_event(struct pt_regs *regs, long handled,
>  		if (phys_addr != ULONG_MAX) {
>  			mce->u.ue_error.physical_address_provided = true;
>  			mce->u.ue_error.physical_address = phys_addr;
> +			mce->u.ue_error.ignore_event = mce_err->ignore_event;
>  			machine_check_ue_event(mce);
>  		}
>  	}
> @@ -266,8 +267,17 @@ static void machine_process_ue_event(struct work_struct *work)
>  		/*
>  		 * This should probably queued elsewhere, but
>  		 * oh! well
> +		 *
> +		 * Don't report this machine check because the caller has a
> +		 * asked us to ignore the event, it has a fixup handler which
> +		 * will do the appropriate error handling and reporting.
>  		 */
>  		if (evt->error_type == MCE_ERROR_TYPE_UE) {
> +			if (evt->u.ue_error.ignore_event) {
> +				__this_cpu_dec(mce_ue_count);
> +				continue;
> +			}
> +
>  			if (evt->u.ue_error.physical_address_provided) {
>  				unsigned long pfn;
>  
> @@ -301,6 +311,12 @@ static void machine_check_process_queued_event(struct irq_work *work)
>  	while (__this_cpu_read(mce_queue_count) > 0) {
>  		index = __this_cpu_read(mce_queue_count) - 1;
>  		evt = this_cpu_ptr(&mce_event_queue[index]);
> +
> +		if (evt->error_type == MCE_ERROR_TYPE_UE &&
> +		    evt->u.ue_error.ignore_event) {
> +			__this_cpu_dec(mce_queue_count);
> +			continue;
> +		}
>  		machine_check_print_event_info(evt, false, false);
>  		__this_cpu_dec(mce_queue_count);
>  	}
> diff --git a/arch/powerpc/kernel/mce_power.c b/arch/powerpc/kernel/mce_power.c
> index e74816f045f8..1dd87f6f5186 100644
> --- a/arch/powerpc/kernel/mce_power.c
> +++ b/arch/powerpc/kernel/mce_power.c
> @@ -11,6 +11,7 @@
>  
>  #include <linux/types.h>
>  #include <linux/ptrace.h>
> +#include <linux/extable.h>
>  #include <asm/mmu.h>
>  #include <asm/mce.h>
>  #include <asm/machdep.h>
> @@ -18,6 +19,7 @@
>  #include <asm/pte-walk.h>
>  #include <asm/sstep.h>
>  #include <asm/exception-64s.h>
> +#include <asm/extable.h>
>  
>  /*
>   * Convert an address related to an mm to a physical address.
> @@ -559,9 +561,18 @@ static int mce_handle_derror(struct pt_regs *regs,
>  	return 0;
>  }
>  
> -static long mce_handle_ue_error(struct pt_regs *regs)
> +static long mce_handle_ue_error(struct pt_regs *regs,
> +				struct mce_error_info *mce_err)
>  {
>  	long handled = 0;
> +	const struct exception_table_entry *entry;
> +
> +	entry = search_kernel_exception_table(regs->nip);
> +	if (entry) {
> +		mce_err->ignore_event = true;
> +		regs->nip = extable_fixup(entry);
> +		return 1;
> +	}
>  
>  	/*
>  	 * On specific SCOM read via MMIO we may get a machine check
> @@ -594,7 +605,7 @@ static long mce_handle_error(struct pt_regs *regs,
>  				&phys_addr);
>  
>  	if (!handled && mce_err.error_type == MCE_ERROR_TYPE_UE)
> -		handled = mce_handle_ue_error(regs);
> +		handled = mce_handle_ue_error(regs, &mce_err);
>  
>  	save_mce_event(regs, handled, &mce_err, regs->nip, addr, phys_addr);
>  
> 

Re: [PATCH v9 1/7] powerpc/mce: Schedule work from irq_work

[Balbir Singh]

On 12/8/19 7:22 pm, Santosh Sivaraj wrote:
> schedule_work() cannot be called from MCE exception context as MCE can
> interrupt even in interrupt disabled context.
> 
> fixes: 733e4a4c ("powerpc/mce: hookup memory_failure for UE errors")
> Suggested-by: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
> Signed-off-by: Santosh Sivaraj <santosh@fossix.org>
> Cc: stable@vger.kernel.org # v4.15+
> ---

Acked-by: Balbir Singh <bsingharora@gmail.com>

Re: [PATCH v9 4/7] extable: Add function to search only kernel exception table

[Balbir Singh]

On 12/8/19 7:22 pm, Santosh Sivaraj wrote:
> Certain architecture specific operating modes (e.g., in powerpc machine
> check handler that is unable to access vmalloc memory), the
> search_exception_tables cannot be called because it also searches the
> module exception tables if entry is not found in the kernel exception
> table.
> 
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@kernel.org>
> Cc: Nicholas Piggin <npiggin@gmail.com>
> Signed-off-by: Santosh Sivaraj <santosh@fossix.org>
> Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
> ---
>  include/linux/extable.h |  2 ++
>  kernel/extable.c        | 11 +++++++++--
>  2 files changed, 11 insertions(+), 2 deletions(-)
> 
> diff --git a/include/linux/extable.h b/include/linux/extable.h
> index 41c5b3a25f67..81ecfaa83ad3 100644
> --- a/include/linux/extable.h
> +++ b/include/linux/extable.h
> @@ -19,6 +19,8 @@ void trim_init_extable(struct module *m);
>  
>  /* Given an address, look for it in the exception tables */
>  const struct exception_table_entry *search_exception_tables(unsigned long add);
> +const struct exception_table_entry *
> +search_kernel_exception_table(unsigned long addr);
> 

Can we find a better name search_kernel still sounds like all of the kernel.
Can we rename it to search_kernel_linear_map_extable?

 
>  #ifdef CONFIG_MODULES
>  /* For extable.c to search modules' exception tables. */
> diff --git a/kernel/extable.c b/kernel/extable.c
> index e23cce6e6092..f6c9406eec7d 100644
> --- a/kernel/extable.c
> +++ b/kernel/extable.c
> @@ -40,13 +40,20 @@ void __init sort_main_extable(void)
>  	}
>  }
>  
> +/* Given an address, look for it in the kernel exception table */
> +const
> +struct exception_table_entry *search_kernel_exception_table(unsigned long addr)
> +{
> +	return search_extable(__start___ex_table,
> +			      __stop___ex_table - __start___ex_table, addr);
> +}
> +
>  /* Given an address, look for it in the exception tables. */
>  const struct exception_table_entry *search_exception_tables(unsigned long addr)
>  {
>  	const struct exception_table_entry *e;
>  
> -	e = search_extable(__start___ex_table,
> -			   __stop___ex_table - __start___ex_table, addr);
> +	e = search_kernel_exception_table(addr);
>  	if (!e)
>  		e = search_module_extables(addr);
>  	return e;
> 

Re: [PATCH v9 6/7] powerpc/mce: Handle UE event for memcpy_mcsafe

[Balbir Singh]

On 12/8/19 7:22 pm, Santosh Sivaraj wrote:
> If we take a UE on one of the instructions with a fixup entry, set nip
> to continue execution at the fixup entry. Stop processing the event
> further or print it.
> 
> Co-developed-by: Reza Arbab <arbab@linux.ibm.com>
> Signed-off-by: Reza Arbab <arbab@linux.ibm.com>
> Cc: Mahesh Salgaonkar <mahesh@linux.ibm.com>
> Signed-off-by: Santosh Sivaraj <santosh@fossix.org>
> ---

Isn't this based on https://patchwork.ozlabs.org/patch/895294/? If so it should still have my author tag and signed-off-by

Balbir Singh

>  arch/powerpc/include/asm/mce.h  |  4 +++-
>  arch/powerpc/kernel/mce.c       | 16 ++++++++++++++++
>  arch/powerpc/kernel/mce_power.c | 15 +++++++++++++--
>  3 files changed, 32 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/mce.h b/arch/powerpc/include/asm/mce.h
> index f3a6036b6bc0..e1931c8c2743 100644
> --- a/arch/powerpc/include/asm/mce.h
> +++ b/arch/powerpc/include/asm/mce.h
> @@ -122,7 +122,8 @@ struct machine_check_event {
>  			enum MCE_UeErrorType ue_error_type:8;
>  			u8		effective_address_provided;
>  			u8		physical_address_provided;
> -			u8		reserved_1[5];
> +			u8		ignore_event;
> +			u8		reserved_1[4];
>  			u64		effective_address;
>  			u64		physical_address;
>  			u8		reserved_2[8];
> @@ -193,6 +194,7 @@ struct mce_error_info {
>  	enum MCE_Initiator	initiator:8;
>  	enum MCE_ErrorClass	error_class:8;
>  	bool			sync_error;
> +	bool			ignore_event;
>  };
>  
>  #define MAX_MC_EVT	100
> diff --git a/arch/powerpc/kernel/mce.c b/arch/powerpc/kernel/mce.c
> index a3b122a685a5..ec4b3e1087be 100644
> --- a/arch/powerpc/kernel/mce.c
> +++ b/arch/powerpc/kernel/mce.c
> @@ -149,6 +149,7 @@ void save_mce_event(struct pt_regs *regs, long handled,
>  		if (phys_addr != ULONG_MAX) {
>  			mce->u.ue_error.physical_address_provided = true;
>  			mce->u.ue_error.physical_address = phys_addr;
> +			mce->u.ue_error.ignore_event = mce_err->ignore_event;
>  			machine_check_ue_event(mce);
>  		}
>  	}
> @@ -266,8 +267,17 @@ static void machine_process_ue_event(struct work_struct *work)
>  		/*
>  		 * This should probably queued elsewhere, but
>  		 * oh! well
> +		 *
> +		 * Don't report this machine check because the caller has a
> +		 * asked us to ignore the event, it has a fixup handler which
> +		 * will do the appropriate error handling and reporting.
>  		 */
>  		if (evt->error_type == MCE_ERROR_TYPE_UE) {
> +			if (evt->u.ue_error.ignore_event) {
> +				__this_cpu_dec(mce_ue_count);
> +				continue;
> +			}
> +
>  			if (evt->u.ue_error.physical_address_provided) {
>  				unsigned long pfn;
>  
> @@ -301,6 +311,12 @@ static void machine_check_process_queued_event(struct irq_work *work)
>  	while (__this_cpu_read(mce_queue_count) > 0) {
>  		index = __this_cpu_read(mce_queue_count) - 1;
>  		evt = this_cpu_ptr(&mce_event_queue[index]);
> +
> +		if (evt->error_type == MCE_ERROR_TYPE_UE &&
> +		    evt->u.ue_error.ignore_event) {
> +			__this_cpu_dec(mce_queue_count);
> +			continue;
> +		}
>  		machine_check_print_event_info(evt, false, false);
>  		__this_cpu_dec(mce_queue_count);
>  	}
> diff --git a/arch/powerpc/kernel/mce_power.c b/arch/powerpc/kernel/mce_power.c
> index e74816f045f8..1dd87f6f5186 100644
> --- a/arch/powerpc/kernel/mce_power.c
> +++ b/arch/powerpc/kernel/mce_power.c
> @@ -11,6 +11,7 @@
>  
>  #include <linux/types.h>
>  #include <linux/ptrace.h>
> +#include <linux/extable.h>
>  #include <asm/mmu.h>
>  #include <asm/mce.h>
>  #include <asm/machdep.h>
> @@ -18,6 +19,7 @@
>  #include <asm/pte-walk.h>
>  #include <asm/sstep.h>
>  #include <asm/exception-64s.h>
> +#include <asm/extable.h>
>  
>  /*
>   * Convert an address related to an mm to a physical address.
> @@ -559,9 +561,18 @@ static int mce_handle_derror(struct pt_regs *regs,
>  	return 0;
>  }
>  
> -static long mce_handle_ue_error(struct pt_regs *regs)
> +static long mce_handle_ue_error(struct pt_regs *regs,
> +				struct mce_error_info *mce_err)
>  {
>  	long handled = 0;
> +	const struct exception_table_entry *entry;
> +
> +	entry = search_kernel_exception_table(regs->nip);
> +	if (entry) {
> +		mce_err->ignore_event = true;
> +		regs->nip = extable_fixup(entry);
> +		return 1;
> +	}
>  
>  	/*
>  	 * On specific SCOM read via MMIO we may get a machine check
> @@ -594,7 +605,7 @@ static long mce_handle_error(struct pt_regs *regs,
>  				&phys_addr);
>  
>  	if (!handled && mce_err.error_type == MCE_ERROR_TYPE_UE)
> -		handled = mce_handle_ue_error(regs);
> +		handled = mce_handle_ue_error(regs, &mce_err);
>  
>  	save_mce_event(regs, handled, &mce_err, regs->nip, addr, phys_addr);
>  
> 

Re: [PATCH v9 4/7] extable: Add function to search only kernel exception table

[Santosh Sivaraj]

Balbir Singh <bsingharora@gmail.com> writes:

> On 12/8/19 7:22 pm, Santosh Sivaraj wrote:
>> Certain architecture specific operating modes (e.g., in powerpc machine
>> check handler that is unable to access vmalloc memory), the
>> search_exception_tables cannot be called because it also searches the
>> module exception tables if entry is not found in the kernel exception
>> table.
>> 
>> Cc: Thomas Gleixner <tglx@linutronix.de>
>> Cc: Ingo Molnar <mingo@kernel.org>
>> Cc: Nicholas Piggin <npiggin@gmail.com>
>> Signed-off-by: Santosh Sivaraj <santosh@fossix.org>
>> Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
>> ---
>>  include/linux/extable.h |  2 ++
>>  kernel/extable.c        | 11 +++++++++--
>>  2 files changed, 11 insertions(+), 2 deletions(-)
>> 
>> diff --git a/include/linux/extable.h b/include/linux/extable.h
>> index 41c5b3a25f67..81ecfaa83ad3 100644
>> --- a/include/linux/extable.h
>> +++ b/include/linux/extable.h
>> @@ -19,6 +19,8 @@ void trim_init_extable(struct module *m);
>>  
>>  /* Given an address, look for it in the exception tables */
>>  const struct exception_table_entry *search_exception_tables(unsigned long add);
>> +const struct exception_table_entry *
>> +search_kernel_exception_table(unsigned long addr);
>> 
>
> Can we find a better name search_kernel still sounds like all of the kernel.
> Can we rename it to search_kernel_linear_map_extable?

I thought search_kernel_exception_table and search_module_extables were
non-ambiguous enough :-) But If you think name will be confusing, I can
change that as suggested.

Thanks,
Santosh

>
>  
>>  #ifdef CONFIG_MODULES
>>  /* For extable.c to search modules' exception tables. */
>> diff --git a/kernel/extable.c b/kernel/extable.c
>> index e23cce6e6092..f6c9406eec7d 100644
>> --- a/kernel/extable.c
>> +++ b/kernel/extable.c
>> @@ -40,13 +40,20 @@ void __init sort_main_extable(void)
>>  	}
>>  }
>>  
>> +/* Given an address, look for it in the kernel exception table */
>> +const
>> +struct exception_table_entry *search_kernel_exception_table(unsigned long addr)
>> +{
>> +	return search_extable(__start___ex_table,
>> +			      __stop___ex_table - __start___ex_table, addr);
>> +}
>> +
>>  /* Given an address, look for it in the exception tables. */
>>  const struct exception_table_entry *search_exception_tables(unsigned long addr)
>>  {
>>  	const struct exception_table_entry *e;
>>  
>> -	e = search_extable(__start___ex_table,
>> -			   __stop___ex_table - __start___ex_table, addr);
>> +	e = search_kernel_exception_table(addr);
>>  	if (!e)
>>  		e = search_module_extables(addr);
>>  	return e;
>> 

-- 
if (( RANDOM % 2 )); then ~/bin/cookie; else fortune -s; fi
#cat ~/notes/quotes | sort -R | head -1 | cut -f2- -d " "

Re: [PATCH v9 7/7] powerpc: add machine check safe copy_to_user

[Balbir Singh]

On 12/8/19 7:22 pm, Santosh Sivaraj wrote:
> Use  memcpy_mcsafe() implementation to define copy_to_user_mcsafe()
> 
> Signed-off-by: Santosh Sivaraj <santosh@fossix.org>
> ---
>  arch/powerpc/Kconfig               |  1 +
>  arch/powerpc/include/asm/uaccess.h | 14 ++++++++++++++
>  2 files changed, 15 insertions(+)
> 
> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> index 77f6ebf97113..4316e36095a2 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -137,6 +137,7 @@ config PPC
>  	select ARCH_HAS_STRICT_KERNEL_RWX	if ((PPC_BOOK3S_64 || PPC32) && !RELOCATABLE && !HIBERNATION)
>  	select ARCH_HAS_TICK_BROADCAST		if GENERIC_CLOCKEVENTS_BROADCAST
>  	select ARCH_HAS_UACCESS_FLUSHCACHE	if PPC64
> +	select ARCH_HAS_UACCESS_MCSAFE		if PPC64
>  	select ARCH_HAS_UBSAN_SANITIZE_ALL
>  	select ARCH_HAVE_NMI_SAFE_CMPXCHG
>  	select ARCH_KEEP_MEMBLOCK
> diff --git a/arch/powerpc/include/asm/uaccess.h b/arch/powerpc/include/asm/uaccess.h
> index 8b03eb44e876..15002b51ff18 100644
> --- a/arch/powerpc/include/asm/uaccess.h
> +++ b/arch/powerpc/include/asm/uaccess.h
> @@ -387,6 +387,20 @@ static inline unsigned long raw_copy_to_user(void __user *to,
>  	return ret;
>  }
>  
> +static __always_inline unsigned long __must_check
> +copy_to_user_mcsafe(void __user *to, const void *from, unsigned long n)
> +{
> +	if (likely(check_copy_size(from, n, true))) {
> +		if (access_ok(to, n)) {
> +			allow_write_to_user(to, n);
> +			n = memcpy_mcsafe((void *)to, from, n);
> +			prevent_write_to_user(to, n);
> +		}
> +	}
> +
> +	return n;

Do we always return n independent of the check_copy_size return value and access_ok return values?

Balbir Singh.

> +}
> +
>  extern unsigned long __clear_user(void __user *addr, unsigned long size);
>  
>  static inline unsigned long clear_user(void __user *addr, unsigned long size)
> 

Re: [PATCH v9 7/7] powerpc: add machine check safe copy_to_user

[Santosh Sivaraj]

Hi Balbir,

Balbir Singh <bsingharora@gmail.com> writes:

> On 12/8/19 7:22 pm, Santosh Sivaraj wrote:
>> Use  memcpy_mcsafe() implementation to define copy_to_user_mcsafe()
>> 
>> Signed-off-by: Santosh Sivaraj <santosh@fossix.org>
>> ---
>>  arch/powerpc/Kconfig               |  1 +
>>  arch/powerpc/include/asm/uaccess.h | 14 ++++++++++++++
>>  2 files changed, 15 insertions(+)
>> 
>> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
>> index 77f6ebf97113..4316e36095a2 100644
>> --- a/arch/powerpc/Kconfig
>> +++ b/arch/powerpc/Kconfig
>> @@ -137,6 +137,7 @@ config PPC
>>  	select ARCH_HAS_STRICT_KERNEL_RWX	if ((PPC_BOOK3S_64 || PPC32) && !RELOCATABLE && !HIBERNATION)
>>  	select ARCH_HAS_TICK_BROADCAST		if GENERIC_CLOCKEVENTS_BROADCAST
>>  	select ARCH_HAS_UACCESS_FLUSHCACHE	if PPC64
>> +	select ARCH_HAS_UACCESS_MCSAFE		if PPC64
>>  	select ARCH_HAS_UBSAN_SANITIZE_ALL
>>  	select ARCH_HAVE_NMI_SAFE_CMPXCHG
>>  	select ARCH_KEEP_MEMBLOCK
>> diff --git a/arch/powerpc/include/asm/uaccess.h b/arch/powerpc/include/asm/uaccess.h
>> index 8b03eb44e876..15002b51ff18 100644
>> --- a/arch/powerpc/include/asm/uaccess.h
>> +++ b/arch/powerpc/include/asm/uaccess.h
>> @@ -387,6 +387,20 @@ static inline unsigned long raw_copy_to_user(void __user *to,
>>  	return ret;
>>  }
>>  
>> +static __always_inline unsigned long __must_check
>> +copy_to_user_mcsafe(void __user *to, const void *from, unsigned long n)
>> +{
>> +	if (likely(check_copy_size(from, n, true))) {
>> +		if (access_ok(to, n)) {
>> +			allow_write_to_user(to, n);
>> +			n = memcpy_mcsafe((void *)to, from, n);
>> +			prevent_write_to_user(to, n);
>> +		}
>> +	}
>> +
>> +	return n;
>
> Do we always return n independent of the check_copy_size return value and
> access_ok return values?

Yes we always return the remaining bytes not copied even if check_copy_size
or access_ok fails.

Santosh

>
> Balbir Singh.
>
>> +}
>> +
>>  extern unsigned long __clear_user(void __user *addr, unsigned long size);
>>  
>>  static inline unsigned long clear_user(void __user *addr, unsigned long size)
>> 

Re: [PATCH v9 6/7] powerpc/mce: Handle UE event for memcpy_mcsafe

[Santosh Sivaraj]

Hi Balbir,

Balbir Singh <bsingharora@gmail.com> writes:

> On 12/8/19 7:22 pm, Santosh Sivaraj wrote:
>> If we take a UE on one of the instructions with a fixup entry, set nip
>> to continue execution at the fixup entry. Stop processing the event
>> further or print it.
>> 
>> Co-developed-by: Reza Arbab <arbab@linux.ibm.com>
>> Signed-off-by: Reza Arbab <arbab@linux.ibm.com>
>> Cc: Mahesh Salgaonkar <mahesh@linux.ibm.com>
>> Signed-off-by: Santosh Sivaraj <santosh@fossix.org>
>> ---
>
> Isn't this based on https://patchwork.ozlabs.org/patch/895294/? If so it
> should still have my author tag and signed-off-by

Originally when I received the series for posting, I had Reza's authorship and
signed-off-by, since the patch changed significantly I added co-developed-by as
Reza. I will update in the next spin.

https://lore.kernel.org/linuxppc-dev/20190702051932.511-1-santosh@fossix.org/

Santosh
>
> Balbir Singh
>
>>  arch/powerpc/include/asm/mce.h  |  4 +++-
>>  arch/powerpc/kernel/mce.c       | 16 ++++++++++++++++
>>  arch/powerpc/kernel/mce_power.c | 15 +++++++++++++--
>>  3 files changed, 32 insertions(+), 3 deletions(-)
>> 
>> diff --git a/arch/powerpc/include/asm/mce.h b/arch/powerpc/include/asm/mce.h
>> index f3a6036b6bc0..e1931c8c2743 100644
>> --- a/arch/powerpc/include/asm/mce.h
>> +++ b/arch/powerpc/include/asm/mce.h
>> @@ -122,7 +122,8 @@ struct machine_check_event {
>>  			enum MCE_UeErrorType ue_error_type:8;
>>  			u8		effective_address_provided;
>>  			u8		physical_address_provided;
>> -			u8		reserved_1[5];
>> +			u8		ignore_event;
>> +			u8		reserved_1[4];
>>  			u64		effective_address;
>>  			u64		physical_address;
>>  			u8		reserved_2[8];
>> @@ -193,6 +194,7 @@ struct mce_error_info {
>>  	enum MCE_Initiator	initiator:8;
>>  	enum MCE_ErrorClass	error_class:8;
>>  	bool			sync_error;
>> +	bool			ignore_event;
>>  };
>>  
>>  #define MAX_MC_EVT	100
>> diff --git a/arch/powerpc/kernel/mce.c b/arch/powerpc/kernel/mce.c
>> index a3b122a685a5..ec4b3e1087be 100644
>> --- a/arch/powerpc/kernel/mce.c
>> +++ b/arch/powerpc/kernel/mce.c
>> @@ -149,6 +149,7 @@ void save_mce_event(struct pt_regs *regs, long handled,
>>  		if (phys_addr != ULONG_MAX) {
>>  			mce->u.ue_error.physical_address_provided = true;
>>  			mce->u.ue_error.physical_address = phys_addr;
>> +			mce->u.ue_error.ignore_event = mce_err->ignore_event;
>>  			machine_check_ue_event(mce);
>>  		}
>>  	}
>> @@ -266,8 +267,17 @@ static void machine_process_ue_event(struct work_struct *work)
>>  		/*
>>  		 * This should probably queued elsewhere, but
>>  		 * oh! well
>> +		 *
>> +		 * Don't report this machine check because the caller has a
>> +		 * asked us to ignore the event, it has a fixup handler which
>> +		 * will do the appropriate error handling and reporting.
>>  		 */
>>  		if (evt->error_type == MCE_ERROR_TYPE_UE) {
>> +			if (evt->u.ue_error.ignore_event) {
>> +				__this_cpu_dec(mce_ue_count);
>> +				continue;
>> +			}
>> +
>>  			if (evt->u.ue_error.physical_address_provided) {
>>  				unsigned long pfn;
>>  
>> @@ -301,6 +311,12 @@ static void machine_check_process_queued_event(struct irq_work *work)
>>  	while (__this_cpu_read(mce_queue_count) > 0) {
>>  		index = __this_cpu_read(mce_queue_count) - 1;
>>  		evt = this_cpu_ptr(&mce_event_queue[index]);
>> +
>> +		if (evt->error_type == MCE_ERROR_TYPE_UE &&
>> +		    evt->u.ue_error.ignore_event) {
>> +			__this_cpu_dec(mce_queue_count);
>> +			continue;
>> +		}
>>  		machine_check_print_event_info(evt, false, false);
>>  		__this_cpu_dec(mce_queue_count);
>>  	}
>> diff --git a/arch/powerpc/kernel/mce_power.c b/arch/powerpc/kernel/mce_power.c
>> index e74816f045f8..1dd87f6f5186 100644
>> --- a/arch/powerpc/kernel/mce_power.c
>> +++ b/arch/powerpc/kernel/mce_power.c
>> @@ -11,6 +11,7 @@
>>  
>>  #include <linux/types.h>
>>  #include <linux/ptrace.h>
>> +#include <linux/extable.h>
>>  #include <asm/mmu.h>
>>  #include <asm/mce.h>
>>  #include <asm/machdep.h>
>> @@ -18,6 +19,7 @@
>>  #include <asm/pte-walk.h>
>>  #include <asm/sstep.h>
>>  #include <asm/exception-64s.h>
>> +#include <asm/extable.h>
>>  
>>  /*
>>   * Convert an address related to an mm to a physical address.
>> @@ -559,9 +561,18 @@ static int mce_handle_derror(struct pt_regs *regs,
>>  	return 0;
>>  }
>>  
>> -static long mce_handle_ue_error(struct pt_regs *regs)
>> +static long mce_handle_ue_error(struct pt_regs *regs,
>> +				struct mce_error_info *mce_err)
>>  {
>>  	long handled = 0;
>> +	const struct exception_table_entry *entry;
>> +
>> +	entry = search_kernel_exception_table(regs->nip);
>> +	if (entry) {
>> +		mce_err->ignore_event = true;
>> +		regs->nip = extable_fixup(entry);
>> +		return 1;
>> +	}
>>  
>>  	/*
>>  	 * On specific SCOM read via MMIO we may get a machine check
>> @@ -594,7 +605,7 @@ static long mce_handle_error(struct pt_regs *regs,
>>  				&phys_addr);
>>  
>>  	if (!handled && mce_err.error_type == MCE_ERROR_TYPE_UE)
>> -		handled = mce_handle_ue_error(regs);
>> +		handled = mce_handle_ue_error(regs, &mce_err);
>>  
>>  	save_mce_event(regs, handled, &mce_err, regs->nip, addr, phys_addr);
>>  
>>