Patch "powerpc/powernv: Fix kexec crashes caused by tlbie tracing" has been added to the 4.14-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    powerpc/powernv: Fix kexec crashes caused by tlbie tracing

to the 4.14-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     powerpc-powernv-fix-kexec-crashes-caused-by-tlbie-tracing.patch
and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From a3961f824cdbe7eb431254dc7d8f6f6767f474aa Mon Sep 17 00:00:00 2001
From: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
Date: Wed, 22 Nov 2017 23:02:07 +0530
Subject: powerpc/powernv: Fix kexec crashes caused by tlbie tracing

From: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>

commit a3961f824cdbe7eb431254dc7d8f6f6767f474aa upstream.

Rebooting into a new kernel with kexec fails in trace_tlbie() which is
called from native_hpte_clear(). This happens if the running kernel
has CONFIG_LOCKDEP enabled. With lockdep enabled, the tracepoints
always execute few RCU checks regardless of whether tracing is on or
off. We are already in the last phase of kexec sequence in real mode
with HILE_BE set. At this point the RCU check ends up in
RCU_LOCKDEP_WARN and causes kexec to fail.

Fix this by not calling trace_tlbie() from native_hpte_clear().

mpe: It's not safe to call trace points at this point in the kexec
path, even if we could avoid the RCU checks/warnings. The only
solution is to not call them.

Fixes: 0428491cba92 ("powerpc/mm: Trace tlbie(l) instructions")
Signed-off-by: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
Reported-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Suggested-by: Michael Ellerman <mpe@ellerman.id.au>
Acked-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/powerpc/mm/hash_native_64.c |   15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

--- a/arch/powerpc/mm/hash_native_64.c
+++ b/arch/powerpc/mm/hash_native_64.c
@@ -47,7 +47,8 @@
 
 DEFINE_RAW_SPINLOCK(native_tlbie_lock);
 
-static inline void __tlbie(unsigned long vpn, int psize, int apsize, int ssize)
+static inline unsigned long  ___tlbie(unsigned long vpn, int psize,
+						int apsize, int ssize)
 {
 	unsigned long va;
 	unsigned int penc;
@@ -100,7 +101,15 @@ static inline void __tlbie(unsigned long
 			     : "memory");
 		break;
 	}
-	trace_tlbie(0, 0, va, 0, 0, 0, 0);
+	return va;
+}
+
+static inline void __tlbie(unsigned long vpn, int psize, int apsize, int ssize)
+{
+	unsigned long rb;
+
+	rb = ___tlbie(vpn, psize, apsize, ssize);
+	trace_tlbie(0, 0, rb, 0, 0, 0, 0);
 }
 
 static inline void __tlbiel(unsigned long vpn, int psize, int apsize, int ssize)
@@ -652,7 +661,7 @@ static void native_hpte_clear(void)
 		if (hpte_v & HPTE_V_VALID) {
 			hpte_decode(hptep, slot, &psize, &apsize, &ssize, &vpn);
 			hptep->v = 0;
-			__tlbie(vpn, psize, apsize, ssize);
+			___tlbie(vpn, psize, apsize, ssize);
 		}
 	}
 


Patches currently in stable-queue which might be from mahesh@linux.vnet.ibm.com are

queue-4.14/powerpc-powernv-fix-kexec-crashes-caused-by-tlbie-tracing.patch