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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org,
        Pedro Miraglia Franco de Carvalho <pedromfc@br.ibm.com>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>
Subject: [PATCH 4.14 023/167] powerpc: Fix DABR match on hash based systems
Date:   Wed, 21 Feb 2018 13:47:14 +0100
Message-Id: <20180221124525.888731903@linuxfoundation.org>
In-Reply-To: <20180221124524.639039577@linuxfoundation.org>
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4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Benjamin Herrenschmidt <benh@kernel.crashing.org>

commit f23ab3efb1b30cc5c5ef5ae4ef294ed467f30675 upstream.

Commit 398a719d34a1 ("powerpc/mm: Update bits used to skip hash_page")
mistakenly dropped the DSISR_DABRMATCH bit from the mask of bit tested
to skip trying to hash a page.

As a result, the DABR matches would no longer be detected.

This adds it back. We open code it in the 2 places where it matters
rather than fold it into DSISR_BAD_FAULT_32S/64S because this isn't
technically a bad fault and while we would never hit it with the
current code, I prefer if page_fault_is_bad() didn't trigger on these.

Fixes: 398a719d34a1 ("powerpc/mm: Update bits used to skip hash_page")
Cc: stable@vger.kernel.org # v4.14
Tested-by: Pedro Miraglia Franco de Carvalho <pedromfc@br.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>


---
 arch/powerpc/kernel/exceptions-64s.S |    2 +-
 arch/powerpc/kernel/head_32.S        |    2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

--- a/arch/powerpc/kernel/exceptions-64s.S
+++ b/arch/powerpc/kernel/exceptions-64s.S
@@ -1617,7 +1617,7 @@ USE_TEXT_SECTION()
 	.balign	IFETCH_ALIGN_BYTES
 do_hash_page:
 	#ifdef CONFIG_PPC_STD_MMU_64
-	lis	r0,DSISR_BAD_FAULT_64S@h
+	lis	r0,(DSISR_BAD_FAULT_64S|DSISR_DABRMATCH)@h
 	ori	r0,r0,DSISR_BAD_FAULT_64S@l
 	and.	r0,r4,r0		/* weird error? */
 	bne-	handle_page_fault	/* if not, try to insert a HPTE */
--- a/arch/powerpc/kernel/head_32.S
+++ b/arch/powerpc/kernel/head_32.S
@@ -388,7 +388,7 @@ DataAccess:
 	EXCEPTION_PROLOG
 	mfspr	r10,SPRN_DSISR
 	stw	r10,_DSISR(r11)
-	andis.	r0,r10,DSISR_BAD_FAULT_32S@h
+	andis.	r0,r10,(DSISR_BAD_FAULT_32S|DSISR_DABRMATCH)@h
 	bne	1f			/* if not, try to put a PTE */
 	mfspr	r4,SPRN_DAR		/* into the hash table */
 	rlwinm	r3,r10,32-15,21,21	/* DSISR_STORE -> _PAGE_RW */