From: Christophe Leroy <christophe.le...@c-s.fr>

commit 415480dce2ef03bb8335deebd2f402f475443ce0 upstream

If a page is already mapped RW without the DIRTY flag, the DIRTY
flag is never set and a TLB store miss exception is taken forever.

This is easily reproduced with the following app:

void main(void)
{
        volatile char *ptr = mmap(0, 4096, PROT_READ | PROT_WRITE, MAP_SHARED | 
MAP_ANONYMOUS, -1, 0);

        *ptr = *ptr;
}

When DIRTY flag is not set, bail out of TLB miss handler and take
a minor page fault which will set the DIRTY flag.

Fixes: f8b58c64eaef ("powerpc/603: let's handle PAGE_DIRTY directly")
Cc: sta...@vger.kernel.org # v5.1+
Reported-by: Doug Crawford <doug.crawf...@intelight-its.com>
Signed-off-by: Christophe Leroy <christophe.le...@c-s.fr>
Signed-off-by: Michael Ellerman <m...@ellerman.id.au>
Link: 
https://lore.kernel.org/r/80432f71194d7ee75b2f5043ecf1501cf1cca1f3.1566196646.git.christophe.le...@c-s.fr
Signed-off-by: He Zhe <zhe...@windriver.com>
---
This is for v5.2/standard/fsl-mpc8315e-rdb. It fixes potential system hang
without any direct warning or error which has not been observed on qemuppc.

It has not been ported to stable tree.

 arch/powerpc/kernel/head_32.S | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/kernel/head_32.S b/arch/powerpc/kernel/head_32.S
index f255e22..534dd27 100644
--- a/arch/powerpc/kernel/head_32.S
+++ b/arch/powerpc/kernel/head_32.S
@@ -557,9 +557,9 @@ DataStoreTLBMiss:
        cmplw   0,r1,r3
        mfspr   r2, SPRN_SPRG_PGDIR
 #ifdef CONFIG_SWAP
-       li      r1, _PAGE_RW | _PAGE_PRESENT | _PAGE_ACCESSED
+       li      r1, _PAGE_RW | _PAGE_DIRTY | _PAGE_PRESENT | _PAGE_ACCESSED
 #else
-       li      r1, _PAGE_RW | _PAGE_PRESENT
+       li      r1, _PAGE_RW | _PAGE_DIRTY | _PAGE_PRESENT
 #endif
        bge-    112f
        lis     r2, (swapper_pg_dir - PAGE_OFFSET)@ha   /* if kernel address, 
use */
-- 
2.7.4

-- 
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