[PATCH v3] mips: scache: fix scache init with invalid line size.

[PATCH v3] mips: scache: fix scache init with invalid line size.

[Govindraj Raja]

In current scache init cache line_size is determined from
cpu config register, however if there there no scache
then mips_sc_probe_cm3 function populates a invalid line_size of 2.

The invalid line_size can cause a NULL pointer deference
during r4k_dma_cache_inv as r4k_blast_scache is populated
based on line_size. Scache line_size of 2 is invalid option in
r4k_blast_scache_setup.

This issue was faced during a MIPS I6400 based virtual platform bring up
where scache was not available in virtual platform model.

Changes from v2:
	https://patchwork.linux-mips.org/patch/12243/
	Fix return value, ensure function returns true only if
	scache is identified.

Changes from v1:
	https://patchwork.linux-mips.org/patch/12126/
	Avoid clearing of MIPS_CACHE_NOT_PRESENT if scache is absent

Fixes: 7d53e9c4cd21("MIPS: CM3: Add support for CM3 L2 cache.")
Cc: <stable@vger.kernel.org> # v4.2+
Cc: Paul Burton <paul.burton@imgtec.com>
Cc: James Hogan <james.hogan@imgtec.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: James Hartley <James.Hartley@imgtec.com>
Cc: linux-mips@linux-mips.org
Signed-off-by: Govindraj Raja <Govindraj.Raja@imgtec.com>
---
 arch/mips/mm/sc-mips.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/arch/mips/mm/sc-mips.c b/arch/mips/mm/sc-mips.c
index 2496475..91dec32 100644
--- a/arch/mips/mm/sc-mips.c
+++ b/arch/mips/mm/sc-mips.c
@@ -164,11 +164,13 @@ static int __init mips_sc_probe_cm3(void)
 
 	sets = cfg & CM_GCR_L2_CONFIG_SET_SIZE_MSK;
 	sets >>= CM_GCR_L2_CONFIG_SET_SIZE_SHF;
-	c->scache.sets = 64 << sets;
+	if (sets)
+		c->scache.sets = 64 << sets;
 
 	line_sz = cfg & CM_GCR_L2_CONFIG_LINE_SIZE_MSK;
 	line_sz >>= CM_GCR_L2_CONFIG_LINE_SIZE_SHF;
-	c->scache.linesz = 2 << line_sz;
+	if (line_sz)
+		c->scache.linesz = 2 << line_sz;
 
 	assoc = cfg & CM_GCR_L2_CONFIG_ASSOC_MSK;
 	assoc >>= CM_GCR_L2_CONFIG_ASSOC_SHF;
@@ -176,9 +178,12 @@ static int __init mips_sc_probe_cm3(void)
 	c->scache.waysize = c->scache.sets * c->scache.linesz;
 	c->scache.waybit = __ffs(c->scache.waysize);
 
-	c->scache.flags &= ~MIPS_CACHE_NOT_PRESENT;
+	if (c->scache.linesz) {
+		c->scache.flags &= ~MIPS_CACHE_NOT_PRESENT;
+		return 1;
+	}
 
-	return 1;
+	return 0;
 }
 
 static inline int __init mips_sc_probe(void)
-- 
2.5.0

Re: [PATCH v3] mips: scache: fix scache init with invalid line size.

[Ralf Baechle]

On Mon, Feb 29, 2016 at 11:41:20AM +0000, Govindraj Raja wrote:

> Cc: <stable@vger.kernel.org> # v4.2+

You meant 4.3+; 4.2 doesn't have a mips_sc_probe_cm3 function.  Other
than that, ok & applied.

  Ralf

Re: [PATCH v3] mips: scache: fix scache init with invalid line size.

[Govindraj Raja]

On 29/02/16 14:47, Ralf Baechle wrote:
> On Mon, Feb 29, 2016 at 11:41:20AM +0000, Govindraj Raja wrote:
>
>> Cc: <stable@vger.kernel.org> # v4.2+
> You meant 4.3+; 4.2 doesn't have a mips_sc_probe_cm3 function.  Other
> than that, ok & applied.
>

Yes it was supposed to be 4.3+

thanks

--
Thanks,
Govindraj.R