On Fri, Sep 28, 2012 at 02:02:46AM +0100, Simon Horman wrote:

On Fri, Sep 21, 2012 at 10:00:37AM +0900, Simon Horman wrote:

quoted

On Thu, Sep 20, 2012 at 10:35:50AM +0100, Catalin Marinas wrote:

quoted

On 13 September 2012 02:00, Simon Horman [off-list ref] wrote:

quoted

On Wed, Sep 12, 2012 at 10:59:35AM -0700, Stephen Boyd wrote:

quoted

On 09/12/12 00:14, Simon Horman wrote:

quoted

@@ -1423,6 +1423,15 @@ config ARM_ERRATA_775420
          deadlock. This workaround puts DSB before executing ISB at the
          beginning of the abort exception handler.

+config ARM_ERRATA_782773
+   bool "ARM errata: Updating a translation entry might cause an unexpected translation fault"
+   depends on CPU_V7
+   help
+     This option enables the workaround for the 782773 Cortex-A9 (all r0,
+     ,r2 and r3 revisions) erratum. It might cause MMU exception in case

Seems to be an extra comma here.

Thanks, here is an updated version.

From: Kouei Abe <redacted>

arm: Add ARM ERRATA 782773 workaround

Signed-off-by: Kouei Abe <redacted>
Signed-off-by: Simon Horman <horms@verge.net.au>

I would add some text to the commit log as well, even though it
matches the Kconfig entry.

Sure, an updated patch is below.
I also reworded the text to make it easier on my eyes,
I don't think the meaning has been altered.

quoted

Have you hit this in practice? In general the kernel shouldn't access
kernel virtual address corresponding to a page table that is being
changed. For user address space it is possible but the kernel can
handle use translation faults, even though they may be spurious.

I believe that Abe-san's team have come up against this,
I can confirm that if it is important.

I was wondering if I could get an Ack on this as you indicated
in another email that you feel that the implementation is an
appropriate workaround.

I'd like to know whether this is actually hit in practice and the
conditions. The only time when we write live (i.e. translation that's
currently in use) kernel mappings is during boot, alloc_init_section()
replacing (though with the same value) the initial memory map. But if
that's the scenario you are getting, I would rather add another
flush_pmd_entry() call before setting the pmd in alloc_init_section().

I'm not convinced a costly run-time workaround in set_pte is needed.

-- 
Catalin