netdev - Re: [PATCHv2 RFC net-next] net/vxlan: Fix kernel unaligned access in __vxlan_find

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Date:	Sat, 18 Jul 2015 11:06:26 -0700
From:	Joe Perches <joe@...ches.com>
To:	David Miller <davem@...emloft.net>
Cc:	sowmini.varadhan@...cle.com, netdev@...r.kernel.org,
	alexander.duyck@...il.com
Subject: Re: [PATCHv2 RFC net-next] net/vxlan: Fix kernel unaligned access
 in __vxlan_find_mac

On Fri, 2015-07-17 at 18:18 -0700, David Miller wrote:
> From: Joe Perches <joe@...ches.com> Date: Fri, 17 Jul 2015 16:07:02 -0700
> > On Fri, 2015-07-17 at 22:00 +0200, Sowmini Varadhan wrote:
> >> __vxlan_find_mac invokes ether_addr_equal on the eth_addr field,
> >> which triggers unaligned access messages, so rearrange vxlan_fdb
> >> to avoid this in the most non-intrusive way.

> > What arch does this?

> Sparc, MIPS, etc.

It seems that this code has had unaligned accesses
on this field even before compare_ether_addr was
converted to ether_addr_equal.

Is sparc64 the only one that emits / ratelimits that
unaligned access message?  I looked a little, but I
didn't find a fixup message when MIPS does unaligned
accesses.  Are all the other arches silent when
fixing up unaligned accesses?  Maye adding a generic
debug only ratelimited message might help remove
more of these.  As it's not fatal, naybe the sparc64
message should be KERN_DEBUG/pr_debug.

---

 arch/sparc/kernel/unaligned_64.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/arch/sparc/kernel/unaligned_64.c b/arch/sparc/kernel/unaligned_64.c
index 62098a8..6b7aeb7 100644
--- a/arch/sparc/kernel/unaligned_64.c
+++ b/arch/sparc/kernel/unaligned_64.c
@@ -294,13 +294,9 @@ static void kernel_mna_trap_fault(int fixup_tstate_asi)
 
 static void log_unaligned(struct pt_regs *regs)
 {
-	static DEFINE_RATELIMIT_STATE(ratelimit, 5 * HZ, 5);
+	pr_debug_ratelimited("Kernel unaligned access at TPC[%lx] %pS\n",
+			     regs->tpc, (void *)regs->tpc);
 
-	if (__ratelimit(&ratelimit)) {
-		printk("Kernel unaligned access at TPC[%lx] %pS\n",
-		       regs->tpc, (void *) regs->tpc);
-	}
-}
 
 asmlinkage void kernel_unaligned_trap(struct pt_regs *regs, unsigned int insn)
 {


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