From mboxrd@z Thu Jan  1 00:00:00 1970
From: Alexei Starovoitov <ast@plumgrid.com>
Subject: Re: [PATCH net-next 5/5] s390/bpf: recache skb->data/hlen for
 skb_vlan_push/pop
Date: Tue, 28 Jul 2015 10:19:28 -0700
Message-ID: <55B7B9A0.5060606@plumgrid.com>
References: <1438092600-16221-1-git-send-email-holzheu@linux.vnet.ibm.com>
 <1438092600-16221-6-git-send-email-holzheu@linux.vnet.ibm.com>
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Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>,
	Daniel Borkmann <daniel@iogearbox.net>, netdev@vger.kernel.org,
	linux-s390@vger.kernel.org
To: Michael Holzheu <holzheu@linux.vnet.ibm.com>,
	David Miller <davem@davemloft.net>
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On 7/28/15 7:10 AM, Michael Holzheu wrote:
> Allow eBPF programs attached to TC qdiscs call skb_vlan_push/pop
> via helper functions. These functions may change skb->data/hlen.
> This data is cached by s390 JIT to improve performance of ld_abs/ld_ind
> instructions. Therefore after a change we have to reload the data.
>
> In case of usage of skb_vlan_push/pop, in the prologue we store
> the SKB pointer on the stack and restore it after BPF_JMP_CALL
> to skb_vlan_push/pop.
>
> Signed-off-by: Michael Holzheu<holzheu@linux.vnet.ibm.com>

Thanks!
Acked-by: Alexei Starovoitov <ast@plumgrid.com>