netdev - Re: [PATCH net-next 5/5] s390/bpf: recache skb->data/hlen for skb_vlan

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Message-ID: <55B7B9A0.5060606@plumgrid.com>
Date:	Tue, 28 Jul 2015 10:19:28 -0700
From:	Alexei Starovoitov <ast@...mgrid.com>
To:	Michael Holzheu <holzheu@...ux.vnet.ibm.com>,
	David Miller <davem@...emloft.net>
Cc:	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Daniel Borkmann <daniel@...earbox.net>, netdev@...r.kernel.org,
	linux-s390@...r.kernel.org
Subject: Re: [PATCH net-next 5/5] s390/bpf: recache skb->data/hlen for
 skb_vlan_push/pop

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@...ux.vnet.ibm.com>

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

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