netdev - Re: [PATCH bpf-next 0/3] nfp: bpf: complete shift supports on NFP JIT

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Date:   Fri, 18 May 2018 22:32:39 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Jakub Kicinski <jakub.kicinski@...ronome.com>,
        alexei.starovoitov@...il.com
Cc:     oss-drivers@...ronome.com, netdev@...r.kernel.org
Subject: Re: [PATCH bpf-next 0/3] nfp: bpf: complete shift supports on NFP JIT

On 05/18/2018 09:12 PM, Jakub Kicinski wrote:
> Jiong says:
> 
> NFP eBPF JIT is missing logic indirect shifts (both left and right) and
> arithmetic right shift (both indirect shift and shift by constant).
> 
> This patch adds support for them.
> 
> For indirect shifts, shift amount is not specified as constant, NFP needs
> to get the shift amount through the low 5 bits of source A operand in
> PREV_ALU, therefore extra instructions are needed compared with shifts by
> constants.
> 
> Because NFP is 32-bit, so we are using register pair for 64-bit shifts and
> therefore would need different instruction sequences depending on whether
> shift amount is less than 32 or not.
> 
> NFP branch-on-bit-test instruction emitter is added by this patch set and
> is used for efficient runtime check on shift amount. We'd think the shift
> amount is less than 32 if bit 5 is clear and greater or equal then 32
> otherwise. Shift amount is greater than or equal to 64 will result in
> undefined behavior.
> 
> This patch also use range info to avoid generating unnecessary runtime code
> if we are certain shift amount is less than 32 or not.
> 
> Jiong Wang (3):
>   nfp: bpf: support logic indirect shifts (BPF_[L|R]SH | BPF_X)
>   nfp: bpf: support arithmetic right shift by constant (BPF_ARSH |
>     BPF_K)
>   nfp: bpf: support arithmetic indirect right shift (BPF_ARSH | BPF_X)
> 
>  drivers/net/ethernet/netronome/nfp/bpf/jit.c  | 410 ++++++++++++++++--
>  drivers/net/ethernet/netronome/nfp/bpf/main.h |  28 ++
>  .../net/ethernet/netronome/nfp/bpf/offload.c  |   2 +
>  .../net/ethernet/netronome/nfp/bpf/verifier.c |   8 +
>  drivers/net/ethernet/netronome/nfp/nfp_asm.h  |  18 +-
>  5 files changed, 435 insertions(+), 31 deletions(-)

Applied to bpf-next, thanks guys!