Re: [Qemu-devel] [RFC 6/6] virtio-net: rss: Add bpf filter

[Jason Wang]

On 2018年09月04日 16:14, Daniel P. Berrangé wrote:
> On Tue, Sep 04, 2018 at 11:07:38AM +0800, Jason Wang wrote:
> > On 2018年09月03日 19:54, Daniel P. Berrangé wrote:
> > > > + *
> > > > + * This work is licensed under the terms of the GNU GPL, version 2 or later.
> > > > + * See the COPYING file in the top-level directory.
> > > > + *
> > > > + */
> > > > +
> > > > +#include <linux/bpf.h>
> > > > +
> > > > +#ifndef BPF_RSS_INSNS
> > > > +#define BPF_RSS_INSNS
> > > > +
> > > > +/* bpf_insn array matching l3_l4 section. see tap_bpf_program.c file */
> > > > +struct bpf_insn l3_l4_hash_insns[] = {
> > > > +{0xbf , 0x6 , 0x1 , 0x0000 , 0x00000000},
> > > > +{0x28 , 0x0 , 0x0 , 0x0000 , 0x0000000c},
> > > > +{0xbf , 0x8 , 0x0 , 0x0000 , 0x00000000},
> > > [snip]
> > >
> > > > +};
> > > This massive array is presumably an auto-generated content.
> > >
> > > We shouldn't be storing this in GIT. We need to store the
> > > original preferred source format, and providing makefile
> > > rules to generate it.
> > This is possible. But it depends on eBPF toolchain (e.g recent version of
> > LLVM) to work which is inflexible or impossible to make it work on some
> > distributions. Providing compiled bytecode does not have such limitation.
> Those distros can fix their toolchain if they wish to have the BPF feature
> enabled when building QEMU, just like they would for any other dependancy
> that is needed by QEMU.
>
> Regards,

Well, since bytecode is architecture independent, it needs either 
emulator or JIT to work. So having eBPF toolchain looks unnecessary 
since we're sure it will generate exactly the same bytecodes everywhere. 
I think we can just treat it like some kind of virtio-net firmware and 
ship with bytecodes.

Thanks