linux-kernel - Re: [PATCH v6 bpf-next 0/5] bpf_prog

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Message-ID: <YshUEEQ0lk1ON7H6@bombadil.infradead.org>
Date:   Fri, 8 Jul 2022 08:58:08 -0700
From:   Luis Chamberlain <mcgrof@...nel.org>
To:     Song Liu <songliubraving@...com>
Cc:     Song Liu <song@...nel.org>, bpf <bpf@...r.kernel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Linux-MM <linux-mm@...ck.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Kernel Team <Kernel-team@...com>,
        "x86@...nel.org" <x86@...nel.org>,
        "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
        "rick.p.edgecombe@...el.com" <rick.p.edgecombe@...el.com>
Subject: Re: [PATCH v6 bpf-next 0/5] bpf_prog_pack followup

On Fri, Jul 08, 2022 at 01:36:25AM +0000, Song Liu wrote:
> 
> 
> > On Jul 7, 2022, at 5:53 PM, Luis Chamberlain <mcgrof@...nel.org> wrote:
> > 
> > On Thu, Jul 07, 2022 at 11:52:58PM +0000, Song Liu wrote:
> >>> On Jul 7, 2022, at 3:59 PM, Luis Chamberlain <mcgrof@...nel.org> wrote:
> >>> 
> >>> On Thu, Jul 07, 2022 at 03:35:41PM -0700, Song Liu wrote:
> >>>> This set is the second half of v4 [1].
> >>>> 
> >>>> Changes v5 => v6:
> >>>> 1. Rebase and extend CC list.
> >>> 
> >>> Why post a new iteration so soon without completing the discussion we
> >>> had? It seems like we were at least going somewhere. If it's just
> >>> to include mm as I requested, sure, that's fine, but this does not
> >>> provide context as to what we last were talking about.
> >> 
> >> Sorry for sending v6 too soon. The primary reason was to extend the CC
> >> list and add it back to patchwork (v5 somehow got archived). 
> >> 
> >> Also, I think vmalloc_exec_ work would be a separate project, while this 
> >> set is the followup work of bpf_prog_pack. Does this make sense? 
> >> 
> >> Btw, vmalloc_exec_ work could be a good topic for LPC. It will be much
> >> more efficient to discuss this in person. 
> > 
> > What we need is input from mm / arch folks. What is not done here is
> > what that stuff we're talking about is and so mm folks can't guess. My
> > preference is to address that.
> > 
> > I don't think in person discussion is needed if the only folks
> > discussing this topic so far is just you and me.
> 
> How about we start a thread with mm / arch folks for the vmalloc_exec_*
> topic? I will summarize previous discussions and include pointers to 
> these discussions. If necessary, we can continue the discussion at LPC.

This sounds like a nice thread to use as this is why we are talking
about that topic.

> OTOH, I guess the outcome of that discussion should not change this set? 

If the above is done right then actually I think it would show similar
considerations for a respective free for module_alloc_huge().

> If we have concern about module_alloc_huge(), maybe we can have bpf code 
> call vmalloc directly (until we have vmalloc_exec_)? 

You'd need to then still open code in a similar way the same things
which we are trying to reach consensus on.

> What do you think about this plan?

I think we should strive to not be lazy and sloppy, and prevent growth
of sloppy code. So long as we do that I think this is all reasoanble.

  Luis