From: Song Liu <song@kernel.org>
To: Mike Rapoport <rppt@kernel.org>
Cc: "Edgecombe, Rick P" <rick.p.edgecombe@intel.com>,
"peterz@infradead.org" <peterz@infradead.org>,
"bpf@vger.kernel.org" <bpf@vger.kernel.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
"hch@lst.de" <hch@lst.de>, "x86@kernel.org" <x86@kernel.org>,
"akpm@linux-foundation.org" <akpm@linux-foundation.org>,
"mcgrof@kernel.org" <mcgrof@kernel.org>,
"Lu, Aaron" <aaron.lu@intel.com>
Subject: Re: [PATCH bpf-next v2 0/5] execmem_alloc for BPF programs
Date: Mon, 14 Nov 2022 12:30:49 -0800 [thread overview]
Message-ID: <CAPhsuW4zKABHC_Stwnkac05Lvww4C_tz-T4JfALDcQusRmsCEw@mail.gmail.com> (raw)
In-Reply-To: <Y3DITs3J8koEw3Hz@kernel.org>
On Sun, Nov 13, 2022 at 2:35 AM Mike Rapoport <rppt@kernel.org> wrote:
>
> On Wed, Nov 09, 2022 at 05:04:25PM +0000, Edgecombe, Rick P wrote:
> > On Wed, 2022-11-09 at 13:17 +0200, Mike Rapoport wrote:
> > > On Tue, Nov 08, 2022 at 04:51:12PM +0000, Edgecombe, Rick P wrote:
> >
> > > How the caching of large pages in vmalloc can be made useful for use
> > > cases like secretmem and PKS?
> >
> > This part is easy I think. If we had an unmapped page allocator it
> > could just feed this.
>
> The unmapped page allocator could be used by anything that needs
> non-default permissions in the direct map and knows how to map the pages
> elsewhere. E.g it would have been a oneliner to switch x86::module_alloc()
> to use unmapped allocations. But ...
>
> > Do you have any idea when you might pick up that stuff again?
>
> ... unfortunately I don't see it happening anytime soon.
>
> > To answer my own question, I think a good first step would be to make
> > the interface also work for non-text_poke() so it could really be cross
> > arch, then use it for everything except modules. The benefit to the
> > other arch's at that point is centralized handling of loading text.
>
> My concern is that the proposed execmem_alloc() cannot be used for
> centralized handling of loading text. I'm not familiar enough with
> modules/ftrace/kprobes/BPF to clearly identify the potential caveats, but
> my gut feeling is that the proposed execmem_alloc() won't be an improvement
> but rather a hindrance for moving to centralized handling of loading text.
I don't follow why this could ever be a hindrance. Luis is very excited about
this, and I am very sure it works for ftrace, kprobe, and BPF.
If there is a better API, it shouldn't be too hard to do the migration. See the
example in 3/5 of the set, where we move x86 BPF jit AND BPF dispatcher
from bpf_prog_pack to execmem_alloc():
5 files changed, 21 insertions(+), 201 deletions(-)
It is not a one liner, but it is definitely very easy.
>
> It feels to me that a lot of ground work is needed to get to the point
> where we can use centralized handling of loading text.
Could you please be more specific on what is needed?
Thanks,
Song
next prev parent reply other threads:[~2022-11-14 20:31 UTC|newest]
Thread overview: 91+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-07 22:39 [PATCH bpf-next v2 0/5] execmem_alloc for BPF programs Song Liu
2022-11-07 22:39 ` [PATCH bpf-next v2 1/5] vmalloc: introduce execmem_alloc, execmem_free, and execmem_fill Song Liu
2022-11-07 22:39 ` [PATCH bpf-next v2 2/5] x86/alternative: support execmem_alloc() and execmem_free() Song Liu
2022-11-07 22:39 ` [PATCH bpf-next v2 3/5] bpf: use execmem_alloc for bpf program and bpf dispatcher Song Liu
2022-11-07 22:39 ` [PATCH bpf-next v2 4/5] vmalloc: introduce register_text_tail_vm() Song Liu
2022-11-07 22:39 ` [PATCH bpf-next v2 5/5] x86: use register_text_tail_vm Song Liu
2022-11-08 19:04 ` Edgecombe, Rick P
2022-11-08 22:15 ` Song Liu
2022-11-15 17:28 ` Edgecombe, Rick P
2022-11-07 22:55 ` [PATCH bpf-next v2 0/5] execmem_alloc for BPF programs Luis Chamberlain
2022-11-07 23:13 ` Song Liu
2022-11-07 23:39 ` Luis Chamberlain
2022-11-08 0:13 ` Edgecombe, Rick P
2022-11-08 2:45 ` Luis Chamberlain
2022-11-08 18:20 ` Song Liu
2022-11-08 18:12 ` Song Liu
2022-11-08 11:27 ` Mike Rapoport
2022-11-08 12:38 ` Aaron Lu
2022-11-09 6:55 ` Christoph Hellwig
2022-11-09 11:05 ` Peter Zijlstra
2022-11-08 16:51 ` Edgecombe, Rick P
2022-11-08 18:50 ` Song Liu
2022-11-09 11:17 ` Mike Rapoport
2022-11-09 17:04 ` Edgecombe, Rick P
2022-11-09 17:53 ` Song Liu
2022-11-13 10:34 ` Mike Rapoport
2022-11-14 20:30 ` Song Liu [this message]
2022-11-15 21:18 ` Luis Chamberlain
2022-11-15 21:39 ` Edgecombe, Rick P
2022-11-16 22:34 ` Luis Chamberlain
2022-11-17 8:50 ` Mike Rapoport
2022-11-17 18:36 ` Song Liu
2022-11-20 10:41 ` Mike Rapoport
2022-11-21 14:52 ` Song Liu
2022-11-30 9:39 ` Mike Rapoport
2022-11-09 17:43 ` Song Liu
2022-11-09 21:23 ` Christophe Leroy
2022-11-10 1:50 ` Song Liu
2022-11-13 10:42 ` Mike Rapoport
2022-11-14 20:45 ` Song Liu
2022-11-15 20:51 ` Luis Chamberlain
2022-11-20 10:44 ` Mike Rapoport
2022-11-08 18:41 ` Song Liu
2022-11-08 19:43 ` Christophe Leroy
2022-11-08 21:40 ` Song Liu
2022-11-13 9:58 ` Mike Rapoport
2022-11-14 20:13 ` Song Liu
2022-11-08 11:44 ` Christophe Leroy
2022-11-08 18:47 ` Song Liu
2022-11-08 19:32 ` Christophe Leroy
2022-11-08 11:48 ` Mike Rapoport
2022-11-15 1:30 ` Song Liu
2022-11-15 17:34 ` Edgecombe, Rick P
2022-11-15 21:54 ` Song Liu
2022-11-15 22:14 ` Edgecombe, Rick P
2022-11-15 22:32 ` Song Liu
2022-11-16 1:20 ` Song Liu
2022-11-16 21:22 ` Edgecombe, Rick P
2022-11-16 22:03 ` Song Liu
2022-11-15 21:09 ` Luis Chamberlain
2022-11-15 21:32 ` Luis Chamberlain
2022-11-15 22:48 ` Song Liu
2022-11-16 22:33 ` Luis Chamberlain
2022-11-16 22:47 ` Edgecombe, Rick P
2022-11-16 23:53 ` Luis Chamberlain
2022-11-17 1:17 ` Song Liu
2022-11-17 9:37 ` Mike Rapoport
2022-11-29 10:23 ` Thomas Gleixner
2022-11-29 17:26 ` Song Liu
2022-11-29 23:56 ` Thomas Gleixner
2022-11-30 16:18 ` Song Liu
2022-12-01 9:08 ` Thomas Gleixner
2022-12-01 19:31 ` Song Liu
2022-12-02 1:38 ` Thomas Gleixner
2022-12-02 8:38 ` Song Liu
2022-12-02 9:22 ` Thomas Gleixner
2022-12-06 20:25 ` Song Liu
2022-12-07 15:36 ` Thomas Gleixner
2022-12-07 16:53 ` Christophe Leroy
2022-12-07 19:29 ` Song Liu
2022-12-07 21:04 ` Thomas Gleixner
2022-12-07 21:48 ` Christophe Leroy
2022-12-07 19:26 ` Song Liu
2022-12-07 20:57 ` Thomas Gleixner
2022-12-07 23:17 ` Song Liu
2022-12-02 10:46 ` Christophe Leroy
2022-12-02 17:43 ` Thomas Gleixner
2022-12-01 20:23 ` Mike Rapoport
2022-12-01 22:34 ` Thomas Gleixner
2022-12-03 14:46 ` Mike Rapoport
2022-12-03 20:58 ` Thomas Gleixner
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