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Message-ID: <CAPhsuW5SL4_=ZXdHZV8o0KS+5Vf25UMvEKhRgFQLioFtf2pgoQ@mail.gmail.com>
Date: Thu, 18 Apr 2024 14:01:22 -0700
From: Song Liu <song@...nel.org>
To: Mike Rapoport <rppt@...nel.org>
Cc: Mark Rutland <mark.rutland@....com>, Peter Zijlstra <peterz@...radead.org>,
linux-kernel@...r.kernel.org, Alexandre Ghiti <alexghiti@...osinc.com>,
Andrew Morton <akpm@...ux-foundation.org>, Bjorn Topel <bjorn@...nel.org>,
Catalin Marinas <catalin.marinas@....com>, Christophe Leroy <christophe.leroy@...roup.eu>,
"David S. Miller" <davem@...emloft.net>, Dinh Nguyen <dinguyen@...nel.org>,
Donald Dutile <ddutile@...hat.com>, Eric Chanudet <echanude@...hat.com>,
Heiko Carstens <hca@...ux.ibm.com>, Helge Deller <deller@....de>, Huacai Chen <chenhuacai@...nel.org>,
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Michael Ellerman <mpe@...erman.id.au>, Nadav Amit <nadav.amit@...il.com>,
Palmer Dabbelt <palmer@...belt.com>, Puranjay Mohan <puranjay12@...il.com>,
Rick Edgecombe <rick.p.edgecombe@...el.com>, Russell King <linux@...linux.org.uk>,
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Thomas Gleixner <tglx@...utronix.de>, Will Deacon <will@...nel.org>, bpf@...r.kernel.org,
linux-arch@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
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Subject: Re: [PATCH v4 05/15] mm: introduce execmem_alloc() and execmem_free()
On Thu, Apr 18, 2024 at 10:54 AM Mike Rapoport <rppt@...nel.org> wrote:
>
> On Thu, Apr 18, 2024 at 09:13:27AM -0700, Song Liu wrote:
> > On Thu, Apr 18, 2024 at 8:37 AM Mike Rapoport <rppt@...nel.org> wrote:
> > > > >
> > > > > I'm looking at execmem_types more as definition of the consumers, maybe I
> > > > > should have named the enum execmem_consumer at the first place.
> > > >
> > > > I think looking at execmem_type from consumers' point of view adds
> > > > unnecessary complexity. IIUC, for most (if not all) archs, ftrace, kprobe,
> > > > and bpf (and maybe also module text) all have the same requirements.
> > > > Did I miss something?
> > >
> > > It's enough to have one architecture with different constrains for kprobes
> > > and bpf to warrant a type for each.
> >
> > AFAICT, some of these constraints can be changed without too much work.
>
> But why?
> I honestly don't understand what are you trying to optimize here. A few
> lines of initialization in execmem_info?
IIUC, having separate EXECMEM_BPF and EXECMEM_KPROBE makes it
harder for bpf and kprobe to share the same ROX page. In many use cases,
a 2MiB page (assuming x86_64) is enough for all BPF, kprobe, ftrace, and
module text. It is not efficient if we have to allocate separate pages for each
of these use cases. If this is not a problem, the current approach works.
Thanks,
Song
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