From: Will Deacon <will@kernel.org>
To: "Xu, Yanfei" <yanfei.xu@windriver.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>,
ast@kernel.org, zlim.lnx@gmail.com, catalin.marinas@arm.com,
andrii@kernel.org, kafai@fb.com, songliubraving@fb.com,
yhs@fb.com, john.fastabend@gmail.com, kpsingh@kernel.org,
netdev@vger.kernel.org, bpf@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/1] bpf: avoid unnecessary IPI in bpf_flush_icache
Date: Wed, 2 Jun 2021 18:26:04 +0100 [thread overview]
Message-ID: <20210602172603.GB31957@willie-the-truck> (raw)
In-Reply-To: <7637dcdf-12b4-2861-3c76-f8a8e240a05e@windriver.com>
On Wed, Jun 02, 2021 at 07:26:03PM +0800, Xu, Yanfei wrote:
>
>
> On 6/2/21 1:41 AM, Will Deacon wrote:
> > [Please note: This e-mail is from an EXTERNAL e-mail address]
> >
> > On Tue, Jun 01, 2021 at 07:20:04PM +0200, Daniel Borkmann wrote:
> > > On 6/1/21 5:06 PM, Yanfei Xu wrote:
> > > > It's no need to trigger IPI for keeping pipeline fresh in bpf case.
> > >
> > > This needs a more concrete explanation/analysis on "why it is safe" to do so
> > > rather than just saying that it is not needed.
> >
> > Agreed. You need to show how the executing thread ends up going through a
> > context synchronizing operation before jumping to the generated code if
> > the IPI here is removed.
>
> This patch came out with I looked through ftrace codes. Ftrace modify
> the text code and don't send IPI in aarch64_insn_patch_text_nosync(). I
> mistakenly thought the bpf is same with ftrace.
>
> But now I'm still not sure why the ftrace don't need the IPI to go
> through context synchronizing, maybe the worst situation is omit a
> tracing event?
I think ftrace handles this itself via ftrace_sync_ipi, no?
Will
next prev parent reply other threads:[~2021-06-02 17:26 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-01 15:06 [PATCH 0/1] bpf: avoid unnecessary IPI in bpf_flush_icache Yanfei Xu
2021-06-01 15:06 ` [PATCH 1/1] " Yanfei Xu
2021-06-01 17:20 ` Daniel Borkmann
2021-06-01 17:41 ` Will Deacon
2021-06-02 11:26 ` Xu, Yanfei
2021-06-02 17:26 ` Will Deacon [this message]
2021-06-03 10:29 ` Xu, Yanfei
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