From: "Xu, Yanfei" <yanfei.xu@windriver.com> To: Will Deacon <will@kernel.org> 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: Thu, 3 Jun 2021 18:29:16 +0800 [thread overview] Message-ID: <895953fd-d462-2696-0ab3-72a069ba5a75@windriver.com> (raw) In-Reply-To: <20210602172603.GB31957@willie-the-truck> On 6/3/21 1:26 AM, Will Deacon wrote: > [Please note: This e-mail is from an EXTERNAL e-mail address] > > 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? Ah, Yes! I missed this... Anyway, thanks for your reminding and very sorry for my noise. Regards, Yanfei > > Will >
WARNING: multiple messages have this Message-ID (diff)
From: "Xu, Yanfei" <yanfei.xu@windriver.com> To: Will Deacon <will@kernel.org> 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: Thu, 3 Jun 2021 18:29:16 +0800 [thread overview] Message-ID: <895953fd-d462-2696-0ab3-72a069ba5a75@windriver.com> (raw) In-Reply-To: <20210602172603.GB31957@willie-the-truck> On 6/3/21 1:26 AM, Will Deacon wrote: > [Please note: This e-mail is from an EXTERNAL e-mail address] > > 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? Ah, Yes! I missed this... Anyway, thanks for your reminding and very sorry for my noise. Regards, Yanfei > > Will > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2021-06-03 10:30 UTC|newest] Thread overview: 14+ 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 ` Yanfei Xu 2021-06-01 15:06 ` [PATCH 1/1] " Yanfei Xu 2021-06-01 15:06 ` Yanfei Xu 2021-06-01 17:20 ` Daniel Borkmann 2021-06-01 17:20 ` Daniel Borkmann 2021-06-01 17:41 ` Will Deacon 2021-06-01 17:41 ` Will Deacon 2021-06-02 11:26 ` Xu, Yanfei 2021-06-02 11:26 ` Xu, Yanfei 2021-06-02 17:26 ` Will Deacon 2021-06-02 17:26 ` Will Deacon 2021-06-03 10:29 ` Xu, Yanfei [this message] 2021-06-03 10:29 ` Xu, Yanfei
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