netdev - Re: [PATCH 1/1] bpf: avoid unnecessary IPI in bpf_flush

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Message-ID: <20210601174114.GA29130@willie-the-truck>
Date:   Tue, 1 Jun 2021 18:41:15 +0100
From:   Will Deacon <will@...nel.org>
To:     Daniel Borkmann <daniel@...earbox.net>
Cc:     Yanfei Xu <yanfei.xu@...driver.com>, ast@...nel.org,
        zlim.lnx@...il.com, catalin.marinas@....com, andrii@...nel.org,
        kafai@...com, songliubraving@...com, yhs@...com,
        john.fastabend@...il.com, kpsingh@...nel.org,
        netdev@...r.kernel.org, bpf@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] bpf: avoid unnecessary IPI in bpf_flush_icache

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.

Will