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From: Vasily Gorbik <gor@linux.ibm.com>
To: Ilya Leoshkevich <iii@linux.ibm.com>
Cc: Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Andrii Nakryiko <andrii@kernel.org>,
	bpf@vger.kernel.org, Heiko Carstens <hca@linux.ibm.com>,
	Alexander Gordeev <agordeev@linux.ibm.com>
Subject: Re: [PATCH 0/2] bpf/s390: Implement get_preempt_count()
Date: Tue, 17 Feb 2026 18:55:33 +0100	[thread overview]
Message-ID: <your-ad-here.call-01771350933-ext-9929@work.hours> (raw)
In-Reply-To: <20260217160813.100855-1-iii@linux.ibm.com>

On Tue, Feb 17, 2026 at 05:05:07PM +0100, Ilya Leoshkevich wrote:
> Hi,
> 
> This series adds get_preempt_count() BPF implementation for s390.
> On s390 preempt_count lives in lowcore: a per-cpu data structure
> mapped at virtual address 0 or 0x70000 depending on the kernel
> command line.
> 
> Patch 1 adds a kfunc to obtain lowcore address.
> Patch 2 is the implementation that delegates to it.

Hi Ilya,

do we really want to expose bpf_get_lowcore() (full lowcore) to BPF just
to implement get_preempt_count()?

Could we instead provide a narrow kfunc/helper that returns preempt_count
and keep lowcore details internal?

Thanks

  parent reply	other threads:[~2026-02-17 17:55 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-02-17 16:05 [PATCH 0/2] bpf/s390: Implement get_preempt_count() Ilya Leoshkevich
2026-02-17 16:05 ` [PATCH 1/2] s390: Introduce bpf_get_lowcore() kfunc Ilya Leoshkevich
2026-02-17 16:05 ` [PATCH 2/2] bpf/s390: Implement get_preempt_count() Ilya Leoshkevich
2026-02-17 17:55 ` Vasily Gorbik [this message]
2026-02-17 19:32   ` [PATCH 0/2] " Alexei Starovoitov
2026-02-17 23:34     ` Ilya Leoshkevich
2026-02-18  0:18       ` Alexei Starovoitov
2026-03-03 16:40 ` patchwork-bot+netdevbpf

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