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Date:   Tue, 12 Dec 2023 19:15:46 -0500
From:   Steven Rostedt <rostedt@goodmis.org>
To:     Alexander Graf <graf@amazon.com>
Cc:     <linux-kernel@vger.kernel.org>,
        <linux-trace-kernel@vger.kernel.org>, <linux-mm@kvack.org>,
        <devicetree@vger.kernel.org>,
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        <x86@kernel.org>, Eric Biederman <ebiederm@xmission.com>,
        "H. Peter Anvin" <hpa@zytor.com>,
        Andy Lutomirski <luto@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        "Rob Herring" <robh+dt@kernel.org>,
        "Andrew Morton" <akpm@linux-foundation.org>,
        Mark Rutland <mark.rutland@arm.com>,
        "Tom Lendacky" <thomas.lendacky@amd.com>,
        Ashish Kalra <ashish.kalra@amd.com>,
        James Gowans <jgowans@amazon.com>,
        Stanislav Kinsburskii <skinsburskii@linux.microsoft.com>,
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        <madvenka@linux.microsoft.com>,
        Anthony Yznaga <anthony.yznaga@oracle.com>,
        Usama Arif <usama.arif@bytedance.com>,
        David Woodhouse <dwmw@amazon.co.uk>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>
Subject: Re: [PATCH 08/15] tracing: Introduce names for ring buffers
Message-ID: <20231212191546.603c0703@gandalf.local.home>
In-Reply-To: <20231213000452.88295-9-graf@amazon.com>
References: <20231213000452.88295-1-graf@amazon.com>
        <20231213000452.88295-9-graf@amazon.com>
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On Wed, 13 Dec 2023 00:04:45 +0000
Alexander Graf <graf@amazon.com> wrote:

> With KHO (Kexec HandOver), we want to preserve trace buffers across
> kexec. To carry over their state between kernels, the kernel needs a
> common handle for them that exists on both sides. As handle we introduce
> names for ring buffers. In a follow-up patch, the kernel can then use
> these names to recover buffer contents for specific ring buffers.
> 

Is there a way to use the trace_array name instead?

The trace_array is the structure that represents each tracing instance. And
it already has a name field. And if you can get the associated ring buffer
from that too.

struct trace_array *tr;

	tr->array_buffer.buffer

	tr->name

When you do: mkdir /sys/kernel/tracing/instance/foo

You create a new trace_array instance where tr->name = "foo" and allocates
the buffer for it as well.

-- Steve