From nobody Mon Nov 25 16:50:16 2024 Received: from fanzine2.igalia.com (fanzine.igalia.com [178.60.130.6]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3FD2C14A0A7; Fri, 25 Oct 2024 16:20:52 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=178.60.130.6 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729873257; cv=none; b=sogqefSqqhhtBOdnlQ52o770MTV+faVDCZ9/xzbGFMI73TDQXv/KhujnxSYLLQZTEYrapCJk0yefSYIjzZtPr8/RACH3aK1wGaTrAdM0721N8Ay1RmPUk2vXu6s68hpiJJbMiTBVDxBBOdopG963Sr9SCR62Id/BWSWzda3d3tw= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729873257; c=relaxed/simple; bh=Nnec9soSG37dMDOLuUy+sWKmAvQakFDh2jmGS5IqsBk=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=VABkDEm4LP+DucirTaLvfMtgLWHXY6tEjuUbjAsrzwgymj+oGXaaJrNx1VF7Y0sgBG+ux0z1JqHwXiiNdG8Lg1ePFaK9Bu1Oshx4EGPJq6tmCZ1O7Ds2G8vqcGzRd3kTAKMeHdlZO4hsWDLH11dJhmgUA6wW7ThbHKLBu3t+pyc= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=igalia.com; spf=pass smtp.mailfrom=igalia.com; dkim=pass (2048-bit key) header.d=igalia.com header.i=@igalia.com header.b=YbG4Yt1f; arc=none smtp.client-ip=178.60.130.6 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=igalia.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=igalia.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=igalia.com header.i=@igalia.com header.b="YbG4Yt1f" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=igalia.com; s=20170329; h=Content-Transfer-Encoding:MIME-Version:Message-ID:Date:Subject: Cc:To:From:Sender:Reply-To:Content-Type:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: In-Reply-To:References:List-Id:List-Help:List-Unsubscribe:List-Subscribe: List-Post:List-Owner:List-Archive; bh=EHLpWcwrtqUoy9yZdOs2vFLOu6EebO+piZZlDeFdZ2U=; b=YbG4Yt1fz5SrBiorVVGTzoxFeJ BhofV7UIxCiw/O7cutk+kz6WvBmC3k7ykYF4pUi6Z41Y6UYNkseVt0/GgfigbyWDEAiyY4Seab18d qoAmreG73WYGcrQoiJnm5C1E5e0fnuHLmy8r/TujFw69CXkl9j8jpFNsDKCRo5EjjK/B9F3WeMKof feMj6hD08D7rHFaMNeGwde8yIbz3T+m0QRWT8e5R/yy3vJTbOjp/mDajPO7WEJJMKc9TPUtvtOBTp 6Ni5Z62vjOyA5HYEFgC4gDu79/x6kDOtLC2DwdWldwyENU8OkTUe+Td1/VEXNbvhdFgi1bqn+J4FG K11pt7BQ==; Received: from [189.79.117.125] (helo=localhost) by fanzine2.igalia.com with esmtpsa (Cipher TLS1.3:ECDHE_SECP256R1__RSA_PSS_RSAE_SHA256__AES_256_GCM:256) (Exim) id 1t4N3P-00F5mK-VM; Fri, 25 Oct 2024 18:20:48 +0200 From: "Guilherme G. Piccoli" To: kexec@lists.infradead.org, linux-doc@vger.kernel.org Cc: bhe@redhat.com, vgoyal@redhat.com, dyoung@redhat.com, corbet@lwn.net, linux-kernel@vger.kernel.org, linux-debuggers@vger.kernel.org, stephen.s.brennan@oracle.com, horms@kernel.org, kernel@gpiccoli.net, kernel-dev@igalia.com, "Guilherme G. Piccoli" Subject: [PATCH V3] Documentation: Improve crash_kexec_post_notifiers description Date: Fri, 25 Oct 2024 13:18:20 -0300 Message-ID: <20241025162042.905104-1-gpiccoli@igalia.com> X-Mailer: git-send-email 2.46.2 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" The crash_kexec_post_notifiers description could be improved a bit, by clarifying its upsides (yes, there are some!) and be more descriptive about the downsides, specially mentioning code that enables the option unconditionally, like Hyper-V[0], PowerPC (fadump)[1] and more recently, AMD SEV[2]. [0] Commit a11589563e96 ("x86/Hyper-V: Report crash register data or kmsg b= efore running crash kernel"). [1] Commit 06e629c25daa ("powerpc/fadump: Fix inaccurate CPU state info in = vmcore generated with panic"). [2] Commit 8ef979584ea8 ("crypto: ccp: Add panic notifier for SEV/SNP firmw= are shutdown on kdump"). Reviewed-by: Stephen Brennan Signed-off-by: Guilherme G. Piccoli --- V3: Improved wording and commit description, detailing more about the addit= ion of code that enables crash_kexec_post_notifiers unconditionally. Thanks Baoquan and Simon for the suggestions! Documentation/admin-guide/kernel-parameters.txt | 16 ++++++++++------ 1 file changed, 10 insertions(+), 6 deletions(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentatio= n/admin-guide/kernel-parameters.txt index 3978fb704c53..2a7a523bb90b 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -918,12 +918,16 @@ the parameter has no effect. =20 crash_kexec_post_notifiers - Run kdump after running panic-notifiers and dumping - kmsg. This only for the users who doubt kdump always - succeeds in any situation. - Note that this also increases risks of kdump failure, - because some panic notifiers can make the crashed - kernel more unstable. + Only jump to kdump kernel after running the panic + notifiers and dumping kmsg. This option increases + the risks of a kdump failure, since some panic + notifiers can make the crashed kernel more unstable. + In configurations where kdump may not be reliable, + running the panic notifiers could allow collecting + more data on dmesg, like stack traces from other CPUS + or extra data dumped by panic_print. Note that some + configurations enable this option unconditionally, + like Hyper-V, PowerPC (fadump) and AMD SEV. =20 crashkernel=3Dsize[KMG][@offset[KMG]] [KNL,EARLY] Using kexec, Linux can switch to a 'crash kernel' --=20 2.46.2