From nobody Mon Nov 25 12:25:44 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 CCE99762E0; Sun, 27 Oct 2024 20:42:10 +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=1730061733; cv=none; b=DXI+wuvermv/qsF8Am++i9AX5K/XRqjwyfyetAAZQSvBg5rK8Q/ZvjB6w+gSdRPZtBhSvo9b7hRXw2Yp2iZknySuy9YW/gWGxP54aKlNlbtnGsXTr65bd06r7pXOPxvQ8KLpgg6CEV3NDRQM/lR87tMehdKsPzuuCQwx/PVteiA= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730061733; c=relaxed/simple; bh=v79S6PUrGE159g3ufeYYr858SvA0k47ESZK2/z2G5ec=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=me61Fv7AkKvVhHhgZ6jjvO9euw4IKcBddnB0OlXgZ1EDrAD79lx0jlE4eBmqD1CHSfVNowGJyiF69aOqH6pRj3ITw+qvjt4vz+M/Q77Us1oTVZ8e2g4xcwybo94flAJGnKh+29ZtG9arhybJg6lgVsSY7O7QfRgMdsWv/cyMAhI= 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=D7TzJVsx; 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="D7TzJVsx" 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=FxIReQk1S15DxmmdigQ/aBi+z2bQeCrpB1btCYSB/wQ=; b=D7TzJVsxo2l8g8syJxk4o1O1sG I8FSJam1xhJuzwqGa5XuazVMdRCj87qWp2kLoUoEpeh/N3r2G/PA0gwf0t91EHRNkUnzFsrmq/Y2+ 5wNQJWWCfInlUzQQot0JDeCyLHXvll3RA3WB+C93fykW3BDsaFgkdK0H8Tcv1FLONeob0z3QzJaJQ owuTzuHsMXzVHiv1cs3KMOjGNskSLKU+BR9dw8e8+9XoUDVmgA7nKQYQm+xk1qhQA7xTgAnZt595x RxMUsTqdLGDj1WMesZ8Zgab3RejU3yqL2H5EYUOdCyW12On5w6u/bUXKsP/6OO37GQeDweIvTtwke MCHXDkZg==; 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 1t5A5N-00Fpx6-MO; Sun, 27 Oct 2024 21:42:06 +0100 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, mhklinux@outlook.com, "Guilherme G. Piccoli" Subject: [PATCH V4] Documentation: Improve crash_kexec_post_notifiers description Date: Sun, 27 Oct 2024 17:36:58 -0300 Message-ID: <20241027204159.985163-1-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-SNP[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 --- V4: * s/AMD SEV/AMD SEV-SNP/ for better clarity, since there are more variants of AMD SEV - thanks a lot Michael Kelley for the good explanation. V3 link, including interesting clarifications about AMD SEV variants, by Michael: https://lore.kernel.org/r/20241025162042.905104-1-gpiccoli@igalia.= com/ 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..1dbd0b0df6fe 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-SNP. =20 crashkernel=3Dsize[KMG][@offset[KMG]] [KNL,EARLY] Using kexec, Linux can switch to a 'crash kernel' --=20 2.46.2