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Peter Anvin" , virtualization@lists.linux.dev, bcm-kernel-feedback-list@broadcom.com, linux-kernel@vger.kernel.org, John Ogness , Steven Rostedt , Sergey Senozhatsky , Kees Cook , Jonathan Corbet , Bo Gan , Brennan Lamoreaux , kexec@lists.infradead.org, linux-doc@vger.kernel.org, "Guilherme G. Piccoli" , Maaz Mombasawala , Shuah Khan , Randy Dunlap , Stephen Brennan , Michael Kelley , Ian Forbes Subject: [PATCH v2 5/6] x86/vmware: Add the vmware_record_panic_msg sysctl Date: Mon, 28 Sep 2026 13:55:39 -0400 Message-ID: <269888613b5dc16d19899b2c87c5ecdfd2610e8d.1790014793.git.zack.rusin@broadcom.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-DetectorID-Processed: b00c1d49-9d2e-4205-b15f-d015386d3d5e Allow administrators to disable host log transfer on ordinary guests or opt in on encrypted guests. Expose the boolean recording policy through kernel.vmware_record_panic_msg using proc_dobool(), as Joel suggested. Zero disables recording, nonzero integers enable it, and reads return 0 or 1. Register the sysctl only after the logger is ready. A registration failure leaves the internal default in force. Document that disabling the old post-notifier ordering does not disable this independent logger. Link: https://lore.kernel.org/r/4e73yd2ofpdzl6rptzvd74no3hnyfblknoq7wzxlw7f3zjbz7c@srfabx6lsusj Signed-off-by: Zack Rusin --- v2: use bool/proc_dobool as Joel requested; document direct crash entry. Maaz's v1 Reviewed-by is omitted for renewed review of the changed sysctl. Documentation/admin-guide/sysctl/kernel.rst | 20 ++++++++++++++++++++ arch/x86/kernel/cpu/vmware.c | 15 +++++++++++++++ 2 files changed, 35 insertions(+) diff --git a/Documentation/admin-guide/sysctl/kernel.rst b/Documentation/admin-guide/sysctl/kernel.rst index ffea61d448eb..be13c143b8bb 100644 --- a/Documentation/admin-guide/sysctl/kernel.rst +++ b/Documentation/admin-guide/sysctl/kernel.rst @@ -1690,6 +1690,26 @@ entry will default to 2 instead of 0. = ============================================================= +vmware_record_panic_msg +====================== + +Controls whether panic or fatal-oops kmsg data is written to the host's +``vmware.log`` before kdump. This setting does not control the separate +VMware guest-crash event. Writing zero disables recording; writing a +nonzero integer enables it. Reads return 0 or 1. + += ============================================================== +0 Do not write kmsg data to ``vmware.log``. This is the default + for encrypted guests. +1 Write kmsg data to ``vmware.log``. This is the default for + ordinary guests. += ============================================================== + +``crash_kexec_post_notifiers=0`` alone does not disable this logger. +``panic_pre_kdump_postpone=1`` skips early logging but leaves late panic +logging eligible; set this sysctl to 0 to disable both. + + warn_limit ========== diff --git a/arch/x86/kernel/cpu/vmware.c b/arch/x86/kernel/cpu/vmware.c index ccf8dc84b30e..4b0e5b084c2c 100644 --- a/arch/x86/kernel/cpu/vmware.c +++ b/arch/x86/kernel/cpu/vmware.c @@ -33,6 +33,7 @@ #include #include #include +#include #include #include #include @@ -260,6 +261,16 @@ static int vmware_log_rpc(const char *buffer, size_t length) static struct page *vmware_panic_page; static bool vmware_record_panic_msg; +static const struct ctl_table vmware_panic_sysctls[] = { + { + .procname = "vmware_record_panic_msg", + .data = &vmware_record_panic_msg, + .maxlen = sizeof(vmware_record_panic_msg), + .mode = 0644, + .proc_handler = proc_dobool, + }, +}; + static int vmware_panic_log_notify(struct notifier_block *nb, unsigned long action, void *data) { @@ -311,6 +322,10 @@ static int __init vmware_panic_log_init(void) vmware_panic_page = NULL; } + if (vmware_panic_page && IS_ENABLED(CONFIG_SYSCTL) && + !register_sysctl("kernel", vmware_panic_sysctls)) + pr_err("failed to register panic log sysctl\n"); + return 0; } early_initcall(vmware_panic_log_init);