A virtual machine may have neither guest-local persistent storage nor working userspace after a panic. The host's vmware.log remains available after the VM terminates, and a production encrypted guest is the only component able to export readable panic text. Hyper-V already provides this class of host-persistent panic reporting.
Add a panic-only VMware logger that copies the newest 4 KiB of the kernel log and sends it with bounded low-bandwidth RPC work. Ordinary guests enable text transfer by default; encrypted guests require an administrator to opt in through kernel.vmware_record_panic_msg. A separate late dumper reports the structured crash event after built-in dumpers and suppresses the event while a crash kernel is loaded, because a configured VMware host may terminate the VM before the reporting hypercall returns. Patch 4 makes panic diagnostics run before kdump by default on VMware guests. This follows existing platform uses of crash_kexec_post_notifiers, with Hyper-V as the closest guest-reporting precedent. Unlike Hyper-V, VMware exposes no capability bit for this behavior. An explicit crash_kexec_post_notifiers=0 still wins, and patch 4 can be dropped without affecting patches 1 through 3. This replaces patches 2 and 3 of Alexey's v2 posting: https://lore.kernel.org/all/[email protected]/ The intended merge path is tip's x86/vmware branch. Boris please review the VMware transport and policy. Petr and John, please review the panic-only dumper use and registration ordering. Joel and Kees, please review the sysctl. Baoquan and the KEXEC/KDUMP team, please review the loaded-crash-kernel guard and the default in patch 4. Zack Rusin (4): x86/vmware: Add a bounded panic log sender x86/vmware: Add the vmware_record_panic_msg sysctl x86/vmware: Report guest crashes after kmsg dumpers x86/vmware: Run panic diagnostics before kdump by default Documentation/admin-guide/sysctl/kernel.rst | 14 ++ arch/x86/include/asm/vmware.h | 2 + arch/x86/kernel/cpu/vmware.c | 245 ++++++++++++++++++++ 3 files changed, 261 insertions(+) base-commit: cee9395acd8043be0644b25c34bfa86623f2b935 -- 2.53.0
