[PATCH v1 0/4] x86/vmware: Preserve panic diagnostics in vmware.log

[Zack Rusin <zack.rusin@broadcom.com>]

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/20260309235250.2611115-1-alexey.makhalov@broadcom.com/

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