[PATCH kvmtool 0/5] Fix diagnostics and capability probes for protected VMs

[Fuad Tabba <fuad.tabba@linux.dev>]

Hi folks,

These are the kvmtool changes that go with the pKVM series confining a
protected VM's vCPU state to EL2 [1].

That series stops the host reading a protected vCPU's registers once it
has run, and stops it setting the PVTIME attribute. kvmtool dies on
both. Its arm64 register-dump helpers call die() when KVM_GET_ONE_REG
fails, which turns a diagnostic into a VMM abort.
kvm_cpu__setup_pvtime() runs into the new -EPERM and fails vCPU init.

The PVTIME failure is a probe on the wrong fd. kvmtool asks the global
/dev/kvm fd whether steal-time is available, and that fd advertises it
for a protected VM, which cannot use it.
The last patch fixes the same wrong-fd probe for the counter offset,
where "lkvm run --protected --counter-offset" already fails on Linux
7.3-rc1, without the kernel series.
The same conversion went in for the vCPU feature probes in July [2].

Patches 2 and 3 are not specific to protected VMs. They fix the
exit-reason table on the same panic path as patch 1. The lookup ran off
the end of it, and the table had stopped naming anything KVM added after
KVM_EXIT_INTERNAL_ERROR, which on arm64 includes KVM_EXIT_SYSTEM_EVENT
and KVM_EXIT_ARM_NISV.

Patch 1's path needs a protected VM that is already running: "lkvm debug
-d" against one kills the VMM without this series, and prints the errno
with it.

Based on kvmtool master (f67bc0b).

Cheers,
/fuad

[1] https://lore.kernel.org/all/20260831163421.272420-1-fuad.tabba@linux.dev/
[2] https://lore.kernel.org/all/20260714110329.12113-1-fuad.tabba@linux.dev/

Fuad Tabba (5):
  arm64: Do not abort on register-dump failures
  kvm: Bound-check the exit-reason string lookup
  kvm: Name every exit reason the UAPI header defines
  arm64: Query steal-time support on the VM fd
  arm64: Query counter-offset support on the VM fd

 arm64/kvm-cpu.c   | 36 ++++++++++++++++++++++++------------
 arm64/kvm.c       |  2 +-
 arm64/pvtime.c    |  4 ++--
 builtin-run.c     |  2 +-
 include/kvm/kvm.h |  2 +-
 kvm.c             | 37 ++++++++++++++++++++++++++++++++++---
 6 files changed, 63 insertions(+), 20 deletions(-)


base-commit: f67bc0bdae9433a9cfd05e65ea2c1bb6102566d9
-- 
2.39.5