On Mon, Apr 11, 2022 at 04:07:01PM -0400, Jon Kohler wrote:
Move automatic disablement for TSX microcode deprecation from tsx_init() to
x86_get_tsx_auto_mode(), such that systems with tsx=on will continue to
see the TSX CPU features (HLE, RTM) even on updated microcode.
KVM live migration could be possibly be broken in 5.14+ commit 293649307ef9
("x86/tsx: Clear CPUID bits when TSX always force aborts"). Consider the
following scenario:
1. KVM hosts clustered in a live migration capable setup.
2. KVM guests have TSX CPU features HLE and/or RTM presented.
3. One of the three maintenance events occur:
3a. An existing host running kernel >= 5.14 in the pool updated with the
new microcode.
3b. A new host running kernel >= 5.14 is commissioned that already has the
microcode update preloaded.
3c. All hosts are running kernel < 5.14 with microcode update already
loaded and one existing host gets updated to kernel >= 5.14.
4. After maintenance event, the impacted host will not have HLE and RTM
exposed, and live migrations with guests with TSX features might not
migrate.
Which part was this reproduced on? AFAIK server parts(except for some
Intel Xeon E3s) did not get such microcode update.
Thanks,
Pawan
