[PATCH 0/1] x86/split_lock: check split lock feature on initialization

[Benjamin Lamowski]

Hi,

During regression testing of our hypervisor[1] with the current git tip,
we got writes to the TEST_CTRL MSR on hardware that does not support
split lock detection. While the original split_lock implementation does
not exhibit this behavior, the reworked initialization from
dbaba47085b0c unconditionally calls split_lock_verify_msr() from
split_lock_init().

After the elaborate checks in cpu_set_core_cap_bits() this seems like an
oversight. The following simple patch fixes our regression by checking
for X86_FEATURE_SPLIT_LOCK_DETECT before accessing the TEST_CTRL MSR.

Please CC me on replies - I am not subscribed to the LKML.

Kind regards,

Ben

[1] https://github.com/kernkonzept/uvmm

-- 
Benjamin Lamowski - +49.351.41883235
Operating Systems Engineer - https://www.kernkonzept.com

Kernkonzept GmbH.  Sitz: Dresden.  Amtsgericht Dresden, HRB 31129.
GeschÃftsfÃhrer: Dr.-Ing. Michael Hohmuth