KVM: arm64: Fix caching of host MDCR_EL2 value

At boot time, KVM stashes the host MDCR_EL2 value, but only does this
when the kernel is not running in hyp mode (i.e. is non-VHE). In these
cases, the stashed value of MDCR_EL2.HPMN happens to be zero, which can
lead to CONSTRAINED UNPREDICTABLE behaviour.

Since we use this value to derive the MDCR_EL2 value when switching
to/from a guest, after a guest have been run, the performance counters
do not behave as expected. This has been observed to result in accesses
via PMXEVTYPER_EL0 and PMXEVCNTR_EL0 not affecting the relevant
counters, resulting in events not being counted. In these cases, only
the fixed-purpose cycle counter appears to work as expected.

Fix this by always stashing the host MDCR_EL2 value, regardless of VHE.

Cc: Christopher Dall <[email protected]>
Cc: James Morse <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: [email protected]
Fixes: 1e947bad0b63b351 ("arm64: KVM: Skip HYP setup when already running in HYP")
Tested-by: Robin Murphy <[email protected]>
Signed-off-by: Mark Rutland <[email protected]>
Signed-off-by: Marc Zyngier <[email protected]>

0 files changed, 0 insertions, 0 deletions