KVM/arm64 fixes for 6.3, part #2
Fixes for a rather interesting set of bugs relating to the MMU:
- Read the MMU notifier seq before dropping the mmap lock to guard
against reading a potentially stale VMA
- Disable interrupts when walking user page tables to protect against
the page table being freed
- Read the MTE permissions for the VMA within the mmap lock critical
section, avoiding the use of a potentally stale VMA pointer
Additionally, some fixes targeting the vPMU:
- Return the sum of the current perf event value and PMC snapshot for
reads from userspace
- Don't save the value of guest writes to PMCR_EL0.{C,P}, which could
otherwise lead to userspace erroneously resetting the vPMU during VM
save/restore