The architectural feature FEAT_ETS (Enhanced Translation
Synchronization) is a set of tightened guarantees about memory
ordering involving translation table walks:
* if memory access RW1 is ordered-before memory access RW2 then it
is also ordered-before any translation table walk generated by RW2
that generates a translation fault, address size fault or access
fault
* TLB maintenance on non-exec-permission translations is guaranteed
complete after a DSB (ie it does not need the context
synchronization event that you have to have if you don’t have
FEAT_ETS)
For QEMU’s implementation we don’t reorder translation table walk
accesses, and we guarantee to finish the TLB maintenance as soon as
the TLB op is done (the tlb_flush functions will complete at the end
of the TLB, and TLB ops always end the TB because they’re sysreg