FEAT_ETS2 is a tighter set of guarantees about memory ordering
involving translation table walks than the old FEAT_ETS; FEAT_ETS has
been retired from the Arm ARM and the old ID_AA64MMFR1.ETS == 1
now gives no greater guarantees than ETS == 0.
FEAT_ETS2 requires:
* the virtual address of a load or store that appears in program
order after a DSB cannot be translated until after the DSB
completes (section B2.10.9)
* TLB maintenance operations that only affect translations without
execute permission are guaranteed complete after a DSB
(R_BLDZX)
* if a memory access RW2 is ordered-before memory access RW2,
then RW1 is also ordered-before any translation table walk
generated by RW2 that generates a Translation, Address size
or Access flag fault (R_NNFPF, I_CLGHP)
As with FEAT_ETS, QEMU is already compliant, because we do not
reorder translation table walk memory accesses relative to other
memory accesses, and we always guarantee to have finished TLB
maintenance as soon as the TLB op is done.
Update the documentation to list FEAT_ETS2 instead of the
no-longer-existent FEAT_ETS, and update the 'max' CPU ID registers.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-id: 20240418152004.2106516-4-peter.maydell@linaro.org
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