Looks like support for this was not fully added; my apologies for closing this bug too early.
Adding full support for strong-on-weak emulation would be simple, at least when it comes to memory ordering. The slowdown would be huge though, see Figure 12 in http://www.cs.columbia.edu/~cota/pubs/cota_cgo17.pdf (i.e. ~2x hmean overhead for SPEC). The good news is that with hardware support this overhead is ~0 (see SAO in that figure). The other feature that is not yet implemented in upstream QEMU is the correct emulation of LL/SC, although for most code out there this shouldn't be an issue in practice given that most parallel code relies on cmpxchg, not on LL/SC pairs. I'm reopening this bug an Cc'ing a few people who are more familiar with the current code than I am in case I missed anything. -- You received this bug notification because you are a member of qemu- devel-ml, which is subscribed to QEMU. https://bugs.launchpad.net/bugs/1735049 Title: Need MTTCG support for x86 guests Status in QEMU: Fix Released Bug description: MTTCG support is notably absent for x86_64 guests. The last Wiki update on MTTCG was back in 2015, and I am having some difficulty determining the current status of the underlying requirements to enable this feature on x86 hosts. For instance, has support for strong-on-weak memory consistency been added into QEMU GIT at this point? Thanks! To manage notifications about this bug go to: https://bugs.launchpad.net/qemu/+bug/1735049/+subscriptions