On 10/04/2015 11:11, Marc Zyngier wrote: >> Good idea! Does ARM have a way to do "lazy" save/restore? On x86 we >> know if the FP/SIMD state was in use on the host, and we can force an >> exit the first time the guest uses the FP/SIMD. >> >> On ARM, it wouldn't be a problem to handle this kind of exit straight in >> EL2 (similar to the hack Ard used when playing with memory attributes). > > We already do this on the 32bit port, and it works fine. > > I did some experimentations on arm64 a long while ago (see the > kvm-arm64/lazy-fp branch in my tree), and it wasn't that great, > apparently because aarch64 userspace tends to be much more FP happy than > aarch32, but I'm not completely sure about it. Also this is from a time > when I didn't have much HW to play with... > > Maybe I should resurrect it and compare it to what this patch does, just > as a comparison point. This patch looks like very nice low-hanging fruit anyway. Would you like to have it in 4.1? Paolo -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
