Seems like linux isn’t properly checking for cpu arch and setting generic x86 flags, especially since it’s applying meltdown which really should not be set for Via anything.
The way the kernel logic works, is to apply all mitigations on x86 anything and then use certain flags to opt out specific mitigations on some CPU’s
Basically nobody bothered to code the mitigation exceptions for C7.
I’ve you’ve got a 5.2+ kernel just boot with mitigations=off flag.
C3/C7 is in order execution based with basic prefetch, no speculative execution of any sort. Hence spectre, meltdown, especially MDS (LOL!!!) the whole lot are impossible on the hardware.