This prevents the application's thread from moving cores, but doesn't prevent an unrelated thread from using that core (especially in a hypervised environment). That unrelated thread could still perform those attacks against the application's thread.
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Would a thread-per-core architecture help mitigate security vulnerabilities like spectre and meltdown?
This prevents the application's thread from moving cores, but doesn't prevent an unrelated thread from using that core (especially in a hypervised environment). That unrelated thread could still perform those attacks against the application's thread.
Threads are still going to make syscalls into kernel code, so... not as much, no.
You are better with processes per core, with no threads.