ADDED: So in the interrupt handler the kernel could evict all user space pages from cache before returning control to user space so it could not use the timing attack on the cache of the speculative execution of Mov rbx,[rax+Someusermodeaddress] on the address rax+Someusermodeaddress.
mov rax, [Somekerneladdress]
would trigger an interrupt even on speculative execution as described on https://cyber.wtf/2017/07/28/negative-result-reading-kernel-...
ADDED: So in the interrupt handler the kernel could evict all user space pages from cache before returning control to user space so it could not use the timing attack on the cache of the speculative execution of Mov rbx,[rax+Someusermodeaddress] on the address rax+Someusermodeaddress.