Paolo Bonzini <[email protected]> writes: > On 29/04/20 11:36, Vitaly Kuznetsov wrote: >> + >> + if (__this_cpu_read(apf_reason.enabled)) { >> + reason = __this_cpu_read(apf_reason.reason); >> + if (reason == KVM_PV_REASON_PAGE_READY) { >> + token = __this_cpu_read(apf_reason.token); >> + /* >> + * Make sure we read 'token' before we reset >> + * 'reason' or it can get lost. >> + */ >> + mb(); >> + __this_cpu_write(apf_reason.reason, 0); >> + kvm_async_pf_task_wake(token); >> + } > > If tokens cannot be zero, could we avoid using reason for the page ready > interrupt (and ultimately retire "reason" completely)?
Yes, we can switch to using 'token' exclusively but personally I'm not sure it is worth it. We'll still have to have a hole and reason + token is only u64. Keeping 'reason' in place allows us to easily come up with any other type of notification through this mecanism (if the reson is ... then 'token' means ...). -- Vitaly
