On Thu, Jul 23, 2020 at 12:00:02AM +0200, Thomas Gleixner wrote: > From: Thomas Gleixner <tglx@xxxxxxxxxxxxx> > > Guests and user space share certain MSRs. KVM sets these MSRs to guest > values once and does not set them back to user space values on every VM > exit to spare the costly MSR operations. > > User return notifiers ensure that these MSRs are set back to the correct > values before returning to user space in exit_to_usermode_loop(). > > There is no reason to evaluate the TIF flag indicating that user return > notifiers need to be invoked in the loop. The important point is that they > are invoked before returning to user space. > > Move the invocation out of the loop into the section which does the last > preperatory steps before returning to user space. That section is not > preemptible and runs with interrupts disabled until the actual return. > > Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Reviewed-and-tested-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
