2019-06-13 19:22+0200, Paolo Bonzini: > Even when asynchronous page fault is disabled, KVM does not want to pause > the host if a guest triggers a page fault; instead it will put it into > an artificial HLT state that allows running other host processes while > allowing interrupt delivery into the guest. > > However, the way this feature is triggered is a bit confusing. > First, it is not used for page faults while a nested guest is > running: but this is not an issue since the artificial halt > is completely invisible to the guest, either L1 or L2. Second, > it is used even if kvm_halt_in_guest() returns true; in this case, > the guest probably should not pay the additional latency cost of the > artificial halt, and thus we should handle the page fault in a > completely synchronous way. > > By introducing a new function kvm_can_deliver_async_pf, this patch > commonizes the code that chooses whether to deliver an async page fault > (kvm_arch_async_page_not_present) and the code that chooses whether a > page fault should be handled synchronously (kvm_can_do_async_pf). > > Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx> > --- Reviewed-by: Radim Krčmář <rkrcmar@xxxxxxxxxx>
