On Mon, Oct 24, 2011 at 07:05:08PM +0200, Michael S. Tsirkin wrote: > On Mon, Oct 24, 2011 at 06:10:28PM +0200, Jan Kiszka wrote: > > On 2011-10-24 18:05, Michael S. Tsirkin wrote: > > >> This is what I have in mind: > > >> - devices set PBA bit if MSI message cannot be sent due to mask (*) > > >> - core checks&clears PBA bit on unmask, injects message if bit was set > > >> - devices clear PBA bit if message reason is resolved before unmask (*) > > > > > > OK, but practically, when exactly does the device clear PBA? > > > > Consider a network adapter that signals messages in a RX ring: If the > > corresponding vector is masked while the guest empties the ring, I > > strongly assume that the device is supposed to take back the pending bit > > in that case so that there is no interrupt inject on a later vector > > unmask operation. > > > > Jan > > Do you mean virtio here? Do you expect this optimization to give > a significant performance gain?
It would also be challenging to implement this in a race free manner. Clearing on interrupt status read seems straight-forward. > > -- > > Siemens AG, Corporate Technology, CT T DE IT 1 > > Corporate Competence Center Embedded Linux -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
