On Mon, Jun 29, 2009 at 12:44:53PM +0300, Avi Kivity wrote: > On 06/29/2009 12:23 PM, Michael S. Tsirkin wrote: >> On Mon, Jun 29, 2009 at 11:37:00AM +0300, Avi Kivity wrote: >> >>> On 06/28/2009 10:34 PM, Michael S. Tsirkin wrote: >>> >>>> This changes bus accesses to use high-level kvm_io_bus_read/kvm_io_bus_write >>>> functions, which utilize read/write semaphore intead of mutex. in_range now >>>> becomes unused so it is removed from device ops in favor of read/write >>>> callbacks performing range checks internally. >>>> >>>> This allows aliasing (mostly for in-kernel virtio), as well as better error >>>> handling by making it possible to pass errors up to userspace. And it's enough >>>> to look at the diffstat to see that it's a better API anyway. >>>> >>>> While we are at it, document locking rules for kvm_io_device_ops. >>>> >>>> Note: since the use of the new bus_lock is localized to a small number of >>>> places, it will be easy to switch to srcu in the future if we so desire. >>>> >>>> >>> Looks good. But please split into a locking change patch and an API >>> change patch (in whatever order makes more sense). >>> >>> I think you can reuse slots_lock instead of adding a new lock. IIRC >>> slots_lock is already taken for read everywhere, so you only need to >>> take it for write when registering things. >>> >> >> IMO this will make it harder to convert to rcu down the line. >> As it is we just grep for bus_lock and replace with rcu. >> While possibly slots_lock can be converted to rcu as well, >> let's do it one thing at a time. >> > > We can convert it to rcu indepenently of other things protected by > slots_lock; no need to do everything at the same time. Yes but once we merge locks, it will be harder to split them out. I know I can now do grep bus_lock and find all places affected, if I reuse slot_lock this information is lost. No? -- MST -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
