On Mon, Oct 22, 2012 at 03:05:58PM +0200, Jan Kiszka wrote: > On 2012-10-22 14:58, Avi Kivity wrote: > > On 10/22/2012 02:55 PM, Jan Kiszka wrote: > >>> Since the userspace change is needed the idea is dead, but if we could > >>> implement it I do not see how it can hurt the latency if it would be the > >>> only mechanism to use coalesced mmio buffer. Checking that the ring buffer > >>> is empty is cheap and if it is not empty it means that kernel just saved > >>> you a lot of 8 bytes exists so even after iterating over all the entries there > >>> you still saved a lot of time. > >> > >> When taking an exit for A, I'm not interesting in flushing stuff for B > >> unless I have a dependency. Thus, buffers would have to be per device > >> before extending their use. > > > > Any mmio exit has to flush everything. For example a DMA caused by an > > e1000 write has to see any writes to the framebuffer, in case the guest > > is transmitting its framebuffer to the outside world. > > We already flush when that crazy guest actually accesses the region, no > need to do this unconditionally. > What if framebuffer is accessed from inside the kernel? Is this case handled? -- Gleb. -- 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
