On 1/23/19 11:30 AM, Paul Mackerras wrote: > On Wed, Jan 23, 2019 at 05:45:24PM +1100, Benjamin Herrenschmidt wrote: >> On Tue, 2019-01-22 at 16:26 +1100, Paul Mackerras wrote: >>> On Mon, Jan 07, 2019 at 08:10:05PM +0100, Cédric Le Goater wrote: >>>> Clear the ESB pages from the VMA of the IRQ being pass through to the >>>> guest and let the fault handler repopulate the VMA when the ESB pages >>>> are accessed for an EOI or for a trigger. >>> >>> Why do we want to do this? >>> >>> I don't see any possible advantage to removing the PTEs from the >>> userspace mapping. You'll need to explain further. >> >> Afaik bcs we change the mapping to point to the real HW irq ESB page >> instead of the "IPI" that was there at VM init time. yes exactly. You need to clean up the pages each time. > So that makes it sound like there is a whole lot going on that hasn't > even been hinted at in the patch descriptions... It sounds like we > need a good description of how all this works and fits together > somewhere under Documentation/. OK. I have started doing so for the models merged in QEMU but not yet for KVM. I will work on it. > In any case we need much more informative patch descriptions. I > realize that it's all currently in Cedric's head, but I bet that in > two or three years' time when we come to try to debug something, it > won't be in anyone's head... I agree. So, storing the ESB VMA under the KVM device is not shocking anyone ? Thanks, C.
