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...; metadata is accessed through a direct pointer. > > > > The difference in ways you handle metadata and data is what is > > now coming and messing everything up. > > > I do propose soemthing like this in the past: > https://www.spinics.net/lists/linux-virtualization/msg36824.html. But looks > like you have some concern about its locality. Right and it doesn't go away. You'll need to come up with a test that messes it up and triggers a worst-case scenario, so we can measure how bad is that worst-case. > But the problem still there, GUP can do page fault,...

On Fri, Aug 02, 2019 at 05:40:07PM +0800, Jason Wang wrote: > Btw, I come up another idea, that is to disable preemption when vhost thread > need to access the memory. Then register preempt notifier and if vhost > thread is preempted, we're sure no one will access the memory and can do the > cleanup. Great, more notifiers :( Maybe can live with 1- disable preemption while using

On Fri, Aug 02, 2019 at 05:40:07PM +0800, Jason Wang wrote: > Btw, I come up another idea, that is to disable preemption when vhost thread > need to access the memory. Then register preempt notifier and if vhost > thread is preempted, we're sure no one will access the memory and can do the > cleanup. Great, more notifiers :( Maybe can live with 1- disable preemption while using

...ith this patch series that only > metadata is accessed through a direct pointer. > > The difference in ways you handle metadata and data is what is > now coming and messing everything up. I do propose soemthing like this in the past: https://www.spinics.net/lists/linux-virtualization/msg36824.html. But looks like you have some concern about its locality. But the problem still there, GUP can do page fault, so still need to synchronize it with MMU notifiers. The solution might be something like moving GUP to a dedicated kind of vhost work. > > So if continuing the direct map a...