On 19.09.19 17:03, Thomas Gleixner wrote: > When working on a way to move out the posix cpu timer expiry out of the > timer interrupt context, I noticed that KVM is not handling pending task > work before entering a guest. A quick hack was to add that to the x86 KVM > handling loop. The discussion ended with a request to make this a generic > infrastructure possible with also moving the per arch implementations of > the enter from and return to user space handling generic. > > https://lore.kernel.org/r/89E42BCC-47A8-458B-B06A-D6A20D20512C@xxxxxxxxxxxxxx > > You asked for it, so don't complain that you have to review it :) > > The series implements the syscall enter/exit and the general exit to > userspace work handling along with the pre guest enter functionality. > > The series converts x86 and ARM64. x86 is fully tested including selftests > etc. ARM64 is only compile tested for now as my only ARM64 testbox is not > available right now. It seems that s390x would also need to look into TIF_NOTIFY_PENDING before entering a KVM guest. Given that the s390x entry path is still in assembler this might not be something to do quickly. Would it make sense to actually start with a minimal solution (e.g. one that provides notify_resume_pending like your original patch) as a fix. That would also be simple to backport. And then we can do the proper rework on top. Or do we consider anything that depends on TIF_NOTIFY_PENDING before entering a guest as not important enough for stable? After all the vcpu_run ioctl almost never returns to userspace and nothing was obviously broken. Another question: Are there callbacks due to TIF_NOTIFY_PENDING that should NOT happen as long as we stay in the vpcu loop?
