On Wed, 16 Oct 2019 at 15:34, Andrew Jones <address@hidden> wrote:
v2:
- move from RFC status to v1
- put kvm_arm_vm_state_change() in kvm.c to share among kvm32.c and kvm64.c
- add r-b's from Richard
This series is inspired by a series[1] posted by Bijan Mottahedeh about
a year ago. The problem described in the cover letter of [1] is easily
reproducible and some users would like to have the option to avoid it.
However the solution, which is to adjust the virtual counter offset each
time the VM transitions to the running state, introduces a different
problem, which is that the virtual and physical counters diverge. As
described in the cover letter of [1] this divergence is easily observed
when comparing the output of `date` and `hwclock` after suspending the
guest, waiting a while, and then resuming it. Because this different
problem may actually be worse for some users, unlike [1], the series
posted here makes the virtual counter offset adjustment optional and not
even enabled by default. Besides the adjustment being optional, this
series approaches the needed changes differently to apply them in more
appropriate locations. Finally, unlike [1], this series doesn't attempt
to measure "pause time" itself. Simply using QEMU_CLOCK_VIRTUAL, which
only ticks when the VM is not stopped, is sufficient.
So I guess my overall question is "what is the x86 solution to
this problem, and why is this all arm-specific?" It would also
be helpful to know how it fits into all the other proposals regarding
time in VMs.