On Tue, Jul 28, 2020 at 11:33 AM Oliver Upton <oupton@xxxxxxxxxx> wrote:
>
> On Tue, Jul 21, 2020 at 8:26 PM Oliver Upton <oupton@xxxxxxxxxx> wrote:
> >
> > To date, VMMs have typically restored the guest's TSCs by value using
> > the KVM_SET_MSRS ioctl for each vCPU. However, restoring the TSCs by
> > value introduces some challenges with synchronization as the TSCs
> > continue to tick throughout the restoration process. As such, KVM has
> > some heuristics around TSC writes to infer whether or not the guest or
> > host is attempting to synchronize the TSCs.
> >
> > Instead of guessing at the intentions of a VMM, it'd be better to
> > provide an interface that allows for explicit synchronization of the
> > guest's TSCs. To that end, this series introduces the
> > KVM_{GET,SET}_TSC_OFFSET ioctls, yielding control of the TSC offset to
> > userspace.
> >
> > v2 => v3:
> > - Mark kvm_write_tsc_offset() as static (whoops)
> >
> > v1 => v2:
> > - Added clarification to the documentation of KVM_SET_TSC_OFFSET to
> > indicate that it can be used instead of an IA32_TSC MSR restore
> > through KVM_SET_MSRS
> > - Fixed KVM_SET_TSC_OFFSET to participate in the existing TSC
> > synchronization heuristics, thereby enabling the KVM masterclock when
> > all vCPUs are in phase.
> >
> > Oliver Upton (4):
> > kvm: x86: refactor masterclock sync heuristics out of kvm_write_tsc
> > kvm: vmx: check tsc offsetting with nested_cpu_has()
> > selftests: kvm: use a helper function for reading cpuid
> > selftests: kvm: introduce tsc_offset_test
> >
> > Peter Hornyack (1):
> > kvm: x86: add KVM_{GET,SET}_TSC_OFFSET ioctls
> >
> > Documentation/virt/kvm/api.rst | 31 ++
> > arch/x86/include/asm/kvm_host.h | 1 +
> > arch/x86/kvm/vmx/vmx.c | 2 +-
> > arch/x86/kvm/x86.c | 147 ++++---
> > include/uapi/linux/kvm.h | 5 +
> > tools/testing/selftests/kvm/.gitignore | 1 +
> > tools/testing/selftests/kvm/Makefile | 1 +
> > .../testing/selftests/kvm/include/test_util.h | 3 +
> > .../selftests/kvm/include/x86_64/processor.h | 15 +
> > .../selftests/kvm/include/x86_64/svm_util.h | 10 +-
> > .../selftests/kvm/include/x86_64/vmx.h | 9 +
> > tools/testing/selftests/kvm/lib/kvm_util.c | 1 +
> > tools/testing/selftests/kvm/lib/x86_64/vmx.c | 11 +
> > .../selftests/kvm/x86_64/tsc_offset_test.c | 362 ++++++++++++++++++
> > 14 files changed, 550 insertions(+), 49 deletions(-)
> > create mode 100644 tools/testing/selftests/kvm/x86_64/tsc_offset_test.c
> >
> > --
> > 2.28.0.rc0.142.g3c755180ce-goog
> >
>
> Ping :)
Ping
