Part 1 of David's series to clean up the host-side mess of kvmclock. The cut
point in this version is still quite arbitrary, but what's left for "part 2"
fits nicely into 2-3 buckets:
1: Masterclock overhaul
2. New uAPI and tests
As mentioned elsewhere, my plan is to throw this into an unstable topic branch
asap so it can be used as a base for part 2, but will target 7.4, not 7.3. I
won't publish it to kvm-x86/next until 7.3-rc1, to avoid polluting linux-next,
and I'll rebase the whole thing on one of 7.3-rc1, 7.3-rc2, or an updated
kvm/next.
v9:
- Pull in "Compute kvmclock base without pvclock_gtod_data" before "Avoid NTP
frequency skew for KVM clock on 32-bit host" to avoid having to provide what
is effectively an open-coded version of ktime_mono_to_any() to avoid data
races. [Sashiko].
- Pull in use of kernel timekeeping snapshots, split in three patches purely
to aid review and bisection.
- Check and clear KVM_REQ_MASTERCLOCK_UPDATE in kvm_arch_vcpu_postcreate().
[me, Sashiko]
- Add the missing return value in "Move "no master clock" fallback from...".
[Sashiko]
v8:
- Obviously cut partway through the full series.
- Update commit references for 633d7652f80f ("KVM: x86/xen: Do not corrupt
KVM clock in kvm_xen_shared_info_init()").
- Chunk the "Restructure ..." patches into individual logical changes
("Restructure kvm_guest_time_update() for TSC upscaling" in particular was
quite gnarly).
- Ensure the TSC+freq pair during guest time updates happens on a single
CPU. [Sashiko]
- Keep __get_kvmclock() as a masterclock-specific helper to avoid deep
indentation and gotos.
- Do waaaaay too much spelunking to try piece together the history of some
of the many warts.
- Ensure preemption is disabled in get_kvmclock() when getting the TSC freq.
v7: https://lore.kernel.org/all/20260728144954.355376-1-dwmw2@infradead.org
David Woodhouse (14):
KVM: x86: Improve accuracy of KVM clock when TSC scaling is in force
KVM: x86: Explicitly disable TSC scaling without CONSTANT_TSC
KVM: x86: Activate master clock immediately on vCPU creation
KVM: x86: Compute kvmclock base without pvclock_gtod_data
KVM: x86: Avoid NTP frequency skew for KVM clock on 32-bit host
KVM: x86: Wrap all of __get_kvmclock_master_clock() with
CONFIG_X86_64=y
KVM: x86: Fall back to non-master-clock if clockread fails in
get_kvmclock()
KVM: x86: Fix KVM clock precision in get_kvmclock() with TSC scaling
KVM: x86: Use get_kvmclock() in kvm_get_wall_clock_epoch()
KVM: x86: Fix compute_guest_tsc() to handle negative time deltas
KVM: x86: Upscale TSC to "now", not master clock when updating PV
clocks
KVM: x86: Simplify and comment kvm_get_time_scale()
KVM: x86: Remove implicit rdtsc() from kvm_compute_l1_tsc_offset()
KVM: x86: Use kernel timekeeping snapshots for getting kvmclock time
since boot
Sean Christopherson (7):
KVM: x86: Update "last guest TSC" snapshot prior to enabling
IRQs/preemption
KVM: x86: Drop unnecessary CPU pinning when computing/getting kvmclock
KVM: x86: Move "no master clock" fallback from __get_kvmclock() to
get_kvmclock()
KVM: x86: Disable preemption, not IRQs, when getting TSC+freq pair
KVM: x86: Make master clock logic in guest PV clock updates 64-bit
only
KVM: x86: Use kernel timekeeping snapshot for monotonic clock
KVM: x86: Use kernel timekeeping snapshot to get walltime+TSC
arch/x86/include/asm/kvm_host.h | 6 +-
arch/x86/kvm/cpuid.c | 1 +
arch/x86/kvm/msrs.c | 3 +-
arch/x86/kvm/svm/svm.c | 3 +-
arch/x86/kvm/vmx/vmx.c | 10 +
arch/x86/kvm/x86.c | 491 +++++++++++++++-----------------
arch/x86/kvm/x86.h | 3 +-
7 files changed, 245 insertions(+), 272 deletions(-)
base-commit: 1b731e5ded480bd1e5546aed35584238661ce72e
--
2.55.0.679.g6767b8d81c-goog