Re: [PATCH 08/10] KVM: x86: Remove per-vCPU "cache" of its reference pvclock

[Paul Durrant]

On 18/01/2025 00:55, Sean Christopherson wrote:
> Remove the per-vCPU "cache" of the reference pvclock and instead cache
> only the TSC shift+multiplier.  All other fields in pvclock are fully
> recomputed by kvm_guest_time_update(), i.e. aren't actually persisted.
>
> In addition to shaving a few bytes, explicitly tracking the TSC shift/mul
> fields makes it easier to see that those fields are tied to hw_tsc_khz
> (they exist to avoid having to do expensive math in the common case).
> And conversely, not tracking the other fields makes it easier to see that
> things like the version number are pulled from the guest's copy, not from
> KVM's reference.
>
> Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
> ---
>   arch/x86/include/asm/kvm_host.h |  3 ++-
>   arch/x86/kvm/x86.c              | 27 +++++++++++++++------------
>   arch/x86/kvm/xen.c              |  8 ++++----
>   3 files changed, 21 insertions(+), 17 deletions(-)

Reviewed-by: Paul Durrant <paul@xxxxxxx>