On Wed, Aug 04, 2021 at 08:58:10AM +0000, Oliver Upton wrote:
> In some instances, a VMM may want to update the guest's counter-timer
> offset in a transparent manner, meaning that changes to the hardware
> value do not affect the synthetic register presented to the guest or the
> VMM through said guest's architectural state. Lay the groundwork to
> separate guest offset register writes from the hardware values utilized
> by KVM.
>
> Signed-off-by: Oliver Upton <oupton@xxxxxxxxxx>
> ---
> arch/arm64/kvm/arch_timer.c | 48 ++++++++++++++++++++++++++++++++----
> include/kvm/arm_arch_timer.h | 3 +++
> 2 files changed, 46 insertions(+), 5 deletions(-)
>
> diff --git a/arch/arm64/kvm/arch_timer.c b/arch/arm64/kvm/arch_timer.c
> index c0101db75ad4..4c2b763a8849 100644
> --- a/arch/arm64/kvm/arch_timer.c
> +++ b/arch/arm64/kvm/arch_timer.c
> @@ -87,6 +87,18 @@ static u64 timer_get_offset(struct arch_timer_context *ctxt)
> struct kvm_vcpu *vcpu = ctxt->vcpu;
>
> switch(arch_timer_ctx_index(ctxt)) {
> + case TIMER_VTIMER:
> + return ctxt->host_offset;
> + default:
> + return 0;
> + }
> +}
> +
> +static u64 timer_get_guest_offset(struct arch_timer_context *ctxt)
> +{
> + struct kvm_vcpu *vcpu = ctxt->vcpu;
> +
> + switch (arch_timer_ctx_index(ctxt)) {
> case TIMER_VTIMER:
> return __vcpu_sys_reg(vcpu, CNTVOFF_EL2);
> default:
> @@ -132,13 +144,31 @@ static void timer_set_offset(struct arch_timer_context *ctxt, u64 offset)
>
> switch(arch_timer_ctx_index(ctxt)) {
> case TIMER_VTIMER:
> - __vcpu_sys_reg(vcpu, CNTVOFF_EL2) = offset;
> + ctxt->host_offset = offset;
> break;
> default:
> WARN(offset, "timer %ld\n", arch_timer_ctx_index(ctxt));
> }
> }
>
> +static void timer_set_guest_offset(struct arch_timer_context *ctxt, u64 offset)
> +{
> + struct kvm_vcpu *vcpu = ctxt->vcpu;
> +
> + switch (arch_timer_ctx_index(ctxt)) {
> + case TIMER_VTIMER: {
> + u64 host_offset = timer_get_offset(ctxt);
> +
> + host_offset += offset - __vcpu_sys_reg(vcpu, CNTVOFF_EL2);
> + __vcpu_sys_reg(vcpu, CNTVOFF_EL2) = offset;
> + timer_set_offset(ctxt, host_offset);
> + break;
> + }
> + default:
> + WARN_ONCE(offset, "timer %ld\n", arch_timer_ctx_index(ctxt));
> + }
> +}
> +
> u64 kvm_phys_timer_read(void)
> {
> return timecounter->cc->read(timecounter->cc);
> @@ -749,7 +779,8 @@ int kvm_timer_vcpu_reset(struct kvm_vcpu *vcpu)
>
> /* Make offset updates for all timer contexts atomic */
> static void update_timer_offset(struct kvm_vcpu *vcpu,
> - enum kvm_arch_timers timer, u64 offset)
> + enum kvm_arch_timers timer, u64 offset,
> + bool guest_visible)
> {
> int i;
> struct kvm *kvm = vcpu->kvm;
> @@ -758,13 +789,20 @@ static void update_timer_offset(struct kvm_vcpu *vcpu,
> lockdep_assert_held(&kvm->lock);
>
> kvm_for_each_vcpu(i, tmp, kvm)
> - timer_set_offset(vcpu_get_timer(tmp, timer), offset);
> + if (guest_visible)
> + timer_set_guest_offset(vcpu_get_timer(tmp, timer),
> + offset);
> + else
> + timer_set_offset(vcpu_get_timer(tmp, timer), offset);
>
> /*
> * When called from the vcpu create path, the CPU being created is not
> * included in the loop above, so we just set it here as well.
> */
> - timer_set_offset(vcpu_get_timer(vcpu, timer), offset);
> + if (guest_visible)
> + timer_set_guest_offset(vcpu_get_timer(vcpu, timer), offset);
> + else
> + timer_set_offset(vcpu_get_timer(vcpu, timer), offset);
> }
>
> static void update_vtimer_cntvoff(struct kvm_vcpu *vcpu, u64 cntvoff)
> @@ -772,7 +810,7 @@ static void update_vtimer_cntvoff(struct kvm_vcpu *vcpu, u64 cntvoff)
> struct kvm *kvm = vcpu->kvm;
>
> mutex_lock(&kvm->lock);
> - update_timer_offset(vcpu, TIMER_VTIMER, cntvoff);
> + update_timer_offset(vcpu, TIMER_VTIMER, cntvoff, true);
> mutex_unlock(&kvm->lock);
> }
>
> diff --git a/include/kvm/arm_arch_timer.h b/include/kvm/arm_arch_timer.h
> index 51c19381108c..9d65d4a29f81 100644
> --- a/include/kvm/arm_arch_timer.h
> +++ b/include/kvm/arm_arch_timer.h
> @@ -42,6 +42,9 @@ struct arch_timer_context {
> /* Duplicated state from arch_timer.c for convenience */
> u32 host_timer_irq;
> u32 host_timer_irq_flags;
> +
> + /* offset relative to the host's physical counter-timer */
> + u64 host_offset;
> };
>
> struct timer_map {
> --
> 2.32.0.605.g8dce9f2422-goog
>
Reviewed-by: Andrew Jones <drjones@xxxxxxxxxx>
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