On Fri, Sep 24, 2021 at 05:55:24PM -0700, Sean Christopherson wrote:
> Factor out the "block" part of kvm_vcpu_halt() so that x86 can emulate
> non-halt wait/sleep/block conditions that should not be subjected to
> halt-polling.
>
> No functional change intended.
>
> Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
Reviewed-by: David Matlack <dmatlack@xxxxxxxxxx>
> ---
> include/linux/kvm_host.h | 1 +
> virt/kvm/kvm_main.c | 50 ++++++++++++++++++++++++++++------------
> 2 files changed, 36 insertions(+), 15 deletions(-)
>
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index d2a8be3fb9ba..655c2b24db2d 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -966,6 +966,7 @@ void kvm_sigset_activate(struct kvm_vcpu *vcpu);
> void kvm_sigset_deactivate(struct kvm_vcpu *vcpu);
>
> void kvm_vcpu_halt(struct kvm_vcpu *vcpu);
> +bool kvm_vcpu_block(struct kvm_vcpu *vcpu);
> void kvm_arch_vcpu_blocking(struct kvm_vcpu *vcpu);
> void kvm_arch_vcpu_unblocking(struct kvm_vcpu *vcpu);
> bool kvm_vcpu_wake_up(struct kvm_vcpu *vcpu);
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 280cf1dca7db..fe34457530c2 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -3199,6 +3199,34 @@ static int kvm_vcpu_check_block(struct kvm_vcpu *vcpu)
> return ret;
> }
>
> +/*
> + * Block the vCPU until the vCPU is runnable, an event arrives, or a signal is
> + * pending. This is mostly used when halting a vCPU, but may also be used
> + * directly for other vCPU non-runnable states, e.g. x86's Wait-For-SIPI.
> + */
> +bool kvm_vcpu_block(struct kvm_vcpu *vcpu)
> +{
> + bool waited = false;
> +
> + kvm_arch_vcpu_blocking(vcpu);
> +
> + prepare_to_rcuwait(&vcpu->wait);
> + for (;;) {
> + set_current_state(TASK_INTERRUPTIBLE);
> +
> + if (kvm_vcpu_check_block(vcpu) < 0)
> + break;
> +
> + waited = true;
> + schedule();
> + }
> + finish_rcuwait(&vcpu->wait);
> +
> + kvm_arch_vcpu_unblocking(vcpu);
> +
> + return waited;
> +}
> +
> static inline void update_halt_poll_stats(struct kvm_vcpu *vcpu, ktime_t start,
> ktime_t end, bool success)
> {
> @@ -3221,6 +3249,12 @@ static inline void update_halt_poll_stats(struct kvm_vcpu *vcpu, ktime_t start,
> }
> }
>
> +/*
> + * Emulate a vCPU halt condition, e.g. HLT on x86, WFI on arm, etc... If halt
> + * polling is enabled, busy wait for a short time before blocking to avoid the
> + * expensive block+unblock sequence if a wake event arrives soon after the vCPU
> + * is halted.
> + */
> void kvm_vcpu_halt(struct kvm_vcpu *vcpu)
> {
> bool halt_poll_allowed = !kvm_arch_no_poll(vcpu);
> @@ -3245,21 +3279,7 @@ void kvm_vcpu_halt(struct kvm_vcpu *vcpu)
> } while (kvm_vcpu_can_poll(cur, stop));
> }
>
> - kvm_arch_vcpu_blocking(vcpu);
> -
> - prepare_to_rcuwait(&vcpu->wait);
> - for (;;) {
> - set_current_state(TASK_INTERRUPTIBLE);
> -
> - if (kvm_vcpu_check_block(vcpu) < 0)
> - break;
> -
> - waited = true;
> - schedule();
> - }
> - finish_rcuwait(&vcpu->wait);
> -
> - kvm_arch_vcpu_unblocking(vcpu);
> + waited = kvm_vcpu_block(vcpu);
>
> cur = ktime_get();
> if (waited) {
> --
> 2.33.0.685.g46640cef36-goog
>
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