On Fri, Sep 24, 2021 at 05:55:25PM -0700, Sean Christopherson wrote:
> From: Jing Zhang <jingzhangos@xxxxxxxxxx>
>
> Add a "blocking" stat that userspace can use to detect the case where a
> vCPU is not being run because of a vCPU/guest action, e.g. HLT or WFS on
> x86, WFI on arm64, etc... Current guest/host/halt stats don't show this
> well, e.g. if a guest halts for a long period of time then the vCPU could
> appear pathologically blocked due to a host condition, when in reality the
> vCPU has been put into a not-runnable state by the guest.
>
> Originally-by: Cannon Matthews <cannonmatthews@xxxxxxxxxx>
> Suggested-by: Sean Christopherson <seanjc@xxxxxxxxxx>
> Signed-off-by: Jing Zhang <jingzhangos@xxxxxxxxxx>
> [sean: renamed stat to "blocking", massaged changelog]
> Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
Reviewed-by: David Matlack <dmatlack@xxxxxxxxxx>
> ---
> include/linux/kvm_host.h | 3 ++-
> include/linux/kvm_types.h | 1 +
> virt/kvm/kvm_main.c | 2 ++
> 3 files changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 655c2b24db2d..9bb1972e396a 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -1453,7 +1453,8 @@ struct _kvm_stats_desc {
> STATS_DESC_LOGHIST_TIME_NSEC(VCPU_GENERIC, halt_poll_fail_hist, \
> HALT_POLL_HIST_COUNT), \
> STATS_DESC_LOGHIST_TIME_NSEC(VCPU_GENERIC, halt_wait_hist, \
> - HALT_POLL_HIST_COUNT)
> + HALT_POLL_HIST_COUNT), \
> + STATS_DESC_ICOUNTER(VCPU_GENERIC, blocking)
>
> extern struct dentry *kvm_debugfs_dir;
>
> diff --git a/include/linux/kvm_types.h b/include/linux/kvm_types.h
> index 2237abb93ccd..c4f9257bf32d 100644
> --- a/include/linux/kvm_types.h
> +++ b/include/linux/kvm_types.h
> @@ -94,6 +94,7 @@ struct kvm_vcpu_stat_generic {
> u64 halt_poll_success_hist[HALT_POLL_HIST_COUNT];
> u64 halt_poll_fail_hist[HALT_POLL_HIST_COUNT];
> u64 halt_wait_hist[HALT_POLL_HIST_COUNT];
> + u64 blocking;
> };
>
> #define KVM_STATS_NAME_SIZE 48
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index fe34457530c2..2980d2b88559 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -3208,6 +3208,7 @@ bool kvm_vcpu_block(struct kvm_vcpu *vcpu)
> {
> bool waited = false;
>
> + vcpu->stat.generic.blocking = 1;
> kvm_arch_vcpu_blocking(vcpu);
>
> prepare_to_rcuwait(&vcpu->wait);
> @@ -3223,6 +3224,7 @@ bool kvm_vcpu_block(struct kvm_vcpu *vcpu)
> finish_rcuwait(&vcpu->wait);
>
> kvm_arch_vcpu_unblocking(vcpu);
> + vcpu->stat.generic.blocking = 0;
>
> return waited;
> }
> --
> 2.33.0.685.g46640cef36-goog
>
