2024-04-29 15:59:57

by Alejandro Jimenez

Subject: [PATCH 1/4] KVM: x86: Expose per-vCPU APICv status

Expose the APICv activation status of individual vCPUs via the stats
subsystem. In special cases a vCPU's APICv can be deactivated/disabled
even though there are no VM-wide inhibition reasons. The only current
example of this is AVIC for a vCPU running in nested mode. This type of
inhibition is not recorded in the VM inhibit reasons or visible in
current tracepoints.

Signed-off-by: Alejandro Jimenez <[email protected]>
---
arch/x86/include/asm/kvm_host.h | 1 +
arch/x86/kvm/lapic.c | 1 +
arch/x86/kvm/x86.c | 2 ++
3 files changed, 4 insertions(+)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 1d13e3cd1dc5..12f30cb5c842 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1573,6 +1573,7 @@ struct kvm_vcpu_stat {
u64 preemption_other;
u64 guest_mode;
u64 notify_window_exits;
+ u64 apicv_active;
};

struct x86_instruction_info;
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index cf37586f0466..37fe75a5db8c 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -2872,6 +2872,7 @@ int kvm_create_lapic(struct kvm_vcpu *vcpu, int timer_advance_ns)
*/
if (enable_apicv) {
apic->apicv_active = true;
+ vcpu->stat.apicv_active = apic->apicv_active;
kvm_make_request(KVM_REQ_APICV_UPDATE, vcpu);
}

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index e9ef1fa4b90b..0451c4c8d731 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -304,6 +304,7 @@ const struct _kvm_stats_desc kvm_vcpu_stats_desc[] = {
STATS_DESC_COUNTER(VCPU, preemption_other),
STATS_DESC_IBOOLEAN(VCPU, guest_mode),
STATS_DESC_COUNTER(VCPU, notify_window_exits),
+ STATS_DESC_IBOOLEAN(VCPU, apicv_active),
};

const struct kvm_stats_header kvm_vcpu_stats_header = {
@@ -10625,6 +10626,7 @@ void __kvm_vcpu_update_apicv(struct kvm_vcpu *vcpu)
goto out;

apic->apicv_active = activate;
+ vcpu->stat.apicv_active = apic->apicv_active;
kvm_apic_update_apicv(vcpu);
static_call(kvm_x86_refresh_apicv_exec_ctrl)(vcpu);

--
2.39.3

2024-05-31 09:27:37

by Vasant Hegde

Subject: Re: [PATCH 1/4] KVM: x86: Expose per-vCPU APICv status

On 4/29/2024 9:27 PM, Alejandro Jimenez wrote:
> Expose the APICv activation status of individual vCPUs via the stats
> subsystem. In special cases a vCPU's APICv can be deactivated/disabled
> even though there are no VM-wide inhibition reasons. The only current
> example of this is AVIC for a vCPU running in nested mode. This type of
> inhibition is not recorded in the VM inhibit reasons or visible in
> current tracepoints.
>
> Signed-off-by: Alejandro Jimenez <[email protected]>


Reviewed-by: Vasant Hegde <[email protected]>

-Vasant

> ---
> arch/x86/include/asm/kvm_host.h | 1 +
> arch/x86/kvm/lapic.c | 1 +
> arch/x86/kvm/x86.c | 2 ++
> 3 files changed, 4 insertions(+)
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 1d13e3cd1dc5..12f30cb5c842 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -1573,6 +1573,7 @@ struct kvm_vcpu_stat {
> u64 preemption_other;
> u64 guest_mode;
> u64 notify_window_exits;
> + u64 apicv_active;
> };
>
> struct x86_instruction_info;
> diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
> index cf37586f0466..37fe75a5db8c 100644
> --- a/arch/x86/kvm/lapic.c
> +++ b/arch/x86/kvm/lapic.c
> @@ -2872,6 +2872,7 @@ int kvm_create_lapic(struct kvm_vcpu *vcpu, int timer_advance_ns)
> */
> if (enable_apicv) {
> apic->apicv_active = true;
> + vcpu->stat.apicv_active = apic->apicv_active;
> kvm_make_request(KVM_REQ_APICV_UPDATE, vcpu);
> }
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index e9ef1fa4b90b..0451c4c8d731 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -304,6 +304,7 @@ const struct _kvm_stats_desc kvm_vcpu_stats_desc[] = {
> STATS_DESC_COUNTER(VCPU, preemption_other),
> STATS_DESC_IBOOLEAN(VCPU, guest_mode),
> STATS_DESC_COUNTER(VCPU, notify_window_exits),
> + STATS_DESC_IBOOLEAN(VCPU, apicv_active),
> };
>
> const struct kvm_stats_header kvm_vcpu_stats_header = {
> @@ -10625,6 +10626,7 @@ void __kvm_vcpu_update_apicv(struct kvm_vcpu *vcpu)
> goto out;
>
> apic->apicv_active = activate;
> + vcpu->stat.apicv_active = apic->apicv_active;
> kvm_apic_update_apicv(vcpu);
> static_call(kvm_x86_refresh_apicv_exec_ctrl)(vcpu);
>

2024-06-04 00:18:36

by Sean Christopherson

Subject: Re: [PATCH 1/4] KVM: x86: Expose per-vCPU APICv status

On Mon, Apr 29, 2024, Alejandro Jimenez wrote:
> Expose the APICv activation status of individual vCPUs via the stats
> subsystem. In special cases a vCPU's APICv can be deactivated/disabled
> even though there are no VM-wide inhibition reasons. The only current
> example of this is AVIC for a vCPU running in nested mode. This type of
> inhibition is not recorded in the VM inhibit reasons or visible in
> current tracepoints.
>
> Signed-off-by: Alejandro Jimenez <[email protected]>
> ---
> arch/x86/include/asm/kvm_host.h | 1 +
> arch/x86/kvm/lapic.c | 1 +
> arch/x86/kvm/x86.c | 2 ++
> 3 files changed, 4 insertions(+)
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 1d13e3cd1dc5..12f30cb5c842 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -1573,6 +1573,7 @@ struct kvm_vcpu_stat {
> u64 preemption_other;
> u64 guest_mode;
> u64 notify_window_exits;
> + u64 apicv_active;

Hrm, do we really have no way to effectively symlink stats to internal state?
That seems like a flaw. It's obviously not the end of the world, but having to
burn 8 bytes per vCPU for boolean stats that are 1:1 reflections of KVM state is
going to be a deterrent for future stats.

> };
>
> struct x86_instruction_info;
> diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
> index cf37586f0466..37fe75a5db8c 100644
> --- a/arch/x86/kvm/lapic.c
> +++ b/arch/x86/kvm/lapic.c
> @@ -2872,6 +2872,7 @@ int kvm_create_lapic(struct kvm_vcpu *vcpu, int timer_advance_ns)
> */
> if (enable_apicv) {
> apic->apicv_active = true;
> + vcpu->stat.apicv_active = apic->apicv_active;
> kvm_make_request(KVM_REQ_APICV_UPDATE, vcpu);
> }
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index e9ef1fa4b90b..0451c4c8d731 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -304,6 +304,7 @@ const struct _kvm_stats_desc kvm_vcpu_stats_desc[] = {
> STATS_DESC_COUNTER(VCPU, preemption_other),
> STATS_DESC_IBOOLEAN(VCPU, guest_mode),
> STATS_DESC_COUNTER(VCPU, notify_window_exits),
> + STATS_DESC_IBOOLEAN(VCPU, apicv_active),
> };
>
> const struct kvm_stats_header kvm_vcpu_stats_header = {
> @@ -10625,6 +10626,7 @@ void __kvm_vcpu_update_apicv(struct kvm_vcpu *vcpu)
> goto out;
>
> apic->apicv_active = activate;
> + vcpu->stat.apicv_active = apic->apicv_active;
> kvm_apic_update_apicv(vcpu);
> static_call(kvm_x86_refresh_apicv_exec_ctrl)(vcpu);
>
> --
> 2.39.3
>