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KVM: x86: Trace all APICv inhibit changes and capture overall status 

Trace all APICv inhibit changes instead of just those that result in
APICv being (un)inhibited, and log the current state.  Debugging why
APICv isn't working is frustrating as it's hard to see why APICv is still
inhibited, and logging only the first inhibition means unnecessary onion
peeling.

Opportunistically drop the export of the tracepoint, it is not and should
not be used by vendor code due to the need to serialize toggling via
apicv_update_lock.

Note, using the common flow means kvm_apicv_init() switched from atomic
to non-atomic bitwise operations.  The VM is unreachable at init, so
non-atomic is perfectly ok.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20220311043517.17027-4-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Sean Christopherson 2022-03-11 04:35:17 +00:00 committed by Paolo Bonzini
parent 320af55a93
commit 4f4c4a3ee5
2 changed files with 29 additions and 18 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

18
arch/x86/kvm/trace.h
View File

@ -1339,23 +1339,25 @@ TRACE_EVENT(kvm_hv_stimer_cleanup,
__entry->vcpu_id, __entry->timer_index)
);
TRACE_EVENT(kvm_apicv_update_request,
TP_PROTO(int reason, bool activate),
TP_ARGS(reason, activate),
TRACE_EVENT(kvm_apicv_inhibit_changed,
TP_PROTO(int reason, bool set, unsigned long inhibits),
TP_ARGS(reason, set, inhibits),
TP_STRUCT__entry(
__field(int, reason)
__field(bool, activate)
__field(bool, set)
__field(unsigned long, inhibits)
),
TP_fast_assign(
__entry->reason = reason;
__entry->activate = activate;
__entry->set = set;
__entry->inhibits = inhibits;
),
TP_printk("%s reason=%u",
__entry->activate ? "activate" : "deactivate",
__entry->reason)
TP_printk("%s reason=%u, inhibits=0x%lx",
__entry->set ? "set" : "cleared",
__entry->reason, __entry->inhibits)
);
TRACE_EVENT(kvm_apicv_accept_irq,

29
arch/x86/kvm/x86.c
View File

@ -9062,15 +9062,29 @@ bool kvm_apicv_activated(struct kvm *kvm)
}
EXPORT_SYMBOL_GPL(kvm_apicv_activated);
static void set_or_clear_apicv_inhibit(unsigned long *inhibits,
enum kvm_apicv_inhibit reason, bool set)
{
if (set)
__set_bit(reason, inhibits);
else
__clear_bit(reason, inhibits);
trace_kvm_apicv_inhibit_changed(reason, set, *inhibits);
}
static void kvm_apicv_init(struct kvm *kvm)
{
unsigned long *inhibits = &kvm->arch.apicv_inhibit_reasons;
init_rwsem(&kvm->arch.apicv_update_lock);
set_bit(APICV_INHIBIT_REASON_ABSENT,
&kvm->arch.apicv_inhibit_reasons);
set_or_clear_apicv_inhibit(inhibits, APICV_INHIBIT_REASON_ABSENT, true);
if (!enable_apicv)
set_bit(APICV_INHIBIT_REASON_DISABLE,
&kvm->arch.apicv_inhibit_reasons);
set_or_clear_apicv_inhibit(inhibits,
APICV_INHIBIT_REASON_ABSENT, true);
}
static void kvm_sched_yield(struct kvm_vcpu *vcpu, unsigned long dest_id)
@ -9756,13 +9770,9 @@ void __kvm_set_or_clear_apicv_inhibit(struct kvm *kvm,
old = new = kvm->arch.apicv_inhibit_reasons;
if (set)
__set_bit(reason, &new);
else
__clear_bit(reason, &new);
set_or_clear_apicv_inhibit(&new, reason, set);
if (!!old != !!new) {
trace_kvm_apicv_update_request(reason, !set);
/*
* Kick all vCPUs before setting apicv_inhibit_reasons to avoid
* false positives in the sanity check WARN in svm_vcpu_run().
@ -12945,7 +12955,6 @@ EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_pi_irte_update);
EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_avic_unaccelerated_access);
EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_avic_incomplete_ipi);
EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_avic_ga_log);
EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_apicv_update_request);
EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_apicv_accept_irq);
EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_vmgexit_enter);
EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_vmgexit_exit);