[PATCH v14 29/30] KVM: arm64: Add selftest event support to nVHE/pKVM hyp

Vincent Donnefort
2026-03-09T16:26:32Z

Add a selftest event that can be triggered from a `write_event` tracefs
file. This intends to be used by trace remote selftests.

Signed-off-by: Vincent Donnefort <vdonnefort@google.com>

diff --git a/arch/arm64/include/asm/kvm_asm.h b/arch/arm64/include/asm/kvm_asm.h
index 47d250436f8c..c8eb992d3ac8 100644
--- a/arch/arm64/include/asm/kvm_asm.h
+++ b/arch/arm64/include/asm/kvm_asm.h
@@ -96,6 +96,7 @@ enum __kvm_host_smccc_func {
__KVM_HOST_SMCCC_FUNC___tracing_update_clock,
__KVM_HOST_SMCCC_FUNC___tracing_reset,
__KVM_HOST_SMCCC_FUNC___tracing_enable_event,
+ __KVM_HOST_SMCCC_FUNC___tracing_write_event,
};

#define DECLARE_KVM_VHE_SYM(sym) extern char sym[]
diff --git a/arch/arm64/include/asm/kvm_hypevents.h b/arch/arm64/include/asm/kvm_hypevents.h
index 221a1dacb2f0..743c49bd878f 100644
--- a/arch/arm64/include/asm/kvm_hypevents.h
+++ b/arch/arm64/include/asm/kvm_hypevents.h
@@ -46,4 +46,15 @@ HYP_EVENT(hyp_exit,
),
HE_PRINTK("reason=%s vcpu=%d", __hyp_enter_exit_reason_str(__entry->reason), __entry->vcpu)
);
+
+HYP_EVENT(selftest,
+ HE_PROTO(u64 id),
+ HE_STRUCT(
+ he_field(u64, id)
+ ),
+ HE_ASSIGN(
+ __entry->id = id;
+ ),
+ RE_PRINTK("id=%llu", __entry->id)
+);
#endif
diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-main.c b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
index 547d63679022..eff9cb208627 100644
--- a/arch/arm64/kvm/hyp/nvhe/hyp-main.c
+++ b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
@@ -643,6 +643,13 @@ static void handle___tracing_enable_event(struct kvm_cpu_context *host_ctxt)
cpu_reg(host_ctxt, 1) = __tracing_enable_event(id, enable);
}

+static void handle___tracing_write_event(struct kvm_cpu_context *host_ctxt)
+{
+ DECLARE_REG(u64, id, host_ctxt, 1);
+
+ trace_selftest(id);
+}
+
typedef void (*hcall_t)(struct kvm_cpu_context *);

#define HANDLE_FUNC(x) [__KVM_HOST_SMCCC_FUNC_##x] = (hcall_t)handle_##x
@@ -691,6 +698,7 @@ static const hcall_t host_hcall[] = {
HANDLE_FUNC(__tracing_update_clock),
HANDLE_FUNC(__tracing_reset),
HANDLE_FUNC(__tracing_enable_event),
+ HANDLE_FUNC(__tracing_write_event),
};

static void handle_host_hcall(struct kvm_cpu_context *host_ctxt)
diff --git a/arch/arm64/kvm/hyp_trace.c b/arch/arm64/kvm/hyp_trace.c
index 1ad6a55ba95c..c1e28f6581ab 100644
--- a/arch/arm64/kvm/hyp_trace.c
+++ b/arch/arm64/kvm/hyp_trace.c
@@ -348,8 +348,30 @@ static int hyp_trace_clock_show(struct seq_file *m, void *v)
}
DEFINE_SHOW_ATTRIBUTE(hyp_trace_clock);

+static ssize_t hyp_trace_write_event_write(struct file *f, const char __user *ubuf,
+ size_t cnt, loff_t *pos)
+{
+ unsigned long val;
+ int ret;
+
+ ret = kstrtoul_from_user(ubuf, cnt, 10, &val);
+ if (ret)
+ return ret;
+
+ kvm_call_hyp_nvhe(__tracing_write_event, val);
+
+ return cnt;
+}
+
+static const struct file_operations hyp_trace_write_event_fops = {
+ .write = hyp_trace_write_event_write,
+};
+
static int hyp_trace_init_tracefs(struct dentry *d, void *priv)
{
+ if (!tracefs_create_file("write_event", 0200, d, NULL, &hyp_trace_write_event_fops))
+ return -ENOMEM;
+
return tracefs_create_file("trace_clock", 0440, d, NULL, &hyp_trace_clock_fops) ?
0 : -ENOMEM;
}
--
2.53.0.473.g4a7958ca14-goog