[PATCH v7 27/28] KVM: arm64: Add selftest event support to pKVM hyp

[Vincent Donnefort <vdonnefort@google.com>]

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 79019e11f529..522cccef32b7 100644
--- a/arch/arm64/include/asm/kvm_asm.h
+++ b/arch/arm64/include/asm/kvm_asm.h
@@ -94,6 +94,7 @@ enum __kvm_host_smccc_func {
 	__KVM_HOST_SMCCC_FUNC___pkvm_reset_tracing,
 	__KVM_HOST_SMCCC_FUNC___pkvm_swap_reader_tracing,
 	__KVM_HOST_SMCCC_FUNC___pkvm_enable_event,
+	__KVM_HOST_SMCCC_FUNC___pkvm_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 ce3953bc884a..3d1244972869 100644
--- a/arch/arm64/include/asm/kvm_hypevents.h
+++ b/arch/arm64/include/asm/kvm_hypevents.h
@@ -24,4 +24,18 @@ HYP_EVENT(hyp_exit,
 	),
 	HE_PRINTK()
 );
+
+#ifdef CONFIG_PKVM_SELFTESTS
+HYP_EVENT(selftest,
+	HE_PROTO(u64 id),
+	HE_STRUCT(
+		he_field(u64, id)
+	),
+	HE_ASSIGN(
+		__entry->id = id;
+	),
+	RE_PRINTK("id=%lld", __entry->id)
+);
 #endif
+
+#endif /* __ARM64_KVM_HYPEVENTS_H_ */
diff --git a/arch/arm64/kvm/Kconfig b/arch/arm64/kvm/Kconfig
index e06358aaf1af..dc2ac3049428 100644
--- a/arch/arm64/kvm/Kconfig
+++ b/arch/arm64/kvm/Kconfig
@@ -45,6 +45,7 @@ menuconfig KVM
 config NVHE_EL2_DEBUG
 	bool "Debug mode for non-VHE EL2 object"
 	depends on KVM
+	select PKVM_SELFTESTS
 	help
 	  Say Y here to enable the debug mode for the non-VHE KVM EL2 object.
 	  Failure reports will BUG() in the hypervisor. This is intended for
@@ -82,6 +83,15 @@ config PTDUMP_STAGE2_DEBUGFS
 
 	  If in doubt, say N.
 
+config PKVM_SELFTESTS
+	bool "Protected KVM hypervisor selftests"
+	depends on KVM
+	default n
+	help
+	  Say Y here to enable pKVM hypervisor testing infrastructure.
+
+	  If unsure, say N.
+
 config PKVM_TRACING
 	bool
 	depends on KVM
diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-main.c b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
index f8361520967b..81d8628a9047 100644
--- a/arch/arm64/kvm/hyp/nvhe/hyp-main.c
+++ b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
@@ -631,6 +631,20 @@ static void handle___pkvm_enable_event(struct kvm_cpu_context *host_ctxt)
 	cpu_reg(host_ctxt, 1) = __pkvm_enable_event(id, enable);
 }
 
+static void handle___pkvm_write_event(struct kvm_cpu_context *host_ctxt)
+{
+	int smc_ret = SMCCC_RET_NOT_SUPPORTED, ret = -EOPNOTSUPP;
+#ifdef CONFIG_PKVM_SELFTESTS
+	DECLARE_REG(u64, id, host_ctxt, 1);
+
+	trace_selftest(id);
+	smc_ret = SMCCC_RET_SUCCESS;
+	ret = 0;
+#endif
+	cpu_reg(host_ctxt, 0) = smc_ret;
+	cpu_reg(host_ctxt, 1) = ret;
+}
+
 typedef void (*hcall_t)(struct kvm_cpu_context *);
 
 #define HANDLE_FUNC(x)	[__KVM_HOST_SMCCC_FUNC_##x] = (hcall_t)handle_##x
@@ -677,6 +691,7 @@ static const hcall_t host_hcall[] = {
 	HANDLE_FUNC(__pkvm_reset_tracing),
 	HANDLE_FUNC(__pkvm_swap_reader_tracing),
 	HANDLE_FUNC(__pkvm_enable_event),
+	HANDLE_FUNC(__pkvm_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 73539f5b5e42..7d078f87f86d 100644
--- a/arch/arm64/kvm/hyp_trace.c
+++ b/arch/arm64/kvm/hyp_trace.c
@@ -318,8 +318,34 @@ static int hyp_trace_clock_show(struct seq_file *m, void *v)
 }
 DEFINE_SHOW_ATTRIBUTE(hyp_trace_clock);
 
+#ifdef CONFIG_PKVM_SELFTESTS
+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;
+
+	ret = kvm_call_hyp_nvhe(__pkvm_write_event, val);
+	if (ret)
+		return ret;
+
+	return cnt;
+}
+
+static const struct file_operations hyp_trace_write_event_fops = {
+	.write	= hyp_trace_write_event_write,
+};
+#endif
+
 static int hyp_trace_init_tracefs(struct dentry *d, void *priv)
 {
+#ifdef CONFIG_PKVM_SELFTESTS
+	tracefs_create_file("write_event", 0200, d, NULL, &hyp_trace_write_event_fops);
+#endif
 	return tracefs_create_file("trace_clock", 0440, d, NULL, &hyp_trace_clock_fops) ?
 		0 : -ENOMEM;
 }
diff --git a/tools/testing/selftests/ftrace/test.d/remotes/pkvm/trace.tc b/tools/testing/selftests/ftrace/test.d/remotes/pkvm/trace.tc
new file mode 100644
index 000000000000..49dca7c3861a
--- /dev/null
+++ b/tools/testing/selftests/ftrace/test.d/remotes/pkvm/trace.tc
@@ -0,0 +1,10 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+# description: Test pkvm hypervisor tracing pipe
+
+SOURCE_REMOTE_TEST=1
+. $TEST_DIR/remotes/trace_pipe.tc
+
+set -e
+setup_remote "hypervisor"
+test_trace
-- 
2.51.0.618.g983fd99d29-goog