[LTP] [PATCH v2 4/7] KVM: Add async communication helper functions

[Martin Doucha]

Some KVM tests need to communicate with VM controller program
without stopping guest execution. Add guest helper functions
for sending asynchronous guest signal to host and waiting for host
to acknowledge the signal. Add host helper functions for waiting
for guest signal and acknowledging it.

Test programs using these functions must have at least two host threads.

Signed-off-by: Martin Doucha <mdoucha@suse.cz>
---

Changes since v1:
- Use tst_clock_gettime() to measure timeout

 testcases/kernel/kvm/Makefile             |  1 +
 testcases/kernel/kvm/include/kvm_common.h |  8 ++++++
 testcases/kernel/kvm/include/kvm_guest.h  | 14 ++++++++++
 testcases/kernel/kvm/include/kvm_host.h   | 14 ++++++++++
 testcases/kernel/kvm/lib_guest.c          | 16 +++++++++++
 testcases/kernel/kvm/lib_host.c           | 33 +++++++++++++++++++++++
 6 files changed, 86 insertions(+)

diff --git a/testcases/kernel/kvm/Makefile b/testcases/kernel/kvm/Makefile
index e12cb4e98..501bb5a09 100644
--- a/testcases/kernel/kvm/Makefile
+++ b/testcases/kernel/kvm/Makefile
@@ -7,6 +7,7 @@ include $(top_srcdir)/include/mk/testcases.mk
 
 ASFLAGS =
 CPPFLAGS += -I$(abs_srcdir)/include
+LDLIBS += -lrt
 GUEST_CPPFLAGS = $(CPPFLAGS) -DCOMPILE_PAYLOAD
 GUEST_CFLAGS = -ffreestanding -O2 -Wall -fno-asynchronous-unwind-tables -mno-mmx -mno-sse
 GUEST_LDFLAGS = -nostdlib -Wl,--build-id=none -fno-stack-protector -z noexecstack
diff --git a/testcases/kernel/kvm/include/kvm_common.h b/testcases/kernel/kvm/include/kvm_common.h
index 4e81d8302..377e3f6aa 100644
--- a/testcases/kernel/kvm/include/kvm_common.h
+++ b/testcases/kernel/kvm/include/kvm_common.h
@@ -10,6 +10,14 @@
 
 #define KVM_TNONE	-1	/* "No result" status value */
 
+/*
+ * Result value for asynchronous notifications between guest and host.
+ * Do not use this value directly. Call tst_signal_host() or tst_wait_host()
+ * in guest code. The notification must be handled by another host thread
+ * and then the result value must be reset to KVM_TNONE.
+ */
+#define KVM_TSYNC	0xfe
+
 /*
  * Result value indicating end of test. If the test program exits using
  * the HLT instruction with any valid result value other than KVM_TEXIT or
diff --git a/testcases/kernel/kvm/include/kvm_guest.h b/testcases/kernel/kvm/include/kvm_guest.h
index ec13c5845..96f246155 100644
--- a/testcases/kernel/kvm/include/kvm_guest.h
+++ b/testcases/kernel/kvm/include/kvm_guest.h
@@ -64,6 +64,20 @@ void tst_brk_(const char *file, const int lineno, int result,
 	const char *message) __attribute__((noreturn));
 #define tst_brk(result, msg) tst_brk_(__FILE__, __LINE__, (result), (msg))
 
+/*
+ * Send asynchronous notification to host without stopping VM execution and
+ * return immediately. The notification must be handled by another host thread.
+ * The data argument will be passed to host in test_result->file_addr and
+ * can be used to send additional data both ways.
+ */
+void tst_signal_host(void *data);
+
+/*
+ * Call tst_signal_host(data) and wait for host to call
+ * tst_kvm_clear_guest_signal().
+ */
+void tst_wait_host(void *data);
+
 void *tst_heap_alloc_aligned(size_t size, size_t align);
 void *tst_heap_alloc(size_t size);
 
diff --git a/testcases/kernel/kvm/include/kvm_host.h b/testcases/kernel/kvm/include/kvm_host.h
index 2359944fd..3949dd040 100644
--- a/testcases/kernel/kvm/include/kvm_host.h
+++ b/testcases/kernel/kvm/include/kvm_host.h
@@ -134,4 +134,18 @@ void tst_kvm_run_instance(struct tst_kvm_instance *inst);
  */
 void tst_kvm_destroy_instance(struct tst_kvm_instance *inst);
 
+/*
+ * Wait for given VM to call tst_signal_host() or tst_wait_host(). Timeout
+ * value is in milliseconds. Zero means no wait, negative value means wait
+ * forever. Returns 0 if signal was received, KVM_TEXIT if the VM exited
+ * without sending a signal, or -1 if timeout was reached.
+ */
+int tst_kvm_wait_guest(struct tst_kvm_instance *inst, int timeout_ms);
+
+/*
+ * Clear VM signal sent by tst_signal_host(). If the VM is waiting
+ * in tst_wait_host(), this function will signal the VM to resume execution.
+ */
+void tst_kvm_clear_guest_signal(struct tst_kvm_instance *inst);
+
 #endif /* KVM_HOST_H_ */
diff --git a/testcases/kernel/kvm/lib_guest.c b/testcases/kernel/kvm/lib_guest.c
index d3b2ac3d5..f3e21d3d6 100644
--- a/testcases/kernel/kvm/lib_guest.c
+++ b/testcases/kernel/kvm/lib_guest.c
@@ -155,6 +155,22 @@ void tst_brk_(const char *file, const int lineno, int result,
 	kvm_exit();
 }
 
+void tst_signal_host(void *data)
+{
+	test_result->file_addr = (uintptr_t)data;
+	test_result->result = KVM_TSYNC;
+}
+
+void tst_wait_host(void *data)
+{
+	volatile int32_t *vres = &test_result->result;
+
+	tst_signal_host(data);
+
+	while (*vres != KVM_TNONE)
+		;
+}
+
 void tst_handle_interrupt(struct kvm_interrupt_frame *ifrm, long vector,
 	unsigned long errcode)
 {
diff --git a/testcases/kernel/kvm/lib_host.c b/testcases/kernel/kvm/lib_host.c
index 2782e68b0..2f524e3ce 100644
--- a/testcases/kernel/kvm/lib_host.c
+++ b/testcases/kernel/kvm/lib_host.c
@@ -10,6 +10,8 @@
 
 #define TST_NO_DEFAULT_MAIN
 #include "tst_test.h"
+#include "tst_clocks.h"
+#include "tst_timer.h"
 #include "kvm_host.h"
 
 static struct tst_kvm_instance test_vm = { .vm_fd = -1 };
@@ -272,6 +274,37 @@ void tst_kvm_destroy_instance(struct tst_kvm_instance *inst)
 	memset(inst->ram, 0, sizeof(inst->ram));
 }
 
+int tst_kvm_wait_guest(struct tst_kvm_instance *inst, int timeout_ms)
+{
+	volatile struct tst_kvm_result *result = inst->result;
+	int32_t res;
+	struct timespec start, now;
+
+	if (timeout_ms >= 0)
+		tst_clock_gettime(CLOCK_MONOTONIC, &start);
+
+	while ((res = result->result) != KVM_TSYNC) {
+		if (res == KVM_TEXIT)
+			return res;
+
+		if (timeout_ms >= 0) {
+			tst_clock_gettime(CLOCK_MONOTONIC, &now);
+
+			if (tst_timespec_diff_ms(now, start) >= timeout_ms)
+				return -1;
+		}
+
+		usleep(1000);
+	}
+
+	return 0;
+}
+
+void tst_kvm_clear_guest_signal(struct tst_kvm_instance *inst)
+{
+	inst->result->result = KVM_TNONE;
+}
+
 void tst_kvm_setup(void)
 {
 
-- 
2.40.0