Subject: [kvm-unit-tests PATCH v9 13/31] powerpc: Add rtas stop-self support

From: Nicholas Piggin <[email-masked]>
Date: Sat, 4 May 2024 22:28:19 +1000

In preparation for improved SMP support, add stop-self support to the
harness. This is non-trivial because it requires an unlocked rtas
call: a CPU can't be holding a spin lock when it goes offline or it
will deadlock other CPUs. rtas permits stop-self to be called without
serialising all other rtas operations.

Reviewed-by: Thomas Huth <[email-masked]>
Signed-off-by: Nicholas Piggin <[email-masked]>
---
 lib/powerpc/asm/rtas.h |  2 ++
 lib/powerpc/rtas.c     | 78 +++++++++++++++++++++++++++++++++---------
 2 files changed, 64 insertions(+), 16 deletions(-)

diff --git a/lib/powerpc/asm/rtas.h b/lib/powerpc/asm/rtas.h
index 6fb407a18..364bf9355 100644
--- a/lib/powerpc/asm/rtas.h
+++ b/lib/powerpc/asm/rtas.h
@@ -23,8 +23,10 @@ struct rtas_args {
 extern void rtas_init(void);
 extern int rtas_token(const char *service, uint32_t *token);
 extern int rtas_call(int token, int nargs, int nret, int *outputs, ...);
+extern int rtas_call_unlocked(struct rtas_args *args, int token, int nargs, int nret, int *outputs, ...);
 
 extern void rtas_power_off(void);
+extern void rtas_stop_self(void);
 #endif /* __ASSEMBLY__ */
 
 #define RTAS_MSR_MASK 0xfffffffffffffffe
diff --git a/lib/powerpc/rtas.c b/lib/powerpc/rtas.c
index 41c0a243e..b477a38e0 100644
--- a/lib/powerpc/rtas.c
+++ b/lib/powerpc/rtas.c
@@ -87,40 +87,86 @@ int rtas_token(const char *service, uint32_t *token)
 	return 0;
 }
 
-int rtas_call(int token, int nargs, int nret, int *outputs, ...)
+static void __rtas_call(struct rtas_args *args)
 {
-	va_list list;
-	int ret, i;
+	enter_rtas(__pa(args));
+}
 
-	spin_lock(&rtas_lock);
+static int rtas_call_unlocked_va(struct rtas_args *args,
+			  int token, int nargs, int nret, int *outputs,
+			  va_list list)
+{
+	int ret, i;
 
-	rtas_args.token = cpu_to_be32(token);
-	rtas_args.nargs = cpu_to_be32(nargs);
-	rtas_args.nret = cpu_to_be32(nret);
-	rtas_args.rets = &rtas_args.args[nargs];
+	args->token = cpu_to_be32(token);
+	args->nargs = cpu_to_be32(nargs);
+	args->nret = cpu_to_be32(nret);
+	args->rets = &args->args[nargs];
 
-	va_start(list, outputs);
 	for (i = 0; i < nargs; ++i)
-		rtas_args.args[i] = cpu_to_be32(va_arg(list, u32));
-	va_end(list);
+		args->args[i] = cpu_to_be32(va_arg(list, u32));
 
 	for (i = 0; i < nret; ++i)
-		rtas_args.rets[i] = 0;
+		args->rets[i] = 0;
 
-	enter_rtas(__pa(&rtas_args));
+	__rtas_call(args);
 
 	if (nret > 1 && outputs != NULL)
 		for (i = 0; i < nret - 1; ++i)
-			outputs[i] = be32_to_cpu(rtas_args.rets[i + 1]);
+			outputs[i] = be32_to_cpu(args->rets[i + 1]);
+
+	ret = nret > 0 ? be32_to_cpu(args->rets[0]) : 0;
+
+	return ret;
+}
+
+int rtas_call_unlocked(struct rtas_args *args, int token, int nargs, int nret, int *outputs, ...)
+{
+	va_list list;
+	int ret;
 
-	ret = nret > 0 ? be32_to_cpu(rtas_args.rets[0]) : 0;
+	va_start(list, outputs);
+	ret = rtas_call_unlocked_va(args, token, nargs, nret, outputs, list);
+	va_end(list);
+
+	return ret;
+}
+
+int rtas_call(int token, int nargs, int nret, int *outputs, ...)
+{
+	va_list list;
+	int ret;
+
+	spin_lock(&rtas_lock);
+
+	va_start(list, outputs);
+	ret = rtas_call_unlocked_va(&rtas_args, token, nargs, nret, outputs, list);
+	va_end(list);
 
 	spin_unlock(&rtas_lock);
+
 	return ret;
 }
 
+void rtas_stop_self(void)
+{
+	struct rtas_args args;
+	uint32_t token;
+	int ret;
+
+	ret = rtas_token("stop-self", &token);
+	if (ret) {
+		puts("RTAS stop-self not available\n");
+		return;
+	}
+
+	ret = rtas_call_unlocked(&args, token, 0, 1, NULL);
+	printf("RTAS stop-self returned %d\n", ret);
+}
+
 void rtas_power_off(void)
 {
+	struct rtas_args args;
 	uint32_t token;
 	int ret;
 
@@ -130,6 +176,6 @@ void rtas_power_off(void)
 		return;
 	}
 
-	ret = rtas_call(token, 2, 1, NULL, -1, -1);
+	ret = rtas_call_unlocked(&args, token, 2, 1, NULL, -1, -1);
 	printf("RTAS power-off returned %d\n", ret);
 }
-- 
2.43.0