[kvm-unit-tests PATCH v8 20/35] powerpc: Add rtas stop-self support

Nicholas Piggin
2024-04-05T08:37:12Z

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 <thuth@redhat.com>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
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