[PATCH v2 15/28] powerpc/rtas: dispatch partition migration requests to pseries

[Nathan Lynch]

sys_rtas() cannot call ibm,suspend-me directly in the same way it
handles other inputs. Instead it must dispatch the request to code
that can first perform the H_JOIN sequence before any call to
ibm,suspend-me can succeed. Over time kernel/rtas.c has accreted a fair
amount of platform-specific code to implement this.

Since a different, more robust implementation of the suspend sequence
is now in the pseries platform code, we want to dispatch the request
there.

Note that invoking ibm,suspend-me via the RTAS syscall is all but
deprecated; this change preserves ABI compatibility for old programs
while providing to them the benefit of the new partition suspend
implementation. This is a behavior change in that the kernel performs
the device tree update and firmware activation before returning, but
experimentation indicates this is tolerated fine by legacy user space.

Signed-off-by: Nathan Lynch <nathanl at linux.ibm.com>
---
 arch/powerpc/include/asm/rtas.h           | 5 +++++
 arch/powerpc/kernel/rtas.c                | 2 +-
 arch/powerpc/platforms/pseries/mobility.c | 5 +++++
 3 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/include/asm/rtas.h b/arch/powerpc/include/asm/rtas.h
index fdefe6a974eb..3b52d8574fcc 100644
--- a/arch/powerpc/include/asm/rtas.h
+++ b/arch/powerpc/include/asm/rtas.h
@@ -279,8 +279,13 @@ extern time64_t last_rtas_event;
 extern int clobbering_unread_rtas_event(void);
 extern int pseries_devicetree_update(s32 scope);
 extern void post_mobility_fixup(void);
+int rtas_syscall_dispatch_ibm_suspend_me(u64 handle);
 #else
 static inline int clobbering_unread_rtas_event(void) { return 0; }
+static inline int rtas_syscall_dispatch_ibm_suspend_me(u64 handle)
+{
+	return -EINVAL;
+}
 #endif
 
 #ifdef CONFIG_PPC_RTAS_DAEMON
diff --git a/arch/powerpc/kernel/rtas.c b/arch/powerpc/kernel/rtas.c
index 3a740ae933f8..d4b048571728 100644
--- a/arch/powerpc/kernel/rtas.c
+++ b/arch/powerpc/kernel/rtas.c
@@ -1272,7 +1272,7 @@ SYSCALL_DEFINE1(rtas, struct rtas_args __user *, uargs)
 		int rc = 0;
 		u64 handle = ((u64)be32_to_cpu(args.args[0]) << 32)
 		              | be32_to_cpu(args.args[1]);
-		rc = rtas_ibm_suspend_me_unsafe(handle);
+		rc = rtas_syscall_dispatch_ibm_suspend_me(handle);
 		if (rc == -EAGAIN)
 			args.rets[0] = cpu_to_be32(RTAS_NOT_SUSPENDABLE);
 		else if (rc == -EIO)
diff --git a/arch/powerpc/platforms/pseries/mobility.c b/arch/powerpc/platforms/pseries/mobility.c
index fe7e35cdc9d5..e670180f311d 100644
--- a/arch/powerpc/platforms/pseries/mobility.c
+++ b/arch/powerpc/platforms/pseries/mobility.c
@@ -615,6 +615,11 @@ static int pseries_migrate_partition(u64 handle)
 	return ret;
 }
 
+int rtas_syscall_dispatch_ibm_suspend_me(u64 handle)
+{
+	return pseries_migrate_partition(handle);
+}
+
 static ssize_t migration_store(struct class *class,
 			       struct class_attribute *attr, const char *buf,
 			       size_t count)
-- 
2.28.0