powerpc/pseries: Fix endian problems with LE migration

RTAS events require arguments be passed in big endian while hypercalls
have their arguments passed in registers and the values should therefore
be in CPU endian.

The "ibm,suspend_me" 'RTAS' call makes a sequence of hypercalls to setup
one true RTAS call. This means that "ibm,suspend_me" is handled
specially in the ppc_rtas() syscall.

The ppc_rtas() syscall has its arguments in big endian and can therefore
pass these arguments directly to the RTAS call. "ibm,suspend_me" is
handled specially from within ppc_rtas() (by calling rtas_ibm_suspend_me())
which has left an endian bug on little endian systems due to the
requirement of hypercalls. The return value from rtas_ibm_suspend_me()
gets returned in cpu endian, and is left unconverted, also a bug on
little endian systems.

rtas_ibm_suspend_me() does not actually make use of the rtas_args that
it is passed. This patch removes the convoluted use of the rtas_args
struct to pass params to rtas_ibm_suspend_me() in favour of passing what
it needs as actual arguments. This patch also ensures the two callers of
rtas_ibm_suspend_me() pass function parameters in cpu endian and in the
case of ppc_rtas(), converts the return value.

migrate_store() (the other caller of rtas_ibm_suspend_me()) is from a
sysfs file which deals with everything in cpu endian so this function
only underwent cleanup.

This patch has been tested with KVM both LE and BE and on PowerVM both
LE and BE. Under QEMU/KVM the migration happens without touching these
code pathes.

For PowerVM there is no obvious regression on BE and the LE code path
now provides the correct parameters to the hypervisor.
Signed-off-by: Cyril Bur <cyrilbur@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/include/asm/rtas.h

@@ -327,7 +327,7 @@ extern int rtas_suspend_cpu(struct rtas_suspend_me_data *data);
 extern int rtas_suspend_last_cpu(struct rtas_suspend_me_data *data);
 extern int rtas_online_cpus_mask(cpumask_var_t cpus);
 extern int rtas_offline_cpus_mask(cpumask_var_t cpus);
-extern int rtas_ibm_suspend_me(struct rtas_args *);
+extern int rtas_ibm_suspend_me(u64 handle, int *vasi_return);
 
 struct rtc_time;
 extern unsigned long rtas_get_boot_time(void);

arch/powerpc/kernel/rtas.c

@@ -897,7 +897,7 @@ int rtas_offline_cpus_mask(cpumask_var_t cpus)
 }
 EXPORT_SYMBOL(rtas_offline_cpus_mask);
 
-int rtas_ibm_suspend_me(struct rtas_args *args)
+int rtas_ibm_suspend_me(u64 handle, int *vasi_return)
 {
 	long state;
 	long rc;
@@ -911,8 +911,7 @@ int rtas_ibm_suspend_me(struct rtas_args *args)
 		return -ENOSYS;
 
 	/* Make sure the state is valid */
-	rc = plpar_hcall(H_VASI_STATE, retbuf,
-			 ((u64)args->args[0] << 32) | args->args[1]);
+	rc = plpar_hcall(H_VASI_STATE, retbuf, handle);
 
 	state = retbuf[0];
 
@@ -920,12 +919,12 @@ int rtas_ibm_suspend_me(struct rtas_args *args)
 		printk(KERN_ERR "rtas_ibm_suspend_me: vasi_state returned %ld\n",rc);
 		return rc;
 	} else if (state == H_VASI_ENABLED) {
-		args->args[args->nargs] = RTAS_NOT_SUSPENDABLE;
+		*vasi_return = RTAS_NOT_SUSPENDABLE;
 		return 0;
 	} else if (state != H_VASI_SUSPENDING) {
 		printk(KERN_ERR "rtas_ibm_suspend_me: vasi_state returned state %ld\n",
 		       state);
-		args->args[args->nargs] = -1;
+		*vasi_return = -1;
 		return 0;
 	}
 
@@ -973,7 +972,7 @@ int rtas_ibm_suspend_me(struct rtas_args *args)
 	return atomic_read(&data.error);
 }
 #else /* CONFIG_PPC_PSERIES */
-int rtas_ibm_suspend_me(struct rtas_args *args)
+int rtas_ibm_suspend_me(u64 handle, int *vasi_return)
 {
 	return -ENOSYS;
 }
@@ -1053,7 +1052,16 @@ asmlinkage int ppc_rtas(struct rtas_args __user *uargs)
 
 	/* Need to handle ibm,suspend_me call specially */
 	if (token == ibm_suspend_me_token) {
-		rc = rtas_ibm_suspend_me(&args);
+
+		/*
+		 * rtas_ibm_suspend_me assumes args are in cpu endian, or at least the
+		 * hcall within it requires it.
+		 */
+		int vasi_rc = 0;
+		u64 handle = ((u64)be32_to_cpu(args.args[0]) << 32)
+		              | be32_to_cpu(args.args[1]);
+		rc = rtas_ibm_suspend_me(handle, &vasi_rc);
+		args.rets[0] = cpu_to_be32(vasi_rc);
 		if (rc)
 			return rc;
 		goto copy_return;

arch/powerpc/platforms/pseries/mobility.c

@@ -316,34 +316,24 @@ void post_mobility_fixup(void)
 static ssize_t migrate_store(struct class *class, struct class_attribute *attr,
 			     const char *buf, size_t count)
 {
-	struct rtas_args args;
 	u64 streamid;
 	int rc;
+	int vasi_rc = 0;
 
 	rc = kstrtou64(buf, 0, &streamid);
 	if (rc)
 		return rc;
 
-	memset(&args, 0, sizeof(args));
-	args.token = rtas_token("ibm,suspend-me");
-	args.nargs = 2;
-	args.nret = 1;
-
-	args.args[0] = streamid >> 32 ;
-	args.args[1] = streamid & 0xffffffff;
-	args.rets = &args.args[args.nargs];
-
 	do {
-		args.rets[0] = 0;
-		rc = rtas_ibm_suspend_me(&args);
-		if (!rc && args.rets[0] == RTAS_NOT_SUSPENDABLE)
+		rc = rtas_ibm_suspend_me(streamid, &vasi_rc);
+		if (!rc && vasi_rc == RTAS_NOT_SUSPENDABLE)
 			ssleep(1);
-	} while (!rc && args.rets[0] == RTAS_NOT_SUSPENDABLE);
+	} while (!rc && vasi_rc == RTAS_NOT_SUSPENDABLE);
 
 	if (rc)
 		return rc;
-	else if (args.rets[0])
-		return args.rets[0];
+	if (vasi_rc)
+		return vasi_rc;
 
 	post_mobility_fixup();
 	return count;