xen: bug fixes for 4.7-rc6

- Fix two bugs in the handling of xenbus transactions.
 - Make the xen acpi driver compatible with Xen 4.7.
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Merge tag 'for-linus-4.7b-rc6-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip

Pull xen bug fixes from David Vrabel:

 - Fix two bugs in the handling of xenbus transactions.

 - Make the xen acpi driver compatible with Xen 4.7.

* tag 'for-linus-4.7b-rc6-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip:
  xen/acpi: allow xen-acpi-processor driver to load on Xen 4.7
  xenbus: simplify xenbus_dev_request_and_reply()
  xenbus: don't bail early from xenbus_dev_request_and_reply()
  xenbus: don't BUG() on user mode induced condition

drivers/xen/xen-acpi-processor.c

@@ -423,36 +423,7 @@ upload:
 
 	return 0;
 }
-static int __init check_prereq(void)
-{
-	struct cpuinfo_x86 *c = &cpu_data(0);
 
-	if (!xen_initial_domain())
-		return -ENODEV;
-
-	if (!acpi_gbl_FADT.smi_command)
-		return -ENODEV;
-
-	if (c->x86_vendor == X86_VENDOR_INTEL) {
-		if (!cpu_has(c, X86_FEATURE_EST))
-			return -ENODEV;
-
-		return 0;
-	}
-	if (c->x86_vendor == X86_VENDOR_AMD) {
-		/* Copied from powernow-k8.h, can't include ../cpufreq/powernow
-		 * as we get compile warnings for the static functions.
-		 */
-#define CPUID_FREQ_VOLT_CAPABILITIES    0x80000007
-#define USE_HW_PSTATE                   0x00000080
-		u32 eax, ebx, ecx, edx;
-		cpuid(CPUID_FREQ_VOLT_CAPABILITIES, &eax, &ebx, &ecx, &edx);
-		if ((edx & USE_HW_PSTATE) != USE_HW_PSTATE)
-			return -ENODEV;
-		return 0;
-	}
-	return -ENODEV;
-}
 /* acpi_perf_data is a pointer to percpu data. */
 static struct acpi_processor_performance __percpu *acpi_perf_data;
 
@@ -509,10 +480,10 @@ struct notifier_block xen_acpi_processor_resume_nb = {
 static int __init xen_acpi_processor_init(void)
 {
 	unsigned int i;
-	int rc = check_prereq();
+	int rc;
 
-	if (rc)
-		return rc;
+	if (!xen_initial_domain())
+		return -ENODEV;
 
 	nr_acpi_bits = get_max_acpi_id() + 1;
 	acpi_ids_done = kcalloc(BITS_TO_LONGS(nr_acpi_bits), sizeof(unsigned long), GFP_KERNEL);

drivers/xen/xenbus/xenbus_dev_frontend.c

@@ -316,11 +316,18 @@ static int xenbus_write_transaction(unsigned msg_type,
 			rc = -ENOMEM;
 			goto out;
 		}
+	} else {
+		list_for_each_entry(trans, &u->transactions, list)
+			if (trans->handle.id == u->u.msg.tx_id)
+				break;
+		if (&trans->list == &u->transactions)
+			return -ESRCH;
 	}
 
 	reply = xenbus_dev_request_and_reply(&u->u.msg);
 	if (IS_ERR(reply)) {
-		kfree(trans);
+		if (msg_type == XS_TRANSACTION_START)
+			kfree(trans);
 		rc = PTR_ERR(reply);
 		goto out;
 	}
@@ -333,12 +340,7 @@ static int xenbus_write_transaction(unsigned msg_type,
 			list_add(&trans->list, &u->transactions);
 		}
 	} else if (u->u.msg.type == XS_TRANSACTION_END) {
-		list_for_each_entry(trans, &u->transactions, list)
-			if (trans->handle.id == u->u.msg.tx_id)
-				break;
-		BUG_ON(&trans->list == &u->transactions);
 		list_del(&trans->list);
-
 		kfree(trans);
 	}
 

drivers/xen/xenbus/xenbus_xs.c

@@ -232,10 +232,10 @@ static void transaction_resume(void)
 void *xenbus_dev_request_and_reply(struct xsd_sockmsg *msg)
 {
 	void *ret;
-	struct xsd_sockmsg req_msg = *msg;
+	enum xsd_sockmsg_type type = msg->type;
 	int err;
 
-	if (req_msg.type == XS_TRANSACTION_START)
+	if (type == XS_TRANSACTION_START)
 		transaction_start();
 
 	mutex_lock(&xs_state.request_mutex);
@@ -249,12 +249,8 @@ void *xenbus_dev_request_and_reply(struct xsd_sockmsg *msg)
 
 	mutex_unlock(&xs_state.request_mutex);
 
-	if (IS_ERR(ret))
-		return ret;
-
 	if ((msg->type == XS_TRANSACTION_END) ||
-	    ((req_msg.type == XS_TRANSACTION_START) &&
-	     (msg->type == XS_ERROR)))
+	    ((type == XS_TRANSACTION_START) && (msg->type == XS_ERROR)))
 		transaction_end();
 
 	return ret;