Merge tag 'char-misc-4.11-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc

Pull char/misc driver updates from Greg KH:
 "Here is the big char/misc driver patchset for 4.11-rc1.

  Lots of different driver subsystems updated here: rework for the
  hyperv subsystem to handle new platforms better, mei and w1 and extcon
  driver updates, as well as a number of other "minor" driver updates.

  All of these have been in linux-next for a while with no reported
  issues"

* tag 'char-misc-4.11-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc: (169 commits)
  goldfish: Sanitize the broken interrupt handler
  x86/platform/goldfish: Prevent unconditional loading
  vmbus: replace modulus operation with subtraction
  vmbus: constify parameters where possible
  vmbus: expose hv_begin/end_read
  vmbus: remove conditional locking of vmbus_write
  vmbus: add direct isr callback mode
  vmbus: change to per channel tasklet
  vmbus: put related per-cpu variable together
  vmbus: callback is in softirq not workqueue
  binder: Add support for file-descriptor arrays
  binder: Add support for scatter-gather
  binder: Add extra size to allocator
  binder: Refactor binder_transact()
  binder: Support multiple /dev instances
  binder: Deal with contexts in debugfs
  binder: Support multiple context managers
  binder: Split flat_binder_object
  auxdisplay: ht16k33: remove private workqueue
  auxdisplay: ht16k33: rework input device initialization
  ...

7 files changed, 480 insertions, 24 deletions

diff --git a/arch/x86/Kbuild b/arch/x86/Kbuild
index eb3abf8ac44e..586b786b3edf 100644
--- a/arch/x86/Kbuild
+++ b/arch/x86/Kbuild
@@ -7,6 +7,9 @@ obj-$(CONFIG_KVM) += kvm/
 # Xen paravirtualization support
 obj-$(CONFIG_XEN) += xen/
 
+# Hyper-V paravirtualization support
+obj-$(CONFIG_HYPERVISOR_GUEST) += hyperv/
+
 # lguest paravirtualization support
 obj-$(CONFIG_LGUEST_GUEST) += lguest/
 
diff --git a/arch/x86/hyperv/Makefile b/arch/x86/hyperv/Makefile
new file mode 100644
index 000000000000..171ae09864d7
--- /dev/null
+++ b/arch/x86/hyperv/Makefile
@@ -0,0 +1 @@
+obj-y		:= hv_init.o
diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
new file mode 100644
index 000000000000..db64baf0e500
--- /dev/null
+++ b/arch/x86/hyperv/hv_init.c
@@ -0,0 +1,277 @@
+/*
+ * X86 specific Hyper-V initialization code.
+ *
+ * Copyright (C) 2016, Microsoft, Inc.
+ *
+ * Author : K. Y. Srinivasan <kys@microsoft.com>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 as published
+ * by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
+ * NON INFRINGEMENT.  See the GNU General Public License for more
+ * details.
+ *
+ */
+
+#include <linux/types.h>
+#include <asm/hypervisor.h>
+#include <asm/hyperv.h>
+#include <asm/mshyperv.h>
+#include <linux/version.h>
+#include <linux/vmalloc.h>
+#include <linux/mm.h>
+#include <linux/clockchips.h>
+
+
+#ifdef CONFIG_X86_64
+
+static struct ms_hyperv_tsc_page *tsc_pg;
+
+static u64 read_hv_clock_tsc(struct clocksource *arg)
+{
+	u64 current_tick;
+
+	if (tsc_pg->tsc_sequence != 0) {
+		/*
+		 * Use the tsc page to compute the value.
+		 */
+
+		while (1) {
+			u64 tmp;
+			u32 sequence = tsc_pg->tsc_sequence;
+			u64 cur_tsc;
+			u64 scale = tsc_pg->tsc_scale;
+			s64 offset = tsc_pg->tsc_offset;
+
+			rdtscll(cur_tsc);
+			/* current_tick = ((cur_tsc *scale) >> 64) + offset */
+			asm("mulq %3"
+				: "=d" (current_tick), "=a" (tmp)
+				: "a" (cur_tsc), "r" (scale));
+
+			current_tick += offset;
+			if (tsc_pg->tsc_sequence == sequence)
+				return current_tick;
+
+			if (tsc_pg->tsc_sequence != 0)
+				continue;
+			/*
+			 * Fallback using MSR method.
+			 */
+			break;
+		}
+	}
+	rdmsrl(HV_X64_MSR_TIME_REF_COUNT, current_tick);
+	return current_tick;
+}
+
+static struct clocksource hyperv_cs_tsc = {
+		.name		= "hyperv_clocksource_tsc_page",
+		.rating		= 400,
+		.read		= read_hv_clock_tsc,
+		.mask		= CLOCKSOURCE_MASK(64),
+		.flags		= CLOCK_SOURCE_IS_CONTINUOUS,
+};
+#endif
+
+static u64 read_hv_clock_msr(struct clocksource *arg)
+{
+	u64 current_tick;
+	/*
+	 * Read the partition counter to get the current tick count. This count
+	 * is set to 0 when the partition is created and is incremented in
+	 * 100 nanosecond units.
+	 */
+	rdmsrl(HV_X64_MSR_TIME_REF_COUNT, current_tick);
+	return current_tick;
+}
+
+static struct clocksource hyperv_cs_msr = {
+	.name		= "hyperv_clocksource_msr",
+	.rating		= 400,
+	.read		= read_hv_clock_msr,
+	.mask		= CLOCKSOURCE_MASK(64),
+	.flags		= CLOCK_SOURCE_IS_CONTINUOUS,
+};
+
+static void *hypercall_pg;
+struct clocksource *hyperv_cs;
+EXPORT_SYMBOL_GPL(hyperv_cs);
+
+/*
+ * This function is to be invoked early in the boot sequence after the
+ * hypervisor has been detected.
+ *
+ * 1. Setup the hypercall page.
+ * 2. Register Hyper-V specific clocksource.
+ */
+void hyperv_init(void)
+{
+	u64 guest_id;
+	union hv_x64_msr_hypercall_contents hypercall_msr;
+
+	if (x86_hyper != &x86_hyper_ms_hyperv)
+		return;
+
+	/*
+	 * Setup the hypercall page and enable hypercalls.
+	 * 1. Register the guest ID
+	 * 2. Enable the hypercall and register the hypercall page
+	 */
+	guest_id = generate_guest_id(0, LINUX_VERSION_CODE, 0);
+	wrmsrl(HV_X64_MSR_GUEST_OS_ID, guest_id);
+
+	hypercall_pg  = __vmalloc(PAGE_SIZE, GFP_KERNEL, PAGE_KERNEL_RX);
+	if (hypercall_pg == NULL) {
+		wrmsrl(HV_X64_MSR_GUEST_OS_ID, 0);
+		return;
+	}
+
+	rdmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
+	hypercall_msr.enable = 1;
+	hypercall_msr.guest_physical_address = vmalloc_to_pfn(hypercall_pg);
+	wrmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
+
+	/*
+	 * Register Hyper-V specific clocksource.
+	 */
+#ifdef CONFIG_X86_64
+	if (ms_hyperv.features & HV_X64_MSR_REFERENCE_TSC_AVAILABLE) {
+		union hv_x64_msr_hypercall_contents tsc_msr;
+
+		tsc_pg = __vmalloc(PAGE_SIZE, GFP_KERNEL, PAGE_KERNEL);
+		if (!tsc_pg)
+			goto register_msr_cs;
+
+		hyperv_cs = &hyperv_cs_tsc;
+
+		rdmsrl(HV_X64_MSR_REFERENCE_TSC, tsc_msr.as_uint64);
+
+		tsc_msr.enable = 1;
+		tsc_msr.guest_physical_address = vmalloc_to_pfn(tsc_pg);
+
+		wrmsrl(HV_X64_MSR_REFERENCE_TSC, tsc_msr.as_uint64);
+		clocksource_register_hz(&hyperv_cs_tsc, NSEC_PER_SEC/100);
+		return;
+	}
+#endif
+	/*
+	 * For 32 bit guests just use the MSR based mechanism for reading
+	 * the partition counter.
+	 */
+
+register_msr_cs:
+	hyperv_cs = &hyperv_cs_msr;
+	if (ms_hyperv.features & HV_X64_MSR_TIME_REF_COUNT_AVAILABLE)
+		clocksource_register_hz(&hyperv_cs_msr, NSEC_PER_SEC/100);
+}
+
+/*
+ * This routine is called before kexec/kdump, it does the required cleanup.
+ */
+void hyperv_cleanup(void)
+{
+	union hv_x64_msr_hypercall_contents hypercall_msr;
+
+	/* Reset our OS id */
+	wrmsrl(HV_X64_MSR_GUEST_OS_ID, 0);
+
+	/* Reset the hypercall page */
+	hypercall_msr.as_uint64 = 0;
+	wrmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
+
+	/* Reset the TSC page */
+	hypercall_msr.as_uint64 = 0;
+	wrmsrl(HV_X64_MSR_REFERENCE_TSC, hypercall_msr.as_uint64);
+}
+EXPORT_SYMBOL_GPL(hyperv_cleanup);
+
+/*
+ * hv_do_hypercall- Invoke the specified hypercall
+ */
+u64 hv_do_hypercall(u64 control, void *input, void *output)
+{
+	u64 input_address = (input) ? virt_to_phys(input) : 0;
+	u64 output_address = (output) ? virt_to_phys(output) : 0;
+#ifdef CONFIG_X86_64
+	u64 hv_status = 0;
+
+	if (!hypercall_pg)
+		return (u64)ULLONG_MAX;
+
+	__asm__ __volatile__("mov %0, %%r8" : : "r" (output_address) : "r8");
+	__asm__ __volatile__("call *%3" : "=a" (hv_status) :
+			     "c" (control), "d" (input_address),
+			     "m" (hypercall_pg));
+
+	return hv_status;
+
+#else
+
+	u32 control_hi = control >> 32;
+	u32 control_lo = control & 0xFFFFFFFF;
+	u32 hv_status_hi = 1;
+	u32 hv_status_lo = 1;
+	u32 input_address_hi = input_address >> 32;
+	u32 input_address_lo = input_address & 0xFFFFFFFF;
+	u32 output_address_hi = output_address >> 32;
+	u32 output_address_lo = output_address & 0xFFFFFFFF;
+
+	if (!hypercall_pg)
+		return (u64)ULLONG_MAX;
+
+	__asm__ __volatile__ ("call *%8" : "=d"(hv_status_hi),
+			      "=a"(hv_status_lo) : "d" (control_hi),
+			      "a" (control_lo), "b" (input_address_hi),
+			      "c" (input_address_lo), "D"(output_address_hi),
+			      "S"(output_address_lo), "m" (hypercall_pg));
+
+	return hv_status_lo | ((u64)hv_status_hi << 32);
+#endif /* !x86_64 */
+}
+EXPORT_SYMBOL_GPL(hv_do_hypercall);
+
+void hyperv_report_panic(struct pt_regs *regs)
+{
+	static bool panic_reported;
+
+	/*
+	 * We prefer to report panic on 'die' chain as we have proper
+	 * registers to report, but if we miss it (e.g. on BUG()) we need
+	 * to report it on 'panic'.
+	 */
+	if (panic_reported)
+		return;
+	panic_reported = true;
+
+	wrmsrl(HV_X64_MSR_CRASH_P0, regs->ip);
+	wrmsrl(HV_X64_MSR_CRASH_P1, regs->ax);
+	wrmsrl(HV_X64_MSR_CRASH_P2, regs->bx);
+	wrmsrl(HV_X64_MSR_CRASH_P3, regs->cx);
+	wrmsrl(HV_X64_MSR_CRASH_P4, regs->dx);
+
+	/*
+	 * Let Hyper-V know there is crash data available
+	 */
+	wrmsrl(HV_X64_MSR_CRASH_CTL, HV_CRASH_CTL_CRASH_NOTIFY);
+}
+EXPORT_SYMBOL_GPL(hyperv_report_panic);
+
+bool hv_is_hypercall_page_setup(void)
+{
+	union hv_x64_msr_hypercall_contents hypercall_msr;
+
+	/* Check if the hypercall page is setup */
+	hypercall_msr.as_uint64 = 0;
+	rdmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
+
+	if (!hypercall_msr.enable)
+		return false;
+
+	return true;
+}
+EXPORT_SYMBOL_GPL(hv_is_hypercall_page_setup);
diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
index aaf59b7da98a..7c9c895432a9 100644
--- a/arch/x86/include/asm/mshyperv.h
+++ b/arch/x86/include/asm/mshyperv.h
@@ -3,8 +3,28 @@
 
 #include <linux/types.h>
 #include <linux/interrupt.h>
+#include <linux/clocksource.h>
 #include <asm/hyperv.h>
 
+/*
+ * The below CPUID leaves are present if VersionAndFeatures.HypervisorPresent
+ * is set by CPUID(HVCPUID_VERSION_FEATURES).
+ */
+enum hv_cpuid_function {
+	HVCPUID_VERSION_FEATURES		= 0x00000001,
+	HVCPUID_VENDOR_MAXFUNCTION		= 0x40000000,
+	HVCPUID_INTERFACE			= 0x40000001,
+
+	/*
+	 * The remaining functions depend on the value of
+	 * HVCPUID_INTERFACE
+	 */
+	HVCPUID_VERSION				= 0x40000002,
+	HVCPUID_FEATURES			= 0x40000003,
+	HVCPUID_ENLIGHTENMENT_INFO		= 0x40000004,
+	HVCPUID_IMPLEMENTATION_LIMITS		= 0x40000005,
+};
+
 struct ms_hyperv_info {
 	u32 features;
 	u32 misc_features;
@@ -13,6 +33,128 @@ struct ms_hyperv_info {
 
 extern struct ms_hyperv_info ms_hyperv;
 
+/*
+ * Declare the MSR used to setup pages used to communicate with the hypervisor.
+ */
+union hv_x64_msr_hypercall_contents {
+	u64 as_uint64;
+	struct {
+		u64 enable:1;
+		u64 reserved:11;
+		u64 guest_physical_address:52;
+	};
+};
+
+/*
+ * TSC page layout.
+ */
+
+struct ms_hyperv_tsc_page {
+	volatile u32 tsc_sequence;
+	u32 reserved1;
+	volatile u64 tsc_scale;
+	volatile s64 tsc_offset;
+	u64 reserved2[509];
+};
+
+/*
+ * The guest OS needs to register the guest ID with the hypervisor.
+ * The guest ID is a 64 bit entity and the structure of this ID is
+ * specified in the Hyper-V specification:
+ *
+ * msdn.microsoft.com/en-us/library/windows/hardware/ff542653%28v=vs.85%29.aspx
+ *
+ * While the current guideline does not specify how Linux guest ID(s)
+ * need to be generated, our plan is to publish the guidelines for
+ * Linux and other guest operating systems that currently are hosted
+ * on Hyper-V. The implementation here conforms to this yet
+ * unpublished guidelines.
+ *
+ *
+ * Bit(s)
+ * 63 - Indicates if the OS is Open Source or not; 1 is Open Source
+ * 62:56 - Os Type; Linux is 0x100
+ * 55:48 - Distro specific identification
+ * 47:16 - Linux kernel version number
+ * 15:0  - Distro specific identification
+ *
+ *
+ */
+
+#define HV_LINUX_VENDOR_ID              0x8100
+
+/*
+ * Generate the guest ID based on the guideline described above.
+ */
+
+static inline  __u64 generate_guest_id(__u64 d_info1, __u64 kernel_version,
+				       __u64 d_info2)
+{
+	__u64 guest_id = 0;
+
+	guest_id = (((__u64)HV_LINUX_VENDOR_ID) << 48);
+	guest_id |= (d_info1 << 48);
+	guest_id |= (kernel_version << 16);
+	guest_id |= d_info2;
+
+	return guest_id;
+}
+
+
+/* Free the message slot and signal end-of-message if required */
+static inline void vmbus_signal_eom(struct hv_message *msg, u32 old_msg_type)
+{
+	/*
+	 * On crash we're reading some other CPU's message page and we need
+	 * to be careful: this other CPU may already had cleared the header
+	 * and the host may already had delivered some other message there.
+	 * In case we blindly write msg->header.message_type we're going
+	 * to lose it. We can still lose a message of the same type but
+	 * we count on the fact that there can only be one
+	 * CHANNELMSG_UNLOAD_RESPONSE and we don't care about other messages
+	 * on crash.
+	 */
+	if (cmpxchg(&msg->header.message_type, old_msg_type,
+		    HVMSG_NONE) != old_msg_type)
+		return;
+
+	/*
+	 * Make sure the write to MessageType (ie set to
+	 * HVMSG_NONE) happens before we read the
+	 * MessagePending and EOMing. Otherwise, the EOMing
+	 * will not deliver any more messages since there is
+	 * no empty slot
+	 */
+	mb();
+
+	if (msg->header.message_flags.msg_pending) {
+		/*
+		 * This will cause message queue rescan to
+		 * possibly deliver another msg from the
+		 * hypervisor
+		 */
+		wrmsrl(HV_X64_MSR_EOM, 0);
+	}
+}
+
+#define hv_get_current_tick(tick) rdmsrl(HV_X64_MSR_TIME_REF_COUNT, tick)
+#define hv_init_timer(timer, tick) wrmsrl(timer, tick)
+#define hv_init_timer_config(config, val) wrmsrl(config, val)
+
+#define hv_get_simp(val) rdmsrl(HV_X64_MSR_SIMP, val)
+#define hv_set_simp(val) wrmsrl(HV_X64_MSR_SIMP, val)
+
+#define hv_get_siefp(val) rdmsrl(HV_X64_MSR_SIEFP, val)
+#define hv_set_siefp(val) wrmsrl(HV_X64_MSR_SIEFP, val)
+
+#define hv_get_synic_state(val) rdmsrl(HV_X64_MSR_SCONTROL, val)
+#define hv_set_synic_state(val) wrmsrl(HV_X64_MSR_SCONTROL, val)
+
+#define hv_get_vp_index(index) rdmsrl(HV_X64_MSR_VP_INDEX, index)
+
+#define hv_get_synint_state(int_num, val) rdmsrl(int_num, val)
+#define hv_set_synint_state(int_num, val) wrmsrl(int_num, val)
+
 void hyperv_callback_vector(void);
 #ifdef CONFIG_TRACING
 #define trace_hyperv_callback_vector hyperv_callback_vector
@@ -25,4 +167,13 @@ void hv_setup_kexec_handler(void (*handler)(void));
 void hv_remove_kexec_handler(void);
 void hv_setup_crash_handler(void (*handler)(struct pt_regs *regs));
 void hv_remove_crash_handler(void);
+
+#if IS_ENABLED(CONFIG_HYPERV)
+extern struct clocksource *hyperv_cs;
+
+void hyperv_init(void);
+void hyperv_report_panic(struct pt_regs *regs);
+bool hv_is_hypercall_page_setup(void);
+void hyperv_cleanup(void);
+#endif
 #endif
diff --git a/arch/x86/include/uapi/asm/hyperv.h b/arch/x86/include/uapi/asm/hyperv.h
index 9b1a91834ac8..3a20ccf787b8 100644
--- a/arch/x86/include/uapi/asm/hyperv.h
+++ b/arch/x86/include/uapi/asm/hyperv.h
@@ -73,6 +73,9 @@
   */
 #define HV_X64_MSR_STAT_PAGES_AVAILABLE		(1 << 8)
 
+/* Crash MSR available */
+#define HV_FEATURE_GUEST_CRASH_MSR_AVAILABLE (1 << 10)
+
 /*
  * Feature identification: EBX indicates which flags were specified at
  * partition creation. The format is the same as the partition creation
@@ -144,6 +147,11 @@
  */
 #define HV_X64_RELAXED_TIMING_RECOMMENDED	(1 << 5)
 
+/*
+ * Crash notification flag.
+ */
+#define HV_CRASH_CTL_CRASH_NOTIFY (1ULL << 63)
+
 /* MSR used to identify the guest OS. */
 #define HV_X64_MSR_GUEST_OS_ID			0x40000000
 
diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
index 65e20c97e04b..b5375b9497b3 100644
--- a/arch/x86/kernel/cpu/mshyperv.c
+++ b/arch/x86/kernel/cpu/mshyperv.c
@@ -133,26 +133,6 @@ static uint32_t  __init ms_hyperv_platform(void)
 	return 0;
 }
 
-static u64 read_hv_clock(struct clocksource *arg)
-{
-	u64 current_tick;
-	/*
-	 * Read the partition counter to get the current tick count. This count
-	 * is set to 0 when the partition is created and is incremented in
-	 * 100 nanosecond units.
-	 */
-	rdmsrl(HV_X64_MSR_TIME_REF_COUNT, current_tick);
-	return current_tick;
-}
-
-static struct clocksource hyperv_cs = {
-	.name		= "hyperv_clocksource",
-	.rating		= 400, /* use this when running on Hyperv*/
-	.read		= read_hv_clock,
-	.mask		= CLOCKSOURCE_MASK(64),
-	.flags		= CLOCK_SOURCE_IS_CONTINUOUS,
-};
-
 static unsigned char hv_get_nmi_reason(void)
 {
 	return 0;
@@ -180,6 +160,11 @@ static int hv_nmi_unknown(unsigned int val, struct pt_regs *regs)
 
 static void __init ms_hyperv_init_platform(void)
 {
+	int hv_host_info_eax;
+	int hv_host_info_ebx;
+	int hv_host_info_ecx;
+	int hv_host_info_edx;
+
 	/*
 	 * Extract the features and hints
 	 */
@@ -190,6 +175,21 @@ static void __init ms_hyperv_init_platform(void)
 	pr_info("HyperV: features 0x%x, hints 0x%x\n",
 		ms_hyperv.features, ms_hyperv.hints);
 
+	/*
+	 * Extract host information.
+	 */
+	if (cpuid_eax(HVCPUID_VENDOR_MAXFUNCTION) >= HVCPUID_VERSION) {
+		hv_host_info_eax = cpuid_eax(HVCPUID_VERSION);
+		hv_host_info_ebx = cpuid_ebx(HVCPUID_VERSION);
+		hv_host_info_ecx = cpuid_ecx(HVCPUID_VERSION);
+		hv_host_info_edx = cpuid_edx(HVCPUID_VERSION);
+
+		pr_info("Hyper-V Host Build:%d-%d.%d-%d-%d.%d\n",
+			hv_host_info_eax, hv_host_info_ebx >> 16,
+			hv_host_info_ebx & 0xFFFF, hv_host_info_ecx,
+			hv_host_info_edx >> 24, hv_host_info_edx & 0xFFFFFF);
+	}
+
 #ifdef CONFIG_X86_LOCAL_APIC
 	if (ms_hyperv.features & HV_X64_MSR_APIC_FREQUENCY_AVAILABLE) {
 		/*
@@ -208,9 +208,6 @@ static void __init ms_hyperv_init_platform(void)
 			     "hv_nmi_unknown");
 #endif
 
-	if (ms_hyperv.features & HV_X64_MSR_TIME_REF_COUNT_AVAILABLE)
-		clocksource_register_hz(&hyperv_cs, NSEC_PER_SEC/100);
-
 #ifdef CONFIG_X86_IO_APIC
 	no_timer_check = 1;
 #endif
@@ -227,6 +224,13 @@ static void __init ms_hyperv_init_platform(void)
 	 */
 	if (efi_enabled(EFI_BOOT))
 		x86_platform.get_nmi_reason = hv_get_nmi_reason;
+
+#if IS_ENABLED(CONFIG_HYPERV)
+	/*
+	 * Setup the hook to get control post apic initialization.
+	 */
+	x86_platform.apic_post_init = hyperv_init;
+#endif
 }
 
 const __refconst struct hypervisor_x86 x86_hyper_ms_hyperv = {
diff --git a/arch/x86/platform/goldfish/goldfish.c b/arch/x86/platform/goldfish/goldfish.c
index 1693107a518e..0d17c0aafeb1 100644
--- a/arch/x86/platform/goldfish/goldfish.c
+++ b/arch/x86/platform/goldfish/goldfish.c
@@ -42,10 +42,22 @@ static struct resource goldfish_pdev_bus_resources[] = {
 	}
 };
 
+static bool goldfish_enable __initdata;
+
+static int __init goldfish_setup(char *str)
+{
+	goldfish_enable = true;
+	return 0;
+}
+__setup("goldfish", goldfish_setup);
+
 static int __init goldfish_init(void)
 {
+	if (!goldfish_enable)
+		return -ENODEV;
+
 	platform_device_register_simple("goldfish_pdev_bus", -1,
-						goldfish_pdev_bus_resources, 2);
+					goldfish_pdev_bus_resources, 2);
 	return 0;
 }
 device_initcall(goldfish_init);