x86/efistub: Call Apple set_os protocol on dual GPU Intel Macs

0c18184d ("platform/x86: apple-gmux: support MMIO gmux on T2 Macs")
brought support for T2 Macs in apple-gmux. But in order to use dual GPU,
the integrated GPU has to be enabled. On such dual GPU EFI Macs, the EFI
stub needs to report that it is booting macOS in order to prevent the
firmware from disabling the iGPU.

This patch is also applicable for some non T2 Intel Macs.

Based on this patch for GRUB by Andreas Heider <andreas@heider.io>:
https://lists.gnu.org/archive/html/grub-devel/2013-12/msg00442.html

Credits also goto Kerem Karabay <kekrby@gmail.com> for helping porting
the patch to the Linux kernel.

Cc: Orlando Chamberlain <orlandoch.dev@gmail.com>
Signed-off-by: Aditya Garg <gargaditya08@live.com>
[ardb: limit scope using list of DMI matches provided by Lukas and Orlando]
Reviewed-by: Lukas Wunner <lukas@wunner.de>
Tested-by: Aditya Garg <gargaditya08@live.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

drivers/firmware/efi/libstub/x86-stub.c

@@ -225,6 +225,68 @@ static void retrieve_apple_device_properties(struct boot_params *boot_params)
 	}
 }
 
+static bool apple_match_product_name(void)
+{
+	static const char type1_product_matches[][15] = {
+		"MacBookPro11,3",
+		"MacBookPro11,5",
+		"MacBookPro13,3",
+		"MacBookPro14,3",
+		"MacBookPro15,1",
+		"MacBookPro15,3",
+		"MacBookPro16,1",
+		"MacBookPro16,4",
+	};
+	const struct efi_smbios_type1_record *record;
+	const u8 *product;
+
+	record = (struct efi_smbios_type1_record *)efi_get_smbios_record(1);
+	if (!record)
+		return false;
+
+	product = efi_get_smbios_string(record, product_name);
+	if (!product)
+		return false;
+
+	for (int i = 0; i < ARRAY_SIZE(type1_product_matches); i++) {
+		if (!strcmp(product, type1_product_matches[i]))
+			return true;
+	}
+
+	return false;
+}
+
+static void apple_set_os(void)
+{
+	struct {
+		unsigned long version;
+		efi_status_t (__efiapi *set_os_version)(const char *);
+		efi_status_t (__efiapi *set_os_vendor)(const char *);
+	} *set_os;
+	efi_status_t status;
+
+	if (!efi_is_64bit() || !apple_match_product_name())
+		return;
+
+	status = efi_bs_call(locate_protocol, &APPLE_SET_OS_PROTOCOL_GUID, NULL,
+			     (void **)&set_os);
+	if (status != EFI_SUCCESS)
+		return;
+
+	if (set_os->version >= 2) {
+		status = set_os->set_os_vendor("Apple Inc.");
+		if (status != EFI_SUCCESS)
+			efi_err("Failed to set OS vendor via apple_set_os\n");
+	}
+
+	if (set_os->version > 0) {
+		/* The version being set doesn't seem to matter */
+		status = set_os->set_os_version("Mac OS X 10.9");
+		if (status != EFI_SUCCESS)
+			efi_err("Failed to set OS version via apple_set_os\n");
+	}
+}
+
 efi_status_t efi_adjust_memory_range_protection(unsigned long start,
 						unsigned long size)
 {
@@ -335,9 +397,12 @@ static const efi_char16_t apple[] = L"Apple";
 
 static void setup_quirks(struct boot_params *boot_params)
 {
-	if (IS_ENABLED(CONFIG_APPLE_PROPERTIES) &&
-	    !memcmp(efistub_fw_vendor(), apple, sizeof(apple)))
-		retrieve_apple_device_properties(boot_params);
+	if (!memcmp(efistub_fw_vendor(), apple, sizeof(apple))) {
+		if (IS_ENABLED(CONFIG_APPLE_PROPERTIES))
+			retrieve_apple_device_properties(boot_params);
+
+		apple_set_os();
+	}
 }
 
 /*

include/linux/efi.h

@@ -385,6 +385,7 @@ void efi_native_runtime_setup(void);
 #define EFI_MEMORY_ATTRIBUTES_TABLE_GUID	EFI_GUID(0xdcfa911d, 0x26eb, 0x469f,  0xa2, 0x20, 0x38, 0xb7, 0xdc, 0x46, 0x12, 0x20)
 #define EFI_CONSOLE_OUT_DEVICE_GUID		EFI_GUID(0xd3b36f2c, 0xd551, 0x11d4,  0x9a, 0x46, 0x00, 0x90, 0x27, 0x3f, 0xc1, 0x4d)
 #define APPLE_PROPERTIES_PROTOCOL_GUID		EFI_GUID(0x91bd12fe, 0xf6c3, 0x44fb,  0xa5, 0xb7, 0x51, 0x22, 0xab, 0x30, 0x3a, 0xe0)
+#define APPLE_SET_OS_PROTOCOL_GUID		EFI_GUID(0xc5c5da95, 0x7d5c, 0x45e6,  0xb2, 0xf1, 0x3f, 0xd5, 0x2b, 0xb1, 0x00, 0x77)
 #define EFI_TCG2_PROTOCOL_GUID			EFI_GUID(0x607f766c, 0x7455, 0x42be,  0x93, 0x0b, 0xe4, 0xd7, 0x6d, 0xb2, 0x72, 0x0f)
 #define EFI_TCG2_FINAL_EVENTS_TABLE_GUID	EFI_GUID(0x1e2ed096, 0x30e2, 0x4254,  0xbd, 0x89, 0x86, 0x3b, 0xbe, 0xf8, 0x23, 0x25)
 #define EFI_LOAD_FILE_PROTOCOL_GUID		EFI_GUID(0x56ec3091, 0x954c, 0x11d2,  0x8e, 0x3f, 0x00, 0xa0, 0xc9, 0x69, 0x72, 0x3b)