Patch "ACPI / osi: Fix an issue that acpi_osi=!* cannot disable ACPICA internal strings" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

ACPI / osi: Fix an issue that acpi_osi=!* cannot disable ACPICA internal strings

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
acpi-osi-fix-an-issue-that-acpi_osi-cannot-disable-acpica-internal-strings.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Lv Zheng <[email protected]>
Date: Tue, 3 May 2016 16:48:20 +0800
Subject: ACPI / osi: Fix an issue that acpi_osi=!* cannot disable ACPICA internal strings

From: Lv Zheng <[email protected]>

commit 30c9bb0d7603e7b3f4d6a0ea231e1cddae020c32 upstream.

The order of the _OSI related functionalities is as follows:

acpi_blacklisted()
acpi_dmi_osi_linux()
acpi_osi_setup()
acpi_osi_setup()
acpi_update_interfaces() if "!*"
<<<<<<<<<<<<<<<<<<<<<<<<
parse_args()

    __setup("acpi_osi=")
      acpi_osi_setup_linux()
        acpi_update_interfaces() if "!*"
        <<<<<<<<<<<<<<<<<<<<<<<<
  acpi_early_init()
    acpi_initialize_subsystem()
      acpi_ut_initialize_interfaces()
      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

acpi_bus_init()
acpi_os_initialize1()
acpi_install_interface_handler(acpi_osi_handler) acpi_osi_setup_late()
acpi_update_interfaces() for "!" >>>>>>>>>>>>>>>>>>>>>>>>
acpi_osi_handler()

Since acpi_osi_setup_linux() can override acpi_dmi_osi_linux(), the command line setting can override the DMI detection. That's why acpi_blacklisted() is put before __setup("acpi_osi=").

Then we can notice the following wrong invocation order. There are acpi_update_interfaces() (marked by <<<<) calls invoked before acpi_ut_initialize_interfaces() (marked by ^^^^). This makes it impossible to use acpi_osi=!* correctly from OSI DMI table or from the command line. The use of acpi_osi=!* is meant to disable both ACPICA (acpi_gbl_supported_interfaces) and Linux specific strings (osi_setup_entries) while the ACPICA part should have stopped working because of the order issue.

This patch fixes this issue by moving acpi_update_interfaces() to where it is invoked for acpi_osi=! (marked by >>>>) as this is ensured to be invoked after acpi_ut_initialize_interfaces() (marked by ^^^^). Linux specific strings are still handled in the original place in order to make the following command line working: acpi_osi=!* acpi_osi="Module Device".

Note that since acpi_osi=!* is meant to further disable linux specific string comparing to the acpi_osi=!, there is no such use case in our bug fixing work and hence there is no one using acpi_osi=!* either from the command line or from the DMI quirks, this issue is just a theoretical issue.

---
 drivers/acpi/osl.c |   16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

@@ -135,7 +135,7 @@ static struct osi_linux {
 	unsigned int	enable:1;
 	unsigned int	dmi:1;
 	unsigned int	cmdline:1;
-	unsigned int	default_disabling:1;
+	u8		default_disabling;
 } osi_linux = {0, 0, 0, 0};
 
 static u32 acpi_osi_handler(acpi_string interface, u32 supported)

@@ -1444,10 +1444,13 @@ void __init acpi_osi_setup(char *str)
 	if (*str == '!') {
 		str++;
 		if (*str == '\0') {
-			osi_linux.default_disabling = 1;
+			/* Do not override acpi_osi=!* */
+			if (!osi_linux.default_disabling)
+				osi_linux.default_disabling =
+					ACPI_DISABLE_ALL_VENDOR_STRINGS;
 			return;
 		} else if (*str == '*') {
-			acpi_update_interfaces(ACPI_DISABLE_ALL_STRINGS);
+			osi_linux.default_disabling = ACPI_DISABLE_ALL_STRINGS;
 			for (i = 0; i < OSI_STRING_ENTRIES_MAX; i++) {
 				osi = &osi_setup_entries[i];
 				osi->enable = false;

@@ -1520,10 +1523,13 @@ static void __init acpi_osi_setup_late(v
 	acpi_status status;
 
 	if (osi_linux.default_disabling) {
-		status = acpi_update_interfaces(ACPI_DISABLE_ALL_VENDOR_STRINGS);
+		status = acpi_update_interfaces(osi_linux.default_disabling);
 
 		if (ACPI_SUCCESS(status))
-			printk(KERN_INFO PREFIX "Disabled all _OSI OS vendors\n");
+			printk(KERN_INFO PREFIX "Disabled all _OSI OS vendors%s\n",
+				osi_linux.default_disabling ==
+				ACPI_DISABLE_ALL_STRINGS ?
+				" and feature groups" : "");
 	}
 
 	for (i = 0; i < OSI_STRING_ENTRIES_MAX; i++) {

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/acpi-osi-fix-an-issue-that-acpi_osi-cannot-disable-acpica-internal-strings.patch