diff options
| author | Jan Engelhardt | 2020-03-05 13:24:25 +0100 |
|---|---|---|
| committer | Rafael J. Wysocki | 2020-03-14 10:41:56 +0100 |
| commit | ecb9c790999fd6c5af0f44783bd0217f0b89ec2b (patch) | |
| tree | 3a100d2acdbba78c5e39c49649b2195ebfcf7f4b | |
| parent | 1ffb8d032d03d686e3b06378780944608cc77906 (diff) | |
acpi/x86: ignore unspecified bit positions in the ACPI global lock field
The value in "new" is constructed from "old" such that all bits defined
as reserved by the ACPI spec[1] are left untouched. But if those bits
do not happen to be all zero, "new < 3" will not evaluate to true.
The firmware of the laptop(s) Medion MD63490 / Akoya P15648 comes with
garbage inside the "FACS" ACPI table. The starting value is
old=0x4944454d, therefore new=0x4944454e, which is >= 3. Mask off
the reserved bits.
[1] https://uefi.org/sites/default/files/resources/ACPI_6_2.pdf
Link: https://bugzilla.kernel.org/show_bug.cgi?id=206553
Cc: All applicable <stable@vger.kernel.org>
Signed-off-by: Jan Engelhardt <jengelh@inai.de>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
| -rw-r--r-- | arch/x86/kernel/acpi/boot.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c index d1757ceca8ae..1ae5439a9a85 100644 --- a/arch/x86/kernel/acpi/boot.c +++ b/arch/x86/kernel/acpi/boot.c @@ -1748,7 +1748,7 @@ int __acpi_acquire_global_lock(unsigned int *lock) new = (((old & ~0x3) + 2) + ((old >> 1) & 0x1)); val = cmpxchg(lock, old, new); } while (unlikely (val != old)); - return (new < 3) ? -1 : 0; + return ((new & 0x3) < 3) ? -1 : 0; } int __acpi_release_global_lock(unsigned int *lock) |