On Friday, June 19, 2015 11:38:28 AM Lv Zheng wrote: > ACPICA commit 7aa598d711644ab0de5f70ad88f1e2de253115e4 > > The root cause of the reported bug might be one of the followings: > 1. BIOS may favor the 64-bit firmware waking vector address when the > version of the FACS is greater than 0 and Linux currently only supports > resuming from the real mode, so the 64-bit firmware waking vector has > never been set and might be invalid to BIOS while the commit enables > higher version FACS. > 2. BIOS may favor the FACS reported via the "FIRMWARE_CTRL" field in the > FADT while the commit doesn't set the firmware waking vector address of > the FACS reported by "FIRMWARE_CTRL", it only sets the firware waking > vector address of the FACS reported by "X_FIRMWARE_CTRL". > > This patch excludes the cases that can trigger the bugs caused by the root > cause 1. > > ACPI specification says: > A. 32-bit FACS address (FIRMWARE_CTRL field in FADT): > Physical memory address of the FACS, where OSPM and firmware exchange > control information. > If the X_FIRMWARE_CTRL field contains a non zero value then this field > must be zero. > A zero value indicates that no FACS is specified by this field. > B. 64-bit FACS address (X_FIRMWARE_CTRL field in FADT): > 64bit physical memory address of the FACS. > This field is used when the physical address of the FACS is above 4GB. > If the FIRMWARE_CTRL field contains a non zero value then this field > must be zero. > A zero value indicates that no FACS is specified by this field. > Thus the 32bit and 64bit firmware waking vector should indicate completely > different resuming environment - real mode (1MB addressable) and non real > mode (4GB+ addressable) and currently Linux only supports resuming from > real mode. > > This patch enables 64-bit firmware waking vector for selected FACS via > acpi_set_firmware_waking_vector() so that it's up to OSPMs to determine which > resuming mode should be used by BIOS and ACPICA changes won't trigger the > bugs caused by the root cause 1. For example, Linux can pass > physical_address64=0 as the parameter of acpi_set_firmware_waking_vector() to > indicate no 64bit waking vector support. Lv Zheng. > > Link: https://bugzilla.kernel.org/show_bug.cgi?id=74021 > Link: https://github.com/acpica/acpica/commit/7aa598d7 > Reported-and-tested-by: Oswald Buddenhagen <ossi@xxxxxxx> > Signed-off-by: Lv Zheng <lv.zheng@xxxxxxxxx> > Signed-off-by: Bob Moore <robert.moore@xxxxxxxxx> So what the patch does is to replace two functions, acpi_set_firmware_waking_vector() taking one u32 argument and acpi_set_firmware_waking_vector64() taking one u64 argument, with a modified acpi_set_firmware_waking_vector() taking two arguments of type acpi_physical_address. And it breaks compliation when applied to Linux as is AFAICS, doesn't it? I guess the point is to allow the OS to set firmware_waking_vector *and* clear xfirmware_waking_vector at the same time (by passing 0 as the second argument of the function). And that helps to address the issue when xfirmware_waking_vector has a random value to start with, we don't clear it and the BIOS thinks it is OK to use it, right? If that's the case, this patch should be combined with [4/32] and the signal-to-noise ratio of [4/32] needs to be increased quite a bit. Rafael -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
