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Commit 5b53496a authored by Zhao Yakui's avatar Zhao Yakui Committed by Andi Kleen
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ACPI: Disable the C2C3_FFH access mode HW has no MWAIT support 



991528d7
(ACPI: Processor native C-states using MWAIT)
started passing C2C3_FFH to _PDC to tell the BIOS
that Linux supports MWAIT for deep C-states.

However, we should first double check with the hardware
that it actually supports MWAIT before potentially exposing
a BIOS bug of an MWAIT _CST on HW that doesn't support MWAIT.

Signed-off-by: default avatarZhao Yakui <yakui.zhao@intel.com>
Signed-off-by: default avatarLi Shaohua <shaohua.li@intel.com>
Signed-off-by: default avatarLen Brown <len.brown@intel.com>
Signed-off-by: default avatarAndi Kleen <ak@linux.intel.com>
parent 71b58cbb

arch/x86/kernel/acpi/processor.c

+6 −0
Original line number Diff line number Diff line
@@ -56,6 +56,12 @@ static void init_intel_pdc(struct acpi_processor *pr, struct cpuinfo_x86 *c) 
	if (cpu_has(c, X86_FEATURE_ACPI))

		buf[2] |= ACPI_PDC_T_FFH;



	/*

	 * If mwait/monitor is unsupported, C2/C3_FFH will be disabled

	 */

	if (!cpu_has(c, X86_FEATURE_MWAIT))

		buf[2] &= ~(ACPI_PDC_C_C2C3_FFH);



	obj->type = ACPI_TYPE_BUFFER;

	obj->buffer.length = 12;

	obj->buffer.pointer = (u8 *) buf;