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Commit 10daf10a authored by Dou Liyang's avatar Dou Liyang Committed by Thomas Gleixner
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x86/acpi: Prevent X2APIC id 0xffffffff from being accounted 



RongQing reported that there are some X2APIC id 0xffffffff in his machine's
ACPI MADT table, which makes the number of possible CPU inaccurate.

The reason is that the ACPI X2APIC parser has no sanity check for APIC ID
0xffffffff, which is an invalid id in all APIC types. See "Intel® 64
Architecture x2APIC Specification", Chapter 2.4.1.

Add a sanity check to acpi_parse_x2apic() which ignores the invalid id.

Reported-by: default avatarLi RongQing <lirongqing@baidu.com>
Signed-off-by: default avatarDou Liyang <douly.fnst@cn.fujitsu.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Cc: len.brown@intel.com
Cc: rjw@rjwysocki.net
Cc: hpa@zytor.com
Link: https://lkml.kernel.org/r/20180412014052.25186-1-douly.fnst@cn.fujitsu.com
parent d3878e16

arch/x86/kernel/acpi/boot.c

+4 −0
Original line number Diff line number Diff line
@@ -215,6 +215,10 @@ acpi_parse_x2apic(struct acpi_subtable_header *header, const unsigned long end) 
	apic_id = processor->local_apic_id;

	enabled = processor->lapic_flags & ACPI_MADT_ENABLED;



	/* Ignore invalid ID */

	if (apic_id == 0xffffffff)

		return 0;



	/*

	 * We need to register disabled CPU as well to permit

	 * counting disabled CPUs. This allows us to size