Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Subject: Re: [tip:x86/urgent] x86/apic: Fix signedness bug in APIC ID validity
 checks
To:     <peterz@infradead.org>, <lirongqing@baidu.com>,
        <linux-kernel@vger.kernel.org>, <mingo@kernel.org>,
        <hpa@zytor.com>, <tglx@linutronix.de>,
        <linux-tip-commits@vger.kernel.org>
References: <1523322966-10296-1-git-send-email-lirongqing@baidu.com>
 <tip-a774635db5c430cbf21fa5d2f2df3d23aaa8e782@git.kernel.org>
From:   Dou Liyang <douly.fnst@cn.fujitsu.com>
Message-ID: <e66e1b1d-a8d0-ce74-f3c6-4bdc4432efb7@cn.fujitsu.com>
Date:   Wed, 11 Apr 2018 15:01:54 +0800
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101
 Thunderbird/52.5.2
MIME-Version: 1.0
In-Reply-To: <tip-a774635db5c430cbf21fa5d2f2df3d23aaa8e782@git.kernel.org>
Content-Type: text/plain; charset="utf-8"; format=flowed
Content-Language: en-US
Content-Transfer-Encoding: 8bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Hi Thomas,

At 04/10/2018 10:51 PM, tip-bot for Li RongQing wrote:
[...]

> x86/apic: Fix signedness bug in APIC ID validity checks
> 
> The APIC ID as parsed from ACPI MADT is validity checked with the
> apic->apic_id_valid() callback, which depends on the selected APIC type.
> 
> For non X2APIC types APIC IDs >= 0xFF are invalid, but values > 0x7FFFFFFF

Today when I am reading "Intel® 64 Architecture x2APIC Specification", I
find that below in chapter 2.4.1:

   The APIC ID value of FFFF_FFFFH and the highest value corresponding to
   the imple-mented bit-width of the local APIC ID register in the system
   are reserved and cannot be assigned to any logical processor.

Seems, FFFF_FFFFH is also invalid for X2APIC types, Shall we also do the
validity check for X2APIC ID?

acpi_parse_x2apic()
	...
	/* Ignore invalid ID */
	if (apic_id == 0xffffffff)
		return 0;
	...

Thanks,
	dou