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Date: Sun, 15 Aug 2010 12:30:57 +0400
From: Cyrill Gorcunov <gorcunov@gmail.com>
To: Yinghai Lu <yinghai@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>,
        "H. Peter Anvin" <hpa@zytor.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        linux-kernel@vger.kernel.org,
        Suresh Siddha <suresh.b.siddha@intel.com>,
        "Eric W. Biederman" <ebiederm@xmission.com>
Subject: Re: [PATCH] x86: Don't write io_apic ID if it is not changed
Message-ID: <20100815083057.GB5629@lenovo>
References: <4C66FEA9.3040303@kernel.org> <20100815082446.GA5629@lenovo>
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On Sun, Aug 15, 2010 at 12:24:46PM +0400, Cyrill Gorcunov wrote:
...
> As far as I see, this was done by a purpose in former code. Consider the
> situation when mp_ioapics[apic_id].apicid >= get_physical_broadcast().
> By code flow (io_apic.c:2099) this set
> 
> 		if (mp_ioapics[apic_id].apicid >= get_physical_broadcast()) {
> 			printk(KERN_ERR "BIOS bug, IO-APIC#%d ID is %d in the MPC table!...\n",
> 				apic_id, mp_ioapics[apic_id].apicid);
> 			printk(KERN_ERR "... fixing up to %d. (tell your hw vendor)\n",
> 				reg_00.bits.ID);
> --->			mp_ioapics[apic_id].apicid = reg_00.bits.ID;
> 		}
> 
> So with your patch we always hit "continue" without real changing of ID which
> is not correct.
> 
> But perhaps I miss something?
> 
> 	-- Cyrill

False alarm Yinghai, of course there is no need to write same value back,
sorry for noise.

	-- Cyrill