From: "H. Peter Anvin" <hpa@zytor.com>
To: Yinghai Lu <yinghai@kernel.org>
Cc: "Zhang, Lin-Bao (Linux Kernel R&D)" <linbao.zhang@hp.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"alan@lxorguk.ukuu.org.uk" <alan@lxorguk.ukuu.org.uk>,
"mingo@redhat.com" <mingo@redhat.com>,
"tglx@linutronix.de" <tglx@linutronix.de>,
"x86@kernel.org" <x86@kernel.org>,
"a.p.zijlstra@chello.nl" <a.p.zijlstra@chello.nl>,
"jarkko.sakkinen@intel.com" <jarkko.sakkinen@intel.com>,
"joerg.roedel@amd.com" <joerg.roedel@amd.com>,
"agordeev@redhat.com" <agordeev@redhat.com>
Subject: Re: Why Linux kernel forced to enter X2APIC mode( just because of booting cpu has supported x2apic) without depending on BIOS' setting in MSR->x2apic enablement bit ?
Date: Thu, 20 Dec 2012 08:48:31 -0800 [thread overview]
Message-ID: <50D3415F.8010205@zytor.com> (raw)
In-Reply-To: <CAE9FiQVRcGvaTJ6NrxnQuFbPT9OwB7j8xxhDe5kcYUpgAMkz1A@mail.gmail.com>
On 12/20/2012 08:46 AM, Yinghai Lu wrote:
> On Thu, Dec 20, 2012 at 2:38 AM, Zhang, Lin-Bao (Linux Kernel R&D)
> <linbao.zhang@hp.com> wrote:
>> I think current core argument is our BIOS did following judgement ,
>> but Linux kernel did not(Linux seems just judge BSP supports x2apic mode or not by CPUID method)
>
> kernel checks that, if the BSP in x2apic mode, kernel will check if
> intr-remapping can be enabled, otherwise
> it will switch back to xapic mode.
>
>> Our BSP really supports x2apic mode, however,as this spec, our BIOS think some of configuration of server
>> could not meet x2apic conditions ,So didn't place local xAPICs into x2apic mode.
>> But linux kernel indeed enable x2apic mode(just believe BSP, didn't do above judgement) . so this is the conflict.
>
> so your BIOS is wrong, it does not enable intr-remapping.
>
FWIW, I bought a *server* today and it didn't have interrupt remapping
and x2APIC, I would consider it defective and return it.
-hpa
next prev parent reply other threads:[~2012-12-20 16:49 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-12-18 9:50 Why Linux kernel forced to enter X2APIC mode( just because of booting cpu has supported x2apic) without depending on BIOS' setting in MSR->x2apic enablement bit ? Zhang, Lin-Bao (Linux Kernel R&D)
2012-12-18 17:49 ` Yinghai Lu
2012-12-19 10:13 ` Zhang, Lin-Bao (Linux Kernel R&D)
2012-12-19 16:03 ` Yinghai Lu
2012-12-19 10:36 ` Zhang, Lin-Bao (Linux Kernel R&D)
2012-12-19 16:05 ` Yinghai Lu
2012-12-20 10:38 ` Zhang, Lin-Bao (Linux Kernel R&D)
2012-12-20 16:46 ` Yinghai Lu
2012-12-20 16:48 ` H. Peter Anvin [this message]
2012-12-19 16:10 ` H. Peter Anvin
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