linux-kernel - Re: x2apic boot failure on recent sandy bridge system

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Date:	Mon, 12 Dec 2011 17:29:59 -0800
From:	Yinghai Lu <yinghai@...nel.org>
To:	Suresh Siddha <suresh.b.siddha@...el.com>
Cc:	"Berck E. Nash" <flyboy@...il.com>, Ingo Molnar <mingo@...e.hu>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: x2apic boot failure on recent sandy bridge system

On Mon, Dec 12, 2011 at 4:25 PM, Suresh Siddha
<suresh.b.siddha@...el.com> wrote:
> On Mon, 2011-12-12 at 15:21 -0800, Berck E. Nash wrote:
>> On 12/11/2011 08:40 PM, Yinghai Lu wrote:
>> > x2apic pre-enabled skip the mapping for lapic address. so need map it
>> > after fall back.
>> >
>> > please check attached -v5..
>>
>> It appears to work correctly as far as I can tell.
>
> Ok. In this case, it looks like bios didn't enable interrupt-remapping
> (part of vt-d) and just enabled x2apic with out touching or exporting
> vt-d HW.
>
> Yinghai, In other scenarios where OS can't recover, mostly likely we
> will fail in check_timer() when we fall back to xapic. Can we add a
> printk in this case to convey the potential reason (that I mentioned in
> the previous e-mail), so that the user can get more accurate information
> for the check timer failure.

agree. in that case, will have problem.

but i don't think bios buy can go that far to enable intr-remapping
without providing DMAR.

will check if can add print out in check_timer() when
x2apic_preenabled == 1 and x2apic == 0...

Thanks

Yinghai Lu
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