linux-kernel - Re: [PATCH 2/2] x86/apic: check global clockevent in lapic timer setup

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <4B2AB1F0.1020105@linux.intel.com>
Date:	Thu, 17 Dec 2009 14:34:24 -0800
From:	"H. Peter Anvin" <hpa@...ux.intel.com>
To:	"Pan, Jacob jun" <jacob.jun.pan@...el.com>
CC:	Cyrill Gorcunov <gorcunov@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"x86@...nel.org" <x86@...nel.org>
Subject: Re: [PATCH 2/2] x86/apic: check global clockevent in lapic timer
 setup

On 12/17/2009 02:31 PM, Pan, Jacob jun wrote:
>> Wouldn't be better to operate the same way as in case of "noapictimer"
>> boot option. I guess the non-pc x86 midplatforms you're mentioning
>> do not use SMP ever but just to be consistent in code.
>>
> [[JPAN]] We do use SMP with hyper threading in Moorestown.
> In that case we have a per cpu platform timer without global clockevent.
> so i think we don't want the dummy lapic event. we don't want to use the
> broadcast mechanism as mentioned in the comments before disabling lapic
> timer.
> 
> For moorestown, I can use x86_init.timers.setup_percpu_clockev
> abstraction function so that Moorestown platform does not need to call
> setup_boot_APIC_clock() if per cpu platform timer is used. so many IFs :).
> 
> But in the case of having constant and always on LAPIC timer, we still do
> not want the dummy lapic clockevent and the broadcast. we will just have
> per cpu always on local apic timers without global clockevent device.

OK, I'm not entirely sure I follow this, and I'm not sure someone trying
to understand the code in five years would, either.  I don't really see
the above translating into "we don't have a global clockevent, therefore
we shouldn't initialize (but should still not disable) the local APIC
timer."

	-hpa
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/