linux-kernel - Re: [GIT PULL] x86/apic updates for v3.20

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Date:	Sat, 14 Feb 2015 01:47:23 +0800
From:	Jiang Liu <jiang.liu@...ux.intel.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Joerg Roedel <joro@...tes.org>
CC:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Ingo Molnar <mingo@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [GIT PULL] x86/apic updates for v3.20



On 2015/2/14 1:00, Linus Torvalds wrote:
> On Fri, Feb 13, 2015 at 7:47 AM, Joerg Roedel <joro@...tes.org> wrote:
>>
>> So the condition should rather look like this to keep x2apic disabled
>> like before:
> 
> Yes, this works for me too.
> 
>> diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
>> index b665d24..770a0bb 100644
>> --- a/arch/x86/kernel/apic/apic.c
>> +++ b/arch/x86/kernel/apic/apic.c
>> @@ -1580,8 +1580,8 @@ static __init void try_to_enable_x2apic(int remap_mode)
>>                  * under KVM
>>                  */
>>                 if (max_physical_apicid > 255 ||
>> -                   (IS_ENABLED(CONFIG_HYPERVISOR_GUEST) &&
>> -                    !hypervisor_x2apic_available())) {
>> +                   !(IS_ENABLED(CONFIG_HYPERVISOR_GUEST) &&
>> +                     hypervisor_x2apic_available())) {
>>                         pr_info("x2apic: IRQ remapping doesn't support X2APIC mode\n");
>>                         x2apic_disable();
>>                         return;
>>
>> Another solution would be to just revert 5fcee53ce705. This code is not
>> in any fast-path, so we can live well without that optimization.
> 
> Jiang, preferences? Revert, or fix like the above?
Hi Linus,
	I think reverting is better.
	The IS_ENABLED(CONFIG_HYPERVISOR_GUEST) optimization doesn't
give us much, but it makes the code a little complex.
Regards!
Gerry

> 
>                      Linus
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