linux-kernel - Re: [PATCH 1/2] x86/entry: Avoid interrupt flag save and restore

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Date:	Mon, 6 Jun 2016 17:47:52 +0200
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...nel.org.com>,
	"H. Peter Anvin" <hpa@...or.com>, X86 ML <x86@...nel.org>,
	Rik van Riel <riel@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH 1/2] x86/entry: Avoid interrupt flag save and restore



On 04/06/2016 07:07, Andy Lutomirski wrote:
> On May 30, 2016 5:30 AM, "Paolo Bonzini" <pbonzini@...hat.com> wrote:
>>
>> Thanks to all the work that was done by Andy Lutomirski and others,
>> enter_from_user_mode and prepare_exit_to_usermode are now called only with
>> interrupts disabled.  Let's provide them a version of user_enter/user_exit
>> that skips saving and restoring the interrupt flag.
> 
>> +/* Called with interrupts disabled.  */
>> +static inline void __user_enter(void)
>> +{
>> +       if (context_tracking_is_enabled())
>> +               __context_tracking_enter(CONTEXT_USER);
>> +
>> +}
> 
> Would user_enter_irqs_off be a better name?

I'm just mimicking __context_tracking_enter and vs.
context_tracking_enter.  So it is at least consistent with those functions.

The guest ones are not quite as consistent.  I can fix that later,
there's no reason also to have guest context tracking split between
include/linux/context_tracking.h and include/linux/kvm_host.h.

Thanks,

Paolo