linux-kernel - Re: [PATCH v6 01/11] x86/paravirt: Move halt paravirt calls under CONFIG

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Date:   Fri, 3 Sep 2021 12:03:56 -0700
From:   "Kuppuswamy, Sathyanarayanan" 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
        Paolo Bonzini <pbonzini@...hat.com>,
        Juergen Gross <jgross@...e.com>, Deep Shah <sdeep@...are.com>,
        VMware Inc <pv-drivers@...are.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, Peter H Anvin <hpa@...or.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Tony Luck <tony.luck@...el.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Kirill Shutemov <kirill.shutemov@...ux.intel.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Kuppuswamy Sathyanarayanan <knsathya@...nel.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 01/11] x86/paravirt: Move halt paravirt calls under
 CONFIG_PARAVIRT



On 9/3/21 11:22 AM, Borislav Petkov wrote:
> On Fri, Sep 03, 2021 at 10:28:02AM -0700, Kuppuswamy Sathyanarayanan wrote:
>> diff --git a/arch/x86/include/asm/irqflags.h b/arch/x86/include/asm/irqflags.h
>> index c5ce9845c999..ddc77c95adc6 100644
>> --- a/arch/x86/include/asm/irqflags.h
>> +++ b/arch/x86/include/asm/irqflags.h
>> @@ -59,27 +59,8 @@ static inline __cpuidle void native_halt(void)
>>   
>>   #endif
>>   
>> -#ifdef CONFIG_PARAVIRT_XXL
>> -#include <asm/paravirt.h>
>> -#else
>> +#ifndef CONFIG_PARAVIRT
>>   #ifndef __ASSEMBLY__
>> -#include <linux/types.h>
>> -
>> -static __always_inline unsigned long arch_local_save_flags(void)
>> -{
>> -	return native_save_fl();
>> -}
>> -
>> -static __always_inline void arch_local_irq_disable(void)
>> -{
>> -	native_irq_disable();
>> -}
>> -
>> -static __always_inline void arch_local_irq_enable(void)
>> -{
>> -	native_irq_enable();
>> -}
>> -
>>   /*
>>    * Used in the idle loop; sti takes one instruction cycle
>>    * to complete:
>> @@ -97,6 +78,33 @@ static inline __cpuidle void halt(void)
>>   {
>>   	native_halt();
>>   }
>> +#endif /* __ASSEMBLY__ */
>> +#endif /* CONFIG_PARAVIRT */
>> +
>> +#ifdef CONFIG_PARAVIRT
>> +#ifndef __ASSEMBLY__
>> +#include <asm/paravirt.h>
>> +#endif /* __ASSEMBLY__ */
>> +#endif /* CONFIG_PARAVIRT */
> 
> I think the way we write those is like this:
> 
> #ifdef CONFIG_PARAVIRT
> 
> # ifndef __ASSEMBLY__
> # include <asm/paravirt.h>
> # endif
> 
> #else /* ! CONFIG_PARAVIRT */
> 
> # ifndef __ASSEMBLY__
> /*
>   * Used in the idle loop; sti takes one instruction cycle
>   * to complete:
>   */
> static inline __cpuidle void arch_safe_halt(void)
> {
> 	native_safe_halt();
> }
> 
> /*
>   * Used when interrupts are already enabled or to
>   * shutdown the processor:
>   */
> static inline __cpuidle void halt(void)
> {
> 	native_halt();
> }
> # endif /* __ASSEMBLY__ */
> 
> #endif /* CONFIG_PARAVIRT */

Yes, I can combine the #ifdef as you have mentioned. I can fix this
in next version.

> 
> Note the empty space after the '#' of the inner ifdef to show that it is
> an inner one.

Is this new convention? #ifdefs used in this file does not follow this
format.

-- 
Sathyanarayanan Kuppuswamy
Linux Kernel Developer