linux-kernel - Re: [Xen-devel] [PATCH 8/9] x86/rtc: replace paravirt

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Date:	Fri, 19 Feb 2016 14:22:12 +0100
From:	Juergen Gross <jgross@...e.com>
To:	"Luis R. Rodriguez" <mcgrof@...nel.org>, bp@...en8.de
Cc:	rusty@...tcorp.com.au, x86@...nel.org,
	linux-kernel@...r.kernel.org, luto@...capital.net,
	xen-devel@...ts.xensource.com, david.vrabel@...rix.com,
	boris.ostrovsky@...cle.com
Subject: Re: [Xen-devel] [PATCH 8/9] x86/rtc: replace paravirt_enabled() check
 with subarch check

On 19/02/16 14:08, Luis R. Rodriguez wrote:
> The current check is a super long winded way of asking if this
> is on lguest. The flags is used for legacy features, this is

What about Xen pv-domU? I wouldn't expect those to have PV_SUPPORTED_RTC
set.


Juergen

> likely inspired by the ACPI IA-PC boot architecture flags, where
> as for RTC it annotates No CMOS real-time clock present. I don't
> expect we will be implementing more legacy features, its simply
> pointless so just remove this legacy flag feature thing as well.
> 
> Signed-off-by: Luis R. Rodriguez <mcgrof@...nel.org>
> ---
>  arch/x86/include/asm/paravirt.h       | 6 ------
>  arch/x86/include/asm/paravirt_types.h | 5 -----
>  arch/x86/include/asm/processor.h      | 1 -
>  arch/x86/kernel/rtc.c                 | 3 ++-
>  arch/x86/xen/enlighten.c              | 3 ---
>  5 files changed, 2 insertions(+), 16 deletions(-)
> 
> diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
> index f6192502149e..c261402340e3 100644
> --- a/arch/x86/include/asm/paravirt.h
> +++ b/arch/x86/include/asm/paravirt.h
> @@ -19,12 +19,6 @@ static inline int paravirt_enabled(void)
>  	return pv_info.paravirt_enabled;
>  }
>  
> -static inline int paravirt_has_feature(unsigned int feature)
> -{
> -	WARN_ON_ONCE(!pv_info.paravirt_enabled);
> -	return (pv_info.features & feature);
> -}
> -
>  static inline void load_sp0(struct tss_struct *tss,
>  			     struct thread_struct *thread)
>  {
> diff --git a/arch/x86/include/asm/paravirt_types.h b/arch/x86/include/asm/paravirt_types.h
> index 77db5616a473..2489d6a08e89 100644
> --- a/arch/x86/include/asm/paravirt_types.h
> +++ b/arch/x86/include/asm/paravirt_types.h
> @@ -70,14 +70,9 @@ struct pv_info {
>  #endif
>  
>  	int paravirt_enabled;
> -	unsigned int features;	  /* valid only if paravirt_enabled is set */
>  	const char *name;
>  };
>  
> -#define paravirt_has(x) paravirt_has_feature(PV_SUPPORTED_##x)
> -/* Supported features */
> -#define PV_SUPPORTED_RTC        (1<<0)
> -
>  struct pv_init_ops {
>  	/*
>  	 * Patch may replace one of the defined code sequences with
> diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
> index 20c11d1aa4cc..10f3614265c1 100644
> --- a/arch/x86/include/asm/processor.h
> +++ b/arch/x86/include/asm/processor.h
> @@ -472,7 +472,6 @@ static inline unsigned long current_top_of_stack(void)
>  #else
>  #define __cpuid			native_cpuid
>  #define paravirt_enabled()	0
> -#define paravirt_has(x) 	0
>  
>  static inline void load_sp0(struct tss_struct *tss,
>  			    struct thread_struct *thread)
> diff --git a/arch/x86/kernel/rtc.c b/arch/x86/kernel/rtc.c
> index 4af8d063fb36..8471523ee127 100644
> --- a/arch/x86/kernel/rtc.c
> +++ b/arch/x86/kernel/rtc.c
> @@ -14,6 +14,7 @@
>  #include <asm/time.h>
>  #include <asm/intel-mid.h>
>  #include <asm/rtc.h>
> +#include <asm/setup.h>
>  
>  #ifdef CONFIG_X86_32
>  /*
> @@ -200,7 +201,7 @@ static __init int add_rtc_cmos(void)
>  	}
>  #endif
>  
> -	if (paravirt_enabled() && !paravirt_has(RTC))
> +	if (boot_params.hdr.hardware_subarch == X86_SUBARCH_LGUEST)
>  		return -ENODEV;
>  
>  	platform_device_register(&rtc_device);
> diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
> index 5b3f1c763806..5c06169bce27 100644
> --- a/arch/x86/xen/enlighten.c
> +++ b/arch/x86/xen/enlighten.c
> @@ -1192,7 +1192,6 @@ static const struct pv_info xen_info __initconst = {
>  #ifdef CONFIG_X86_64
>  	.extra_user_64bit_cs = FLAT_USER_CS64,
>  #endif
> -	.features = 0,
>  	.name = "Xen",
>  };
>  
> @@ -1526,8 +1525,6 @@ asmlinkage __visible void __init xen_start_kernel(void)
>  
>  	/* Install Xen paravirt ops */
>  	pv_info = xen_info;
> -	if (xen_initial_domain())
> -		pv_info.features |= PV_SUPPORTED_RTC;
>  	pv_init_ops = xen_init_ops;
>  	if (!xen_pvh_domain()) {
>  		pv_cpu_ops = xen_cpu_ops;
>