linux-kernel - Re: [PATCH linux v2] xen: change the type of xen_vcpu_id to uint32

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Date:	Fri, 29 Jul 2016 10:13:27 -0700 (PDT)
From:	Stefano Stabellini <sstabellini@...nel.org>
To:	Vitaly Kuznetsov <vkuznets@...hat.com>
cc:	xen-devel@...ts.xenproject.org, linux-kernel@...r.kernel.org,
	Boris Ostrovsky <boris.ostrovsky@...cle.com>,
	David Vrabel <david.vrabel@...rix.com>,
	Juergen Gross <jgross@...e.com>,
	Stefano Stabellini <sstabellini@...nel.org>,
	Julien Grall <julien.grall@....com>
Subject: Re: [PATCH linux v2] xen: change the type of xen_vcpu_id to
 uint32_t

On Fri, 29 Jul 2016, Vitaly Kuznetsov wrote:
> We pass xen_vcpu_id mapping information to hypercalls which require
> uint32_t type so it would be cleaner to have it as uint32_t. The
> initializer to -1 can be dropped as we always do the mapping before using
> it and we never check the 'not set' value anyway.
> 
> Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>

It would probably be better to keep the initializer and add an assert to
xen_vcpu_nr. But I don't want to be too picky, so:

Reviewed-by: Stefano Stabellini <sstabellini@...nel.org>


> Changes since v2:
> - Change the return value type of xen_vcpu_nr to uint32_t [David Vrabel]
> ---
>  arch/arm/xen/enlighten.c | 2 +-
>  arch/x86/xen/enlighten.c | 2 +-
>  include/xen/xen-ops.h    | 4 ++--
>  3 files changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c
> index 6d3a171..1752116 100644
> --- a/arch/arm/xen/enlighten.c
> +++ b/arch/arm/xen/enlighten.c
> @@ -47,7 +47,7 @@ DEFINE_PER_CPU(struct vcpu_info *, xen_vcpu);
>  static struct vcpu_info __percpu *xen_vcpu_info;
>  
>  /* Linux <-> Xen vCPU id mapping */
> -DEFINE_PER_CPU(int, xen_vcpu_id) = -1;
> +DEFINE_PER_CPU(uint32_t, xen_vcpu_id);
>  EXPORT_PER_CPU_SYMBOL(xen_vcpu_id);
>  
>  /* These are unused until we support booting "pre-ballooned" */
> diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
> index 54eef1a..78a14a0 100644
> --- a/arch/x86/xen/enlighten.c
> +++ b/arch/x86/xen/enlighten.c
> @@ -120,7 +120,7 @@ DEFINE_PER_CPU(struct vcpu_info *, xen_vcpu);
>  DEFINE_PER_CPU(struct vcpu_info, xen_vcpu_info);
>  
>  /* Linux <-> Xen vCPU id mapping */
> -DEFINE_PER_CPU(int, xen_vcpu_id) = -1;
> +DEFINE_PER_CPU(uint32_t, xen_vcpu_id);
>  EXPORT_PER_CPU_SYMBOL(xen_vcpu_id);
>  
>  enum xen_domain_type xen_domain_type = XEN_NATIVE;
> diff --git a/include/xen/xen-ops.h b/include/xen/xen-ops.h
> index a4926f1..aac1be8 100644
> --- a/include/xen/xen-ops.h
> +++ b/include/xen/xen-ops.h
> @@ -9,8 +9,8 @@
>  
>  DECLARE_PER_CPU(struct vcpu_info *, xen_vcpu);
>  
> -DECLARE_PER_CPU(int, xen_vcpu_id);
> -static inline int xen_vcpu_nr(int cpu)
> +DECLARE_PER_CPU(uint32_t, xen_vcpu_id);
> +static inline uint32_t xen_vcpu_nr(int cpu)
>  {
>  	return per_cpu(xen_vcpu_id, cpu);
>  }
> -- 
> 2.7.4
>