linux-kernel - RE: [PATCH 4/7] x86/hyperv: implement rep hypercalls

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Message-ID: <MWHPR21MB06393B2E4FA3DE9EACCEA2EFF10C0@MWHPR21MB0639.namprd21.prod.outlook.com>
Date:   Fri, 7 Apr 2017 19:48:06 +0000
From:   Jork Loeser <Jork.Loeser@...rosoft.com>
To:     Vitaly Kuznetsov <vkuznets@...hat.com>,
        "devel@...uxdriverproject.org" <devel@...uxdriverproject.org>,
        "x86@...nel.org" <x86@...nel.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "KY Srinivasan" <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Steven Rostedt <rostedt@...dmis.org>
Subject: RE: [PATCH 4/7] x86/hyperv: implement rep hypercalls

> -----Original Message-----
> From: Vitaly Kuznetsov [mailto:vkuznets@...hat.com]
> Sent: Friday, April 7, 2017 04:27
> To: devel@...uxdriverproject.org; x86@...nel.org
> Cc: linux-kernel@...r.kernel.org; KY Srinivasan <kys@...rosoft.com>;
> Haiyang Zhang <haiyangz@...rosoft.com>; Stephen Hemminger
> <sthemmin@...rosoft.com>; Thomas Gleixner <tglx@...utronix.de>; Ingo
> Molnar <mingo@...hat.com>; H. Peter Anvin <hpa@...or.com>; Steven
> Rostedt <rostedt@...dmis.org>; Jork Loeser <Jork.Loeser@...rosoft.com>
> Subject: [PATCH 4/7] x86/hyperv: implement rep hypercalls
 
> diff --git a/arch/x86/include/asm/mshyperv.h
> b/arch/x86/include/asm/mshyperv.h index 9a5f58b..a2c996b 100644
> --- a/arch/x86/include/asm/mshyperv.h
> +++ b/arch/x86/include/asm/mshyperv.h
> @@ -4,6 +4,7 @@
>  #include <linux/types.h>
>  #include <linux/interrupt.h>
>  #include <linux/clocksource.h>
> +#include <linux/nmi.h>
>  #include <asm/hyperv.h>
> 
>  /*
> @@ -253,6 +254,26 @@ static inline u64 hv_do_fast_hypercall8(u16 code,
> u64 input1)  #endif  }
> 
> +static inline u64 hv_do_rep_hypercall(u16 code, u16 rep_count, void
> *input,
> +				      void *output)
> +{
> +	union hv_hypercall_input hc_input = { .code = code,
> +					      .rep_count = rep_count};

Is there a way to statically verify the re-count not to exceed 12 bits? Could a dynamic check be justified? Perhaps a function comment?