linux-kernel - RE: [PATCH 2/7] x86/hyper-v: fast hypercall implementation

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Date:   Fri, 7 Apr 2017 19:42:10 +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 2/7] x86/hyper-v: fast hypercall implementation

> -----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 2/7] x86/hyper-v: fast hypercall implementation
 
> diff --git a/arch/x86/include/asm/mshyperv.h
> b/arch/x86/include/asm/mshyperv.h index 331e834..9a5f58b 100644
> --- a/arch/x86/include/asm/mshyperv.h
> +++ b/arch/x86/include/asm/mshyperv.h
> @@ -216,6 +216,43 @@ static inline u64 hv_do_hypercall(u64 control, void
> *input, void *output)  #endif /* !x86_64 */  }
> 
> +/* Fast hypercall with 8 bytes of input and no output */ static inline
> +u64 hv_do_fast_hypercall8(u16 code, u64 input1) {
> +	union hv_hypercall_input control = {0};
> +
> +	control.code = code;
> +	control.fast = 1;
> +#ifdef CONFIG_X86_64
> +	{
> +		u64 hv_status;
> +
> +		__asm__ __volatile__("call *%3"
> +				     : "=a" (hv_status)
> +				     : "c" (control.as_uint64), "d" (input1),
> +				       "m" (hv_hypercall_pg)
> +				     : "cc", "r8", "%r9", "%r10", "%r11");
> +		return hv_status;
Clobber memory (are there such fast hypercalls)?

> +	}
> +#else
> +	{
> +		u32 hv_status_hi, hv_status_lo;
> +
> +		__asm__ __volatile__ ("call *%6"
> +				      : "=d"(hv_status_hi),
> +					"=a"(hv_status_lo) :
> +					"d" (control.as_uint32_hi),
> +					"a" (control.as_uint32_lo),
> +					"c" ((u32)input1),
> +					"b" ((u32)(input1 >> 32)),
> +					"m" (hv_hypercall_pg)
> +				      : "cc");
> +
> +		return hv_status_lo | ((u64)hv_status_hi << 32);
> +	}
> +#endif
Please clobber ECX, EDI and ESI for x86. Clobber memory as well?