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

From: Jork Loeser
Date: Fri Apr 07 2017 - 15:42:29 EST


> -----Original Message-----
> From: Vitaly Kuznetsov [mailto:vkuznets@xxxxxxxxxx]
> Sent: Friday, April 7, 2017 04:27
> To: devel@xxxxxxxxxxxxxxxxxxxxxx; x86@xxxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx; KY Srinivasan <kys@xxxxxxxxxxxxx>;
> Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>; Stephen Hemminger
> <sthemmin@xxxxxxxxxxxxx>; Thomas Gleixner <tglx@xxxxxxxxxxxxx>; Ingo
> Molnar <mingo@xxxxxxxxxx>; H. Peter Anvin <hpa@xxxxxxxxx>; Steven
> Rostedt <rostedt@xxxxxxxxxxx>; Jork Loeser <Jork.Loeser@xxxxxxxxxxxxx>
> 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?