linux-kernel - Re: [PATCH v8 3/5] x86/hyperv: Add an interface to do nested hypercalls

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Date:   Fri, 9 Dec 2022 10:16:31 -0800
From:   Nuno Das Neves <nunodasneves@...ux.microsoft.com>
To:     Jinank Jain <jinankjain@...ux.microsoft.com>,
        jinankjain@...rosoft.com
Cc:     kys@...rosoft.com, haiyangz@...rosoft.com, wei.liu@...nel.org,
        decui@...rosoft.com, tglx@...utronix.de, mingo@...hat.com,
        bp@...en8.de, dave.hansen@...ux.intel.com, x86@...nel.org,
        hpa@...or.com, arnd@...db.de, peterz@...radead.org,
        jpoimboe@...nel.org, seanjc@...gle.com,
        kirill.shutemov@...ux.intel.com, ak@...ux.intel.com,
        sathyanarayanan.kuppuswamy@...ux.intel.com,
        linux-hyperv@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arch@...r.kernel.org, anrayabh@...ux.microsoft.com,
        mikelley@...rosoft.com
Subject: Re: [PATCH v8 3/5] x86/hyperv: Add an interface to do nested
 hypercalls

On 12/8/2022 9:32 PM, Jinank Jain wrote:
>  /* Fast hypercall with 8 bytes of input and no output */
> -static inline u64 hv_do_fast_hypercall8(u16 code, u64 input1)
> +static inline u64 _hv_do_fast_hypercall8(u64 control, u16 code, u64 input1)
>  {
> -	u64 hv_status, control = (u64)code | HV_HYPERCALL_FAST_BIT;
> +	u64 hv_status;

The parameter 'code' seems to be unused in this function now.
Can we just replace it with 'control'?

>  
>  #ifdef CONFIG_X86_64
>  	{
> @@ -105,10 +111,24 @@ static inline u64 hv_do_fast_hypercall8(u16 code, u64 input1)
>  		return hv_status;
>  }
>  
> +static inline u64 hv_do_fast_hypercall8(u16 code, u64 input1)
> +{
> +	u64 control = (u64)code | HV_HYPERCALL_FAST_BIT;
> +
> +	return _hv_do_fast_hypercall8(control, code, input1);
> +}
> +
> +static inline u64 hv_do_fast_nested_hypercall8(u16 code, u64 input1)
> +{
> +	u64 control = (u64)code | HV_HYPERCALL_FAST_BIT | HV_HYPERCALL_NESTED;
> +
> +	return _hv_do_fast_hypercall8(control, code, input1);
> +}
> +
>  /* Fast hypercall with 16 bytes of input */
> -static inline u64 hv_do_fast_hypercall16(u16 code, u64 input1, u64 input2)
> +static inline u64 _hv_do_fast_hypercall16(u64 control, u16 code, u64 input1, u64 input2)
>  {
> -	u64 hv_status, control = (u64)code | HV_HYPERCALL_FAST_BIT;
> +	u64 hv_status;

Ditto

>  
>  #ifdef CONFIG_X86_64
>  	{
> @@ -139,6 +159,20 @@ static inline u64 hv_do_fast_hypercall16(u16 code, u64 input1, u64 input2)
>  	return hv_status;
>  }
>  
> +static inline u64 hv_do_fast_hypercall16(u16 code, u64 input1, u64 input2)
> +{
> +	u64 control = (u64)code | HV_HYPERCALL_FAST_BIT;
> +
> +	return _hv_do_fast_hypercall16(control, code, input1, input2);
> +}
> +
> +static inline u64 hv_do_fast_nested_hypercall16(u16 code, u64 input1, u64 input2)
> +{
> +	u64 control = (u64)code | HV_HYPERCALL_FAST_BIT | HV_HYPERCALL_NESTED;
> +
> +	return _hv_do_fast_hypercall16(control, code, input1, input2);
> +}