linux-kernel - Re: [PATCH] x86/hyperv: Fix hv_get/set

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Date:   Mon, 13 Feb 2023 14:28:29 +0000
From:   Wei Liu <wei.liu@...nel.org>
To:     Nuno Das Neves <nunodasneves@...ux.microsoft.com>
Cc:     linux-hyperv@...r.kernel.org, linux-kernel@...r.kernel.org,
        x86@...nel.org, wei.liu@...nel.org, jinankjain@...ux.microsoft.com,
        mikelley@...rosoft.com, kys@...rosoft.com,
        Tianyu.Lan@...rosoft.com, haiyangz@...rosoft.com,
        decui@...rosoft.com, tglx@...utronix.de, mingo@...hat.com,
        bp@...en8.de, dave.hansen@...ux.intel.com, hpa@...or.com
Subject: Re: [PATCH] x86/hyperv: Fix hv_get/set_register for nested bringup

A few comments on style.

On Thu, Feb 09, 2023 at 02:02:52PM -0800, Nuno Das Neves wrote:
> hv_get_nested_reg only translates SINT0, resulting in the wrong sint
> being registered by nested vmbus.

Please put a blank line between paragraphs.

> Fix the issue with new utility function hv_is_sint_reg.
> While at it, improve clarity of hv_set_non_nested_register and hv_is_synic_reg.
> 
> Signed-off-by: Nuno Das Neves <nunodasneves@...ux.microsoft.com>
> ---
>  arch/x86/include/asm/mshyperv.h | 11 +++++++----
>  arch/x86/kernel/cpu/mshyperv.c  |  8 ++++----
>  2 files changed, 11 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
> index 9ae1a344536b..684c547c1cca 100644
> --- a/arch/x86/include/asm/mshyperv.h
> +++ b/arch/x86/include/asm/mshyperv.h
> @@ -225,10 +225,13 @@ extern bool hv_isolation_type_snp(void);
>  
>  static inline bool hv_is_synic_reg(unsigned int reg)
>  {
> -	if ((reg >= HV_REGISTER_SCONTROL) &&
> -	    (reg <= HV_REGISTER_SINT15))
> -		return true;
> -	return false;
> +	return (reg >= HV_REGISTER_SCONTROL) &&
> +	       (reg <= HV_REGISTER_SINT15);
> +}

Please put a new line here.

I can fix these issues too if you don't end up sending a new version due
to other issues.

Jinank, please take a look. The code looks sensible to me, but I would
like you to have a look too.

Thanks,
Wei.

> +static inline bool hv_is_sint_reg(unsigned int reg)
> +{
> +	return (reg >= HV_REGISTER_SINT0) &&
> +	       (reg <= HV_REGISTER_SINT15);
>  }
>  
>  u64 hv_get_register(unsigned int reg);
> diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
> index 0ceb6d1f9c3c..6bd344e1200f 100644
> --- a/arch/x86/kernel/cpu/mshyperv.c
> +++ b/arch/x86/kernel/cpu/mshyperv.c
> @@ -44,6 +44,9 @@ struct ms_hyperv_info ms_hyperv;
>  #if IS_ENABLED(CONFIG_HYPERV)
>  static inline unsigned int hv_get_nested_reg(unsigned int reg)
>  {
> +	if (hv_is_sint_reg(reg))
> +		return reg - HV_REGISTER_SINT0 + HV_REGISTER_NESTED_SINT0;
> +
>  	switch (reg) {
>  	case HV_REGISTER_SIMP:
>  		return HV_REGISTER_NESTED_SIMP;
> @@ -53,8 +56,6 @@ static inline unsigned int hv_get_nested_reg(unsigned int reg)
>  		return HV_REGISTER_NESTED_SVERSION;
>  	case HV_REGISTER_SCONTROL:
>  		return HV_REGISTER_NESTED_SCONTROL;
> -	case HV_REGISTER_SINT0:
> -		return HV_REGISTER_NESTED_SINT0;
>  	case HV_REGISTER_EOM:
>  		return HV_REGISTER_NESTED_EOM;
>  	default:
> @@ -80,8 +81,7 @@ void hv_set_non_nested_register(unsigned int reg, u64 value)
>  		hv_ghcb_msr_write(reg, value);
>  
>  		/* Write proxy bit via wrmsl instruction */
> -		if (reg >= HV_REGISTER_SINT0 &&
> -		    reg <= HV_REGISTER_SINT15)
> +		if (hv_is_sint_reg(reg))
>  			wrmsrl(reg, value | 1 << 20);
>  	} else {
>  		wrmsrl(reg, value);
> -- 
> 2.25.1
>