linux-kernel - Re: [PATCH v1 3/3] x86/msr: Convert a native_wrmsr() use to native

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Message-ID: <aCYH0UQzO_Ek27js@gmail.com>
Date: Thu, 15 May 2025 17:27:13 +0200
From: Ingo Molnar <mingo@...nel.org>
To: "Xin Li (Intel)" <xin@...or.com>
Cc: linux-kernel@...r.kernel.org, xen-devel@...ts.xenproject.org,
	linux-acpi@...r.kernel.org, tglx@...utronix.de, bp@...en8.de,
	dave.hansen@...ux.intel.com, x86@...nel.org, hpa@...or.com,
	peterz@...radead.org, jgross@...e.com, boris.ostrovsky@...cle.com,
	rafael@...nel.org, lenb@...nel.org
Subject: Re: [PATCH v1 3/3] x86/msr: Convert a native_wrmsr() use to
 native_wrmsrq()


* Xin Li (Intel) <xin@...or.com> wrote:

> Convert a native_wrmsr() use to native_wrmsrq() to zap meaningless type
> conversions when a u64 MSR value is splitted into two u32.
> 
> Signed-off-by: Xin Li (Intel) <xin@...or.com>
> ---
>  arch/x86/coco/sev/core.c | 7 +------
>  1 file changed, 1 insertion(+), 6 deletions(-)
> 
> diff --git a/arch/x86/coco/sev/core.c b/arch/x86/coco/sev/core.c
> index ff82151f7718..b3ce6fc8b62d 100644
> --- a/arch/x86/coco/sev/core.c
> +++ b/arch/x86/coco/sev/core.c
> @@ -282,12 +282,7 @@ static inline u64 sev_es_rd_ghcb_msr(void)
>  
>  static __always_inline void sev_es_wr_ghcb_msr(u64 val)
>  {
> -	u32 low, high;
> -
> -	low  = (u32)(val);
> -	high = (u32)(val >> 32);
> -
> -	native_wrmsr(MSR_AMD64_SEV_ES_GHCB, low, high);
> +	native_wrmsrq(MSR_AMD64_SEV_ES_GHCB, val);

BTW., at this point we should probably just replace 
sev_es_wr_ghcb_msr() calls with direct calls to:

	native_wrmsrq(MSR_AMD64_SEV_ES_GHCB, ...);

as sev_es_wr_ghcb_msr() is now basically an open-coded native_wrmsrq().

Thanks,

	Ingo