linux-kernel - Re: [PATCH v2 02/12] x86/sev: Replace call of native_wrmsr() with native

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Message-ID: <85v7krqm5v.fsf@amd.com>
Date: Tue, 7 Oct 2025 06:08:12 +0000
From: Nikunj A Dadhania <nikunj@....com>
To: Juergen Gross <jgross@...e.com>, <linux-kernel@...r.kernel.org>,
	<x86@...nel.org>, <thomas.lendacky@....com>
CC: <xin@...or.com>, Juergen Gross <jgross@...e.com>, Thomas Gleixner
	<tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov
	<bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>, "H. Peter Anvin"
	<hpa@...or.com>
Subject: Re: [PATCH v2 02/12] x86/sev: Replace call of native_wrmsr() with
 native_wrmsrq()

Juergen Gross <jgross@...e.com> writes:

> In sev_es_wr_ghcb_msr() the 64 bit MSR value is split into 2 32 bit
> values in order to call native_wrmsr(), which will combine the values
> into a 64 bit value again.
>
> Just use native_wrmsrq() instead.
>
> Signed-off-by: Juergen Gross <jgross@...e.com>

Reviewed-by: Nikunj A Dadhania <nikunj@....com>

> ---
> V2:
> - new patch
> ---
>  arch/x86/include/asm/sev-internal.h | 7 +------
>  1 file changed, 1 insertion(+), 6 deletions(-)
>
> diff --git a/arch/x86/include/asm/sev-internal.h b/arch/x86/include/asm/sev-internal.h
> index 3dfd306d1c9e..f5d6fb3b5916 100644
> --- a/arch/x86/include/asm/sev-internal.h
> +++ b/arch/x86/include/asm/sev-internal.h
> @@ -89,12 +89,7 @@ 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);
>  }
>  
>  void snp_register_ghcb_early(unsigned long paddr);
> -- 
> 2.51.0