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Date: Mon, 29 Jun 2026 13:33:46 +0200
From: Ingo Molnar <mingo@kernel.org>
To: Juergen Gross <jgross@suse.com>
Cc: linux-kernel@vger.kernel.org, x86@kernel.org,
	Thomas Gleixner <tglx@kernel.org>, Ingo Molnar <mingo@redhat.com>,
	Borislav Petkov <bp@alien8.de>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	"H. Peter Anvin" <hpa@zytor.com>
Subject: Re: [PATCH 05/32] x86/mtrr: Stop using 32-bit MSR interfaces
Message-ID: <akJYGo0u9ANWMi3g@gmail.com>
References: <20260629060526.3638272-1-jgross@suse.com>
 <20260629060526.3638272-6-jgross@suse.com>
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In-Reply-To: <20260629060526.3638272-6-jgross@suse.com>


* Juergen Gross <jgross@suse.com> wrote:

>  amd_get_mtrr(unsigned int reg, unsigned long *base,
>  	     unsigned long *size, mtrr_type *type)
>  {
> -	unsigned long low, high;
> +	unsigned long val;
> +	struct msr msr;

So, 'struct msr' is defined in <asm/msr.h>, but:

>  static void
>  amd_set_mtrr(unsigned int reg, unsigned long base, unsigned long size, mtrr_type type)
>  {
> -	u32 regs[2];
> +	union {
> +		u32 regs[2];
> +		u64 val;
> +	} msr;

Why do we use a local anonymous union here with overlapping
nomenclature and a confusingly different but (AFAICS) functionally
equivalent definition to 'struct msr'?

Thanks,

	Ingo