linux-kernel - Re: [patch v5 01/19] x86/cpu: Provide cpuid

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Date: Wed, 24 Jan 2024 13:25:12 +0100
From: Borislav Petkov <bp@...en8.de>
To: Thomas Gleixner <tglx@...utronix.de>
Cc: LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
	Tom Lendacky <thomas.lendacky@....com>,
	Andrew Cooper <andrew.cooper3@...rix.com>,
	Arjan van de Ven <arjan@...ux.intel.com>,
	Huang Rui <ray.huang@....com>, Juergen Gross <jgross@...e.com>,
	Dimitri Sivanich <dimitri.sivanich@....com>,
	Sohil Mehta <sohil.mehta@...el.com>,
	K Prateek Nayak <kprateek.nayak@....com>,
	Kan Liang <kan.liang@...ux.intel.com>,
	Zhang Rui <rui.zhang@...el.com>,
	"Paul E. McKenney" <paulmck@...nel.org>,
	Feng Tang <feng.tang@...el.com>,
	Andy Shevchenko <andy@...radead.org>,
	Michael Kelley <mhklinux@...look.com>,
	"Peter Zijlstra (Intel)" <peterz@...radead.org>
Subject: Re: [patch v5 01/19] x86/cpu: Provide cpuid_read() et al.

On Tue, Jan 23, 2024 at 01:53:30PM +0100, Thomas Gleixner wrote:
> +static inline void __cpuid_read(unsigned int leaf, unsigned int subleaf, u32 *regs)
> +{
> +	regs[CPUID_EAX] = leaf;
> +	regs[CPUID_ECX] = subleaf;
> +	__cpuid(regs, regs + 1, regs + 2, regs + 3);

You have defines for the regs - might as well use them:

	__cpuid(regs, regs + CPUID_EBX, regs + CPUID_ECX, regs + CPUID_EDX);

> +}
> +
> +#define cpuid_subleaf(leaf, subleaf, regs) {		\
> +	BUILD_BUG_ON(sizeof(*(regs)) != 16);		\
> +	__cpuid_read(leaf, subleaf, (u32 *)(regs));	\
> +}
> +
> +#define cpuid_leaf(leaf, regs) {			\
> +	BUILD_BUG_ON(sizeof(*(regs)) != 16);		\
> +	__cpuid_read(leaf, 0, (u32 *)(regs));		\
> +}
> +
> +static inline void __cpuid_read_reg(unsigned int leaf, unsigned int subleaf,
> +				    enum cpuid_regs_idx regidx, u32 *reg)
> +{
> +	u32 regs[4];
> +
> +	__cpuid_read(leaf, subleaf, regs);
> +	*reg = regs[regidx];

Why not do

	return regs[regidx];

instead?

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette