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From: Thomas Gleixner <tglx@linutronix.de>
To: Borislav Petkov <bp@alien8.de>
Cc: LKML <linux-kernel@vger.kernel.org>, x86@kernel.org, Tom Lendacky
 <thomas.lendacky@amd.com>, Andrew Cooper <andrew.cooper3@citrix.com>,
 Arjan van de Ven <arjan@linux.intel.com>, Huang Rui <ray.huang@amd.com>,
 Juergen Gross <jgross@suse.com>, Dimitri Sivanich
 <dimitri.sivanich@hpe.com>, Sohil Mehta <sohil.mehta@intel.com>, K Prateek
 Nayak <kprateek.nayak@amd.com>, Kan Liang <kan.liang@linux.intel.com>,
 Zhang Rui <rui.zhang@intel.com>, "Paul E. McKenney" <paulmck@kernel.org>,
 Feng Tang <feng.tang@intel.com>, Andy Shevchenko <andy@infradead.org>,
 Michael Kelley <mhklinux@outlook.com>, "Peter Zijlstra (Intel)"
 <peterz@infradead.org>
Subject: Re: [patch v5 01/19] x86/cpu: Provide cpuid_read() et al.
In-Reply-To: <20240124200207.GHZbFsv-XjMRGfp19b@fat_crate.local>
Date: Mon, 12 Feb 2024 14:57:02 +0100
Message-ID: <87le7plr9t.ffs@tglx>
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On Wed, Jan 24 2024 at 21:02, Borislav Petkov wrote:
> On Wed, Jan 24, 2024 at 01:25:12PM +0100, Borislav Petkov wrote:
>> > +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?
>
> Or do you really want to be able to use anonymous structs with bitfields
> in them and then convert them to a u32 * when passing in to
> cpuid_leaf_reg() etc in order to save yourself all the masking and
> shifting and read out the bitfields directly?
>
> I'm looking at the parse_topology() use case.
>
> Looks like it...

Yes, that's the idea.