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From: Thomas Gleixner <tglx@linutronix.de>
To: Ingo Molnar <mingo@kernel.org>
Cc: Andi Kleen <andi@firstfloor.org>,
	x86@kernel.org, linux-kernel@vger.kernel.org,
	Andi Kleen <ak@linux.intel.com>,
	Jonathan McDowell <noodles@earth.li>
Subject: Re: [PATCH v9 2/5] x86/cpuid: Add generic table for cpuid dependencies
Date: Thu, 12 Oct 2017 17:13:34 +0200 (CEST)	[thread overview]
Message-ID: <alpine.DEB.2.20.1710121710580.1930@nanos> (raw)
In-Reply-To: <20171012080733.4y5wlghjr524cgr3@gmail.com>

On Thu, 12 Oct 2017, Ingo Molnar wrote:
> 
> * Andi Kleen <andi@firstfloor.org> wrote:
> 
> > --- /dev/null
> > +++ b/arch/x86/kernel/cpu/cpuid-deps.c
> > @@ -0,0 +1,109 @@
> > +/* Declare dependencies between CPUIDs */
> > +#include <linux/kernel.h>
> > +#include <linux/init.h>
> > +#include <linux/module.h>
> > +#include <asm/cpufeature.h>
> > +
> > +struct cpuid_dep {
> > +	unsigned short feature;
> > +	unsigned short depends;
> > +};
> 
> Why are these 16-bit fields? 16-bit data types should be avoided as much as 
> possible, as they generate suboptimal code.

I was looking at that as well and decided that we preferrably have a
compressed data structure. The code which walks the table is hardly
performance critical and the difference in text size is marginal.

Thanks,

	tglx

  parent reply	other threads:[~2017-10-12 15:13 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-10-07  0:03 Support generic disabling of all XSAVE features Andi Kleen
2017-10-07  0:03 ` [PATCH v9 1/5] x86/xsave: Move xsave initialization to after parsing early parameters Andi Kleen
2017-10-12  7:18   ` Ingo Molnar
2017-10-07  0:03 ` [PATCH v9 2/5] x86/cpuid: Add generic table for cpuid dependencies Andi Kleen
2017-10-08  8:35   ` Thomas Gleixner
2017-10-12  8:07   ` Ingo Molnar
2017-10-12  8:16     ` Ingo Molnar
2017-10-13 17:46       ` Andi Kleen
2017-10-12 15:13     ` Thomas Gleixner [this message]
2017-10-12 22:01       ` Andi Kleen
2017-10-13  5:30       ` Ingo Molnar
2017-10-13 16:36         ` Andi Kleen
2017-10-12 22:12     ` Andi Kleen
2017-10-07  0:03 ` [PATCH v9 3/5] x86/cpuid: Make clearcpuid an early param Andi Kleen
2017-10-12  8:09   ` Ingo Molnar
2017-10-07  0:03 ` [PATCH v9 4/5] x86/xsave: Make XSAVE check the base CPUID features before enabling Andi Kleen
2017-10-08  8:34   ` Thomas Gleixner
2017-10-12  8:11   ` Ingo Molnar
2017-10-13 17:48     ` Andi Kleen
2017-10-07  0:03 ` [PATCH v9 5/5] x86/xsave: Remove the explicit clearing of XSAVE dependend features Andi Kleen

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