linux-kernel - Re: [PATCH v4 08/18] x86/intel_rdt: Pick up L3/L2 RDT parameters from CPUID

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Date:   Mon, 17 Oct 2016 14:22:08 -0700
From:   Fenghua Yu <fenghua.yu@...el.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Fenghua Yu <fenghua.yu@...el.com>,
        "H. Peter Anvin" <h.peter.anvin@...el.com>,
        Ingo Molnar <mingo@...e.hu>, Tony Luck <tony.luck@...el.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Stephane Eranian <eranian@...gle.com>,
        Borislav Petkov <bp@...e.de>,
        Dave Hansen <dave.hansen@...el.com>,
        Nilay Vaish <nilayvaish@...il.com>, Shaohua Li <shli@...com>,
        David Carrillo-Cisneros <davidcc@...gle.com>,
        Ravi V Shankar <ravi.v.shankar@...el.com>,
        Sai Prakhya <sai.praneeth.prakhya@...el.com>,
        Vikas Shivappa <vikas.shivappa@...ux.intel.com>,
        linux-kernel <linux-kernel@...r.kernel.org>, x86 <x86@...nel.org>
Subject: Re: [PATCH v4 08/18] x86/intel_rdt: Pick up L3/L2 RDT parameters
 from CPUID

On Mon, Oct 17, 2016 at 07:02:19PM +0200, Thomas Gleixner wrote:
> On Mon, 17 Oct 2016, Fenghua Yu wrote:
> > On Mon, Oct 17, 2016 at 03:45:32PM +0200, Thomas Gleixner wrote:
> > > I wonder whether this is the proper abstraction level. We might as well do
> > > the following:
> > > 
> > > rdtresources[] = {
> > >      {
> > > 	.name	= "L3",
> > >      },
> > >      {
> > > 	.name	= "L3Data",
> > >      },
> > >      {
> > > 	.name	= "L3Code",
> > >      },
> > > 
> > > and enable either L3 or L3Data+L3Code. Not sure if that makes things
> > > simpler, but it's definitely worth a thought or two.
> > 
> > This way will be better than having cdp_enabled/capable for L3 and not
> > for L2.
> 
> So you need to change the struct to have capable and enabled
> 
> > > static void rdt_get_config(int idx, struct rdt_resource *r)
> > > {
> > > 	union cpuid_0x10_1_eax eax;
> > > 	union cpuid_0x10_1_edx edx;
> > > 	u32 ebx, ecx;
> > > 
> > > 	cpuid_count(0x00000010, idx, &eax.full, &ebx, &ecx, &edx.full);
> > > 	r->max_closid = edx.split.cos_max + 1;
> > > 	r->num_closid = r->max_closid;
> > > 	r->cbm_len = eax.split.cbm_len + 1;
> > > 	r->max_cbm = BIT_MASK(eax.split.cbm_len + 1) - 1;
> > > 	r->enabled = true;
> 
> And set 
> 
>     	r->capable = true; 
> 
> here instead of r->enabled and set r->enabled at mount time for the
> resources depending on the mount flags.

Neat code change!
 
Thanks,

-Fenghua