linux-kernel - Re: [PATCH v2 12/14] platform/x86/intel/ifs: Add current

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Message-ID: <1745359.VLH7GnMWUR@tjmaciei-mobl5>
Date:   Sun, 13 Nov 2022 13:40:56 -0800
From:   Thiago Macieira <thiago.macieira@...el.com>
To:     Ashok Raj <ashok.raj@...el.com>, Borislav Petkov <bp@...en8.de>
Cc:     "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "Luck, Tony" <tony.luck@...el.com>,
        "Joseph, Jithu" <jithu.joseph@...el.com>,
        "hdegoede@...hat.com" <hdegoede@...hat.com>,
        "markgross@...nel.org" <markgross@...nel.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
        "x86@...nel.org" <x86@...nel.org>, "hpa@...or.com" <hpa@...or.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "platform-driver-x86@...r.kernel.org" 
        <platform-driver-x86@...r.kernel.org>,
        "patches@...ts.linux.dev" <patches@...ts.linux.dev>,
        "Shankar, Ravi V" <ravi.v.shankar@...el.com>,
        "Jimenez Gonzalez, Athenas" <athenas.jimenez.gonzalez@...el.com>,
        "Mehta, Sohil" <sohil.mehta@...el.com>
Subject: Re: [PATCH v2 12/14] platform/x86/intel/ifs: Add current_batch sysfs entry

On Sunday, 13 November 2022 07:58:52 PST Borislav Petkov wrote:
> * simply try *all* files in a directory

By the way, we don't want that.

It's possible that different steppings of the same generation will have the 
same test scan files, with the extended signature informing that they are valid 
for this stepping too (see find_matching_signature())), because these files are 
going to be pretty big, in the order of a hundred MB each. That means we will 
either see symlinked or hardlinked files in the directory.

If you blindly try them all, you're going to spend twice or three times as 
long as necessary to complete the scan. With the timeout in question for at 
least Sapphire Rapids, we're talking about a difference measured in hours.
-- 
Thiago Macieira - thiago.macieira (AT) intel.com
  Cloud Software Architect - Intel DCAI Cloud Engineering