From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E77E81374 for ; Tue, 19 Apr 2022 16:48:39 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 19F5EC385A7; Tue, 19 Apr 2022 16:48:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1650386919; bh=QOMS7KLEHZGEz3no8RbaBIVj+K/SNB015Dr7S2LBI7g=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=YWnqwfS6FQOqhotaDyxXSpeMaZVt6GxtLZhWlcqTx0VaXaxxzthVaONrVNl4Fpg+M U3iIBFkMBV0Da0G/8cK0LS3rdfqQC2URdVDjnTOay6z7vMmcTCU9+0RwiHlfknojAh /2vClM2WnTy6W4VU+0MgMbdVvrjS2swwKMBwTXSQ= Date: Tue, 19 Apr 2022 18:48:37 +0200 From: Greg KH To: Tony Luck Cc: hdegoede@redhat.com, markgross@kernel.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, corbet@lwn.net, andriy.shevchenko@linux.intel.com, jithu.joseph@intel.com, ashok.raj@intel.com, rostedt@goodmis.org, dan.j.williams@intel.com, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, platform-driver-x86@vger.kernel.org, patches@lists.linux.dev, ravi.v.shankar@intel.com Subject: Re: [PATCH v3 02/11] Documentation: In-Field Scan Message-ID: References: <20220407191347.9681-1-jithu.joseph@intel.com> <20220419163859.2228874-1-tony.luck@intel.com> <20220419163859.2228874-3-tony.luck@intel.com> Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220419163859.2228874-3-tony.luck@intel.com> On Tue, Apr 19, 2022 at 09:38:50AM -0700, Tony Luck wrote: > Add documentation for In-Field Scan (IFS). This documentation > describes the basics of IFS, the loading IFS image, chunk > authentication, running scan and how to check result via sysfs > as well as tunable parameters. > > The CORE_CAPABILITIES MSR enumerates whether IFS is supported. > > The full github location for distributing the IFS images is > still being decided. So just a placeholder included for now > in the documentation. > > Future CPUs will support more than one type of test. Plan for > that now by using a ".0" suffix on the ABI directory names. > Additional test types will use ".1", etc. > > Reviewed-by: Dan Williams > Signed-off-by: Tony Luck > --- > Documentation/x86/ifs.rst | 101 ++++++++++++++++++++++++++++++++++++ > Documentation/x86/index.rst | 1 + > 2 files changed, 102 insertions(+) > create mode 100644 Documentation/x86/ifs.rst > > diff --git a/Documentation/x86/ifs.rst b/Documentation/x86/ifs.rst > new file mode 100644 > index 000000000000..62f3c07d433a > --- /dev/null > +++ b/Documentation/x86/ifs.rst > @@ -0,0 +1,101 @@ > +.. SPDX-License-Identifier: GPL-2.0 > + > +============= > +In-Field Scan > +============= > + > +Introduction > +------------ > + > +In Field Scan (IFS) is a hardware feature to run circuit level tests on > +a CPU core to detect problems that are not caught by parity or ECC checks. > +Future CPUs will support more than one type of test which will show up > +with a new platform-device instance-id, for now only .0 is exposed. > + > + > +IFS Image > +--------- > + > +Intel provides a firmware file containing the scan tests via > +github [#f1]_. Similar to microcode there is a separate file for each > +family-model-stepping. > + > +IFS Image Loading > +----------------- > + > +The driver loads the tests into memory reserved BIOS local to each CPU > +socket in a two step process using writes to MSRs to first load the > +SHA hashes for the test. Then the tests themselves. Status MSRs provide > +feedback on the success/failure of these steps. When a new test file > +is installed it can be loaded by writing to the driver reload file:: > + > + # echo 1 > /sys/bus/platform/drivers/intel_ifs.0/reload > + > +Similar to microcode, the current version of the scan tests is stored > +in a fixed location: /lib/firmware/intel/ifs.0/family-model-stepping.scan > + > +Running tests > +------------- > + > +Tests are run by the driver synchronizing execution of all threads on a > +core and then writing to the ACTIVATE_SCAN MSR on all threads. Instruction > +execution continues when: > + > +1) All tests have completed. > +2) Execution was interrupted. > +3) A test detected a problem. > + > +In all cases reading the SCAN_STATUS MSR provides details on what > +happened. The driver makes the value of this MSR visible to applications > +via the "details" file (see below). Interrupted tests may be restarted. > + > +The IFS driver provides sysfs interfaces via /sys/devices/platform/intel_ifs.0/ > +to control execution: > + > +Test a specific core:: > + > + # echo > /sys/devices/platform/intel_ifs.0/run_test > + > +when HT is enabled any of the sibling cpu# can be specified to test its > +corresponding physical core. Since the tests are per physical core, the > +result of testing any thread is same. It is only necessary to test one > +thread. > + > +For e.g. to test core corresponding to cpu5 > + > + # echo 5 > /sys/devices/platform/intel_ifs.0/run_test > + > +Results of the last test is provided in /sys:: > + > + $ cat /sys/devices/platform/intel_ifs.0/status > + pass sysfs documentation belongs in Documentation/ABI/ And why not just include this whole thing in the driver itself and suck the documentation out of that? No need to have a separate file. thanks, greg k-h