Re: [PATCH 12/14] platform/x86/intel/ifs: Add current_batch sysfs entry

From: Sohil Mehta <sohil.mehta@intel.com>
To: Jithu Joseph <jithu.joseph@intel.com>, <hdegoede@redhat.com>,
	<markgross@kernel.org>
Cc: <tglx@linutronix.de>, <mingo@redhat.com>, <bp@alien8.de>,
	<dave.hansen@linux.intel.com>, <x86@kernel.org>, <hpa@zytor.com>,
	<gregkh@linuxfoundation.org>, <ashok.raj@intel.com>,
	<tony.luck@intel.com>, <linux-kernel@vger.kernel.org>,
	<platform-driver-x86@vger.kernel.org>, <patches@lists.linux.dev>,
	<ravi.v.shankar@intel.com>, <thiago.macieira@intel.com>,
	<athenas.jimenez.gonzalez@intel.com>
Subject: Re: [PATCH 12/14] platform/x86/intel/ifs: Add current_batch sysfs entry
Date: Tue, 1 Nov 2022 15:26:01 -0700	[thread overview]
Message-ID: <9bfd45cb-ab5c-1d46-1e16-03417c89298b@intel.com> (raw)
In-Reply-To: <20221021203413.1220137-13-jithu.joseph@intel.com>

On 10/21/2022 1:34 PM, Jithu Joseph wrote:
> Initial implementation assumed a single IFS test image file with a
> fixed name ff-mm-ss.scan. (where ff, mm, ss refers to family, model
> and stepping  of the core)
> 
> Subsequently, it became evident that supporting more than one
> test image file is needed to provide more comprehensive
> test coverage. (Test coverage in this scenario refers to testing
> more transistors in the core to identify faults)
> 
> The other alternative of increasing the size of a single scan test image
> file would not work as the  upper bound is limited by the size of memory
> area reserved by BIOS for loading IFS test image.
> 
> Introduce "current_batch" file which accepts a number. Writing a
> number to the current_batch file would load the test image file by name
> ff-mm-ss-<xy>.scan, where <xy> is the number written to the
> "current_batch" file in hex. 

Any specific reasoning why the name "current_batch" was chosen? To me, 
batch seems to suggest multiple or a group of files. But in reality only 
one test file is loaded at a time.

Naming can sometimes be quite subjective so it might be useful to get 
multiple opinions here.

As per my understanding, there is sysfs file called run_test which runs 
a loaded test. Instead of current_batch how about the name load_test (or 
maybe current_test)?

load_test - Write a number less than or equal to 0xff to load an IFS 
test image. (Description as-is from the documentation patch)

>    * Running tests
>    * -------------
> @@ -207,6 +217,7 @@ struct ifs_data {
>   	int	status;
>   	u64	scan_details;
>   	int	cur_batch;
> +	int	test_num;
>   };
>   
>   struct ifs_work {
> diff --git a/drivers/platform/x86/intel/ifs/core.c b/drivers/platform/x86/intel/ifs/core.c
> index 5fb7f655c291..1f040837e8eb 100644
> --- a/drivers/platform/x86/intel/ifs/core.c
> +++ b/drivers/platform/x86/intel/ifs/core.c
> @@ -22,6 +22,7 @@ MODULE_DEVICE_TABLE(x86cpu, ifs_cpu_ids);
>   static struct ifs_device ifs_device = {
>   	.data = {
>   		.integrity_cap_bit = MSR_INTEGRITY_CAPS_PERIODIC_BIST_BIT,
> +		.test_num = 0,

Is this initialization really needed? Wouldn't it default to 0?

Maybe if you explain what does test_num refer to it might answer the above?

> +static ssize_t current_batch_show(struct device *dev,
> +				  struct device_attribute *attr, char *buf)
> +{
> +	struct ifs_data *ifsd = ifs_get_data(dev);
> +
> +	if (!ifsd->loaded)
> +		return sysfs_emit(buf, "%s\n", "none");

Why not:

sysfs_emit(buf, "none\n");

> +	else
> +		return sysfs_emit(buf, "0x%02x\n", ifsd->cur_batch);
> +}

Sohil