linux-kernel - Re: [PATCH 04/14] platform/x86/intel/ifs: Remove image loading during init

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Date:   Mon, 24 Oct 2022 16:50:32 -0700
From:   Sohil Mehta <sohil.mehta@...el.com>
To:     Jithu Joseph <jithu.joseph@...el.com>
CC:     <tglx@...utronix.de>, <mingo@...hat.com>, <bp@...en8.de>,
        <dave.hansen@...ux.intel.com>, <x86@...nel.org>, <hpa@...or.com>,
        <gregkh@...uxfoundation.org>, <ashok.raj@...el.com>,
        <tony.luck@...el.com>, <linux-kernel@...r.kernel.org>,
        <platform-driver-x86@...r.kernel.org>, <patches@...ts.linux.dev>,
        <ravi.v.shankar@...el.com>, <thiago.macieira@...el.com>,
        <athenas.jimenez.gonzalez@...el.com>, <markgross@...nel.org>,
        <hdegoede@...hat.com>
Subject: Re: [PATCH 04/14] platform/x86/intel/ifs: Remove image loading during
 init

On 10/21/2022 1:34 PM, Jithu Joseph wrote:
> Existing implementation loads IFS test image during the driver
> init flow.
> 
> Dropping test image loading from the init path improves
> module load time.
> 
> Prior to starting IFS tests, the user has to load one of
> the IFS test images by writing to the current_batch sysfs file.
> 

The kernel is still unaware of the 'current_batch' sysfs file. It will 
be introduced in patch 12. You can avoid the reference here.

> Removing IFS test image  loading during init also allows us to
> make ifs_sem static as it is used only within sysfs.c.
> 

Does something like this sound better?

IFS test image is unnecessarily loaded during driver initialization. The 
user has to load one when starting the tests.

Drop image loading during ifs_init() and improve module load time. As a 
consequence, make ifs_sem static as it is only used within sysfs.c

> diff --git a/drivers/platform/x86/intel/ifs/core.c b/drivers/platform/x86/intel/ifs/core.c
> index 27204e3d674d..5fb7f655c291 100644
> --- a/drivers/platform/x86/intel/ifs/core.c
> +++ b/drivers/platform/x86/intel/ifs/core.c
> @@ -51,12 +51,8 @@ static int __init ifs_init(void)
>   	ifs_device.misc.groups = ifs_get_groups();
>   
>   	if ((msrval & BIT(ifs_device.data.integrity_cap_bit)) &&

Is there a reason to store the integrity cap constant in the device.data 
global structure?

.data = {
	.integrity_cap_bit = MSR_INTEGRITY_CAPS_PERIODIC_BIST_BIT,
},

IIUC, you are basically reading an MSR and testing a bit within? You 
already have an BIT macro (unused) for that.

#define MSR_INTEGRITY_CAPS_PERIODIC_BIST 
BIT(MSR_INTEGRITY_CAPS_PERIODIC_BIST_BIT)



> -	    !misc_register(&ifs_device.misc)) {
> -		down(&ifs_sem);
> -		ifs_load_firmware(ifs_device.misc.this_device);
> -		up(&ifs_sem);
> +	    !misc_register(&ifs_device.misc))
>   		return 0;
> -	}
>   
>   	return -ENODEV;
>   }

Sohil