linux-kernel - Re: [PATCH 09/14] platform/x86/intel/ifs: Use generic microcode headers and functions

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Date:   Tue, 1 Nov 2022 11:37:31 -0700
From:   Sohil Mehta <sohil.mehta@...el.com>
To:     Jithu Joseph <jithu.joseph@...el.com>, <hdegoede@...hat.com>,
        <markgross@...nel.org>
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>
Subject: Re: [PATCH 09/14] platform/x86/intel/ifs: Use generic microcode
 headers and functions

On 10/21/2022 1:34 PM, Jithu Joseph wrote:
> Newer IFS test image headers will use  microcode_header_intel->hdrver = 2,
> so as to distinguish it from microcode images and older IFS test images.
> 

IIUC, older IFS test images would no longer be supported. Have they been 
released publicly?

What would happen if someone tries to load one? I am guessing one of the 
error checks would catch it. It might be useful to describe this error 
signature in the commit message.

>   
> -	if ((data_size + MC_HEADER_SIZE > total_size) || (total_size % sizeof(u32))) {
> -		dev_err(dev, "bad ifs data file size.\n");
> +	if (data->hdrver != IFS_HEADER_VER) {
> +		dev_err(dev, "Header version %d not supported\n", data->hdrver);
>   		return -EINVAL;
>   	}
>   
> -	if (mc_header->ldrver != 1 || mc_header->hdrver != 1) {
> -		dev_err(dev, "invalid/unknown ifs update format.\n");
> +	if (microcode_intel_sanity_check((void *)data, true, IFS_HEADER_VER)) {

I referred to this in a another patch. The data->hdrver is already 
verified above, why is there a need to pass it as a parameter as well.

> +		dev_err(dev, "sanity check failed\n");
>   		return -EINVAL;
>   	}
>   
> -	mc = (u32 *)mc_header;
> -	sum = 0;
> -	for (int i = 0; i < total_size / sizeof(u32); i++)
> -		sum += mc[i];
> +	intel_cpu_collect_info(&uci);
>   
> -	if (sum) {
> -		dev_err(dev, "bad ifs data checksum, aborting.\n");
> +	if (!microcode_intel_find_matching_signature((void *)data,
> +						     uci.cpu_sig.sig,
> +						     uci.cpu_sig.pf)) {
> +		dev_err(dev, "cpu signature, pf not matching\n");

What does pf stand for? It would be good to avoid abbreviations for 
error logging.


>   /*
>    * Load ifs image. Before loading ifs module, the ifs image must be located
>    * in /lib/firmware/intel/ifs and named as {family/model/stepping}.{testname}.
> @@ -252,12 +189,11 @@ int ifs_load_firmware(struct device *dev)
>   		goto done;
>   	}
>   
> -	if (!ifs_image_sanity_check(dev, (struct microcode_header_intel *)fw->data)) {
> -		dev_err(dev, "ifs header sanity check failed\n");
> +	ret = ifs_image_sanity_check(dev, (struct microcode_header_intel *)fw->data);
> +	if (ret)
>   		goto release;
> -	}
>   
> -	ifs_header_ptr = (struct ifs_header *)fw->data;
> +	ifs_header_ptr = (struct microcode_header_intel *)fw->data;

The use of a global ifs_header_ptr seems problematic. The semaphore 
operation before calling ifs_load_firmware() makes it seem concurrency 
is expected. Can ifs_load_firmware() really be called concurrently?

If that is not true can we use a mutex for synchronization?

Sohil