linux-kernel - Re: [PATCH v2 1/3] selftests/resctrl: Add CPU vendor detection for Hygon

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Message-ID: <aTizyW7R8Mqj-lSJ@agluck-desk3>
Date: Tue, 9 Dec 2025 15:42:01 -0800
From: "Luck, Tony" <tony.luck@...el.com>
To: Reinette Chatre <reinette.chatre@...el.com>
CC: Xiaochen Shen <shenxiaochen@...n-hieco.net>, Fenghua Yu
	<fenghuay@...dia.com>, <bp@...en8.de>, <shuah@...nel.org>,
	<skhan@...uxfoundation.org>, <babu.moger@....com>, <james.morse@....com>,
	<Dave.Martin@....com>, <x86@...nel.org>, <linux-kernel@...r.kernel.org>,
	<linux-kselftest@...r.kernel.org>
Subject: Re: [PATCH v2 1/3] selftests/resctrl: Add CPU vendor detection for
 Hygon

On Tue, Dec 09, 2025 at 03:02:14PM -0800, Reinette Chatre wrote:

> I suggest this be simplified to not have the vendor ID be used both as a value and as a state.
> Here is some pseudo-code that should be able to accomplish this:
> 
> 
> 	unsigned int detect_vendor(void)
> 	{
> 		static bool initialized = false;
> 		static unsigned int vendor_id;
> 		...
> 		FILE *inf;
> 
> 
> 		if (initialized)
> 			return vendor_id;
> 
> 		inf = fopen("/proc/cpuinfo", "r");
> 		if (!inf) {
> 			vendor_id = 0;
> 			initialized = true;
> 			return vendor_id;
> 		}
> 
> 		/* initialize vendor_id from /proc/cpuinfo */
> 
> 		initialized = true;
> 		return vendor_id;
> 	}
> 
> 	unsigned int get_vendor(void)
> 	{
> 		unsigned int vendor;
> 		
> 		vendor = detect_vendor();
> 
> 		if (vendor == 0)
> 			ksft_print_msg(...);
> 
> 		return vendor;
> 	}

If detect_vendor() failed, this you'd get the ksft_print_msg() for every
call to get_vendor().

Why not split completly.

static unsigned int vendor_id;

void detect_vendor(void)
{
	FILE *inf = fopen("/proc/cpuinfo", "r");

	if (!inf) {
		... warning unable to get vendor id ...
	}

	... initialize from /proc/cpuinfo ...

	... warn if doesn't find a known vendor ...
}

Call detect_vendor() at the beginning of main() in each test.

Then just use "vendor_id" whenever you need to test for some vendor
specific feature.

-Tony