linux-kernel - Re: [PATCH 2/2] cpupower: fix amd cpu (family >= 0x17) active state issue

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Date:   Mon, 29 Mar 2021 12:11:44 +0800
From:   xufuhai <xufuhai1992@...il.com>
To:     Shuah Khan <skhan@...uxfoundation.org>, linux@...inikbrodowski.net,
        sherry.hurwitz@....com, trenn@...e.com, linux-pm@...r.kernel.org,
        rrichter@....com, nathan.fontenot@....com, bp@...e.de,
        latha@...ux.vnet.ibm.com, linux-kernel@...r.kernel.org
Cc:     lishujin@...ishou.com
Subject: Re: [PATCH 2/2] cpupower: fix amd cpu (family >= 0x17) active state
 issue

yeah Shuah~ thanks for your reply

For this issue, not meaning "current CPU frequency" but "boost state support--->Active" during 
"cpupower frequency-info" command as below:

	boost state support:
    		Supported: yes
    		Active: yes/no

I think the state returned from the command for amd cpu (family >= 0x17) should be like as below:

	as non-root Active state:
		Active: Error while evaluating Boost Capabilities on CPU xx -- are you root?
	
	as root Active state:
		Active: yes (if supported)
			no  (if not supprted)

I don't wanna see the state returned like below:
	
	as non-root Active state:
		Active: no
	
	as root Active state:
		Active: yes (if supported)
			no  (if not supprted)
	
I will paste the related code by detailed for showing the issue:
	
	if amd cpu family >= 0x17 , will run read_msr function via read /dev/cpu/%d/msr. For non-root
caller can not open msr node due to having no permission, but cpufreq_has_boost_support will return 0 to 
upper caller function that not means caller no permission to read /dev/cpu/%d/msr. I believe we should
return negative value for the condition:

-----------------------------------------------------
/linux/tools/power/cpupower/utils/helper/misc.c
cpufreq_has_boost_support:
 
	if (cpupower_cpu_info.caps & CPUPOWER_CAP_AMD_CPB) {
		*support = 1;

		/* AMD Family 0x17 does not utilize PCI D18F4 like prior
		 * families and has no fixed discrete boost states but
		 * has Hardware determined variable increments instead.
		 */

		if (cpupower_cpu_info.caps & CPUPOWER_CAP_AMD_CPB_MSR) {
			if (!read_msr(cpu, MSR_AMD_HWCR, &val)) {
				if (!(val & CPUPOWER_AMD_CPBDIS))
					*active = 1;
			}
		} else {
			ret = amd_pci_get_num_boost_states(active, states);
			if (ret)
				return ret;
		}
	} else if (cpupower_cpu_info.caps & CPUPOWER_CAP_INTEL_IDA)
		*support = *active = 1;
	return 0;
---------------------------------------------------



在 2021/3/27 上午4:13, Shuah Khan 写道:
> On 3/24/21 4:28 AM, xufuhai wrote:
>> From: xufuhai <xufuhai@...ishou.com>
>>
>> If the read_msr function is executed by a non-root user, the function
>> returns -1, which means that there is no permission to access /dev/cpu/%d/msr,
>> but cpufreq_has_boost_support should also return -1 immediately, and should not
>> follow the original logic to return 0, which will cause amd The cpupower tool
>> returns the turbo active status as 0.
>>
>> Reproduce procedure:
>>          cpupower frequency-info
>>
> 
> Please run get_maintainer.pl and send patch maintainers
> and others suggested by the tool. I don't see this in my
> Inbox for me to review/accept and send it to pm maintainer.
> 
> Please include before and after the patch when you run
> cpupower frequency-info
> 
> thanks,
> -- Shuah
>