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From: Jan Beulich <jbeulich@suse.com>
To: Jason Andryuk <jandryuk@gmail.com>
Cc: "Andrew Cooper" <andrew.cooper3@citrix.com>,
	"George Dunlap" <george.dunlap@citrix.com>,
	"Ian Jackson" <iwj@xenproject.org>,
	"Julien Grall" <julien@xen.org>,
	"Stefano Stabellini" <sstabellini@kernel.org>,
	"Wei Liu" <wl@xen.org>, "Roger Pau Monné" <roger.pau@citrix.com>,
	xen-devel <xen-devel@lists.xenproject.org>
Subject: Re: [PATCH 04/13] cpufreq: Add Hardware P-State (HWP) driver
Date: Fri, 4 Jun 2021 08:39:12 +0200	[thread overview]
Message-ID: <2d88b1db-3064-63e1-e197-9318624e6cc6@suse.com> (raw)
In-Reply-To: <CAKf6xpvCkzHOZsBY2yMQSVxq844_muaAaKd-JZUQfd7UCrXLVg@mail.gmail.com>

On 03.06.2021 13:55, Jason Andryuk wrote:
> On Fri, May 28, 2021 at 2:35 AM Jan Beulich <jbeulich@suse.com> wrote:
>> On 27.05.2021 20:50, Jason Andryuk wrote:
>>> On Wed, May 26, 2021 at 11:00 AM Jan Beulich <jbeulich@suse.com> wrote:
>>>> On 03.05.2021 21:28, Jason Andryuk wrote:
>>>>> +    hwp_verbose("HWP: FAST_IA32_HWP_REQUEST %ssupported\n",
>>>>> +                eax & CPUID6_EAX_FAST_HWP_MSR ? "" : "not ");
>>>>> +    if ( eax & CPUID6_EAX_FAST_HWP_MSR )
>>>>> +    {
>>>>> +        if ( rdmsr_safe(MSR_FAST_UNCORE_MSRS_CAPABILITY, val) )
>>>>> +            hwp_err("error rdmsr_safe(MSR_FAST_UNCORE_MSRS_CAPABILITY)\n");
>>>>> +
>>>>> +        hwp_verbose("HWP: MSR_FAST_UNCORE_MSRS_CAPABILITY: %016lx\n", val);
>>>>
>>>> Missing "else" above here?
>>>
>>> Are unbalanced braces acceptable or must they be balanced?  Is this acceptable:
>>> if ()
>>>   one;
>>> else {
>>>   two;
>>>   three;
>>> }
>>
>> Yes, it is. But I don't see how the question relates to my comment.
>> All that needs to go in the else's body is the hwp_verbose().
> 
> 'val' shouldn't be used to set features when the rdmsr fails, so the
> following code needs to be within the else.  Unless you want to rely
> on a failed rdmsr returning 0.

It is intentional for rdmsr_safe() to return a zero value when the
access faulted, so I certainly think you may rely on this.

Jan



  reply	other threads:[~2021-06-04  6:39 UTC|newest]

Thread overview: 44+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-03 19:27 [PATCH 00/13] Intel Hardware P-States (HWP) support Jason Andryuk
2021-05-03 19:27 ` [PATCH 01/13] cpufreq: Allow restricting to internal governors only Jason Andryuk
2021-05-26 13:18   ` Jan Beulich
2021-05-26 14:12     ` Jason Andryuk
2021-05-26 15:09       ` Jan Beulich
2021-05-26 16:44         ` Jason Andryuk
2021-05-03 19:27 ` [PATCH 02/13] cpufreq: Add perf_freq to cpuinfo Jason Andryuk
2021-05-26 13:24   ` Jan Beulich
2021-05-26 14:19     ` Jason Andryuk
2021-05-03 19:28 ` [PATCH 03/13] cpufreq: Export intel_feature_detect Jason Andryuk
2021-05-26 13:27   ` Jan Beulich
2021-05-26 14:44     ` Jason Andryuk
2021-05-26 15:11       ` Jan Beulich
2021-05-03 19:28 ` [PATCH 04/13] cpufreq: Add Hardware P-State (HWP) driver Jason Andryuk
2021-05-26 14:59   ` Jan Beulich
2021-05-27  7:23     ` Jan Beulich
2021-05-27 18:50     ` Jason Andryuk
2021-05-28  6:35       ` Jan Beulich
2021-06-03 11:55         ` Jason Andryuk
2021-06-04  6:39           ` Jan Beulich [this message]
2021-05-27  7:45   ` Jan Beulich
2021-05-03 19:28 ` [PATCH 05/13] xenpm: Change get-cpufreq-para output for internal Jason Andryuk
2021-05-26 15:21   ` Jan Beulich
2021-05-27  5:54     ` Jan Beulich
2021-05-03 19:28 ` [PATCH 06/13] cpufreq: Export HWP parameters to userspace Jason Andryuk
2021-05-27  7:55   ` Jan Beulich
2021-05-28 13:19     ` Jason Andryuk
2021-05-28 13:39       ` Jan Beulich
2021-05-03 19:28 ` [PATCH 07/13] libxc: Include hwp_para in definitions Jason Andryuk
2021-05-03 19:28 ` [PATCH 08/13] xenpm: Print HWP parameters Jason Andryuk
2021-05-27  8:02   ` Jan Beulich
2021-05-03 19:28 ` [PATCH 09/13] xen: Add SET_CPUFREQ_HWP xen_sysctl_pm_op Jason Andryuk
2021-05-27  8:33   ` Jan Beulich
2021-05-03 19:28 ` [PATCH 10/13] libxc: Add xc_set_cpufreq_hwp Jason Andryuk
2021-05-04  8:03   ` Jan Beulich
2021-05-04 11:31     ` Jason Andryuk
2021-05-27  9:45   ` Jan Beulich
2021-05-03 19:28 ` [PATCH 11/13] xenpm: Factor out a non-fatal cpuid_parse variant Jason Andryuk
2021-05-27  8:41   ` Jan Beulich
2021-05-03 19:28 ` [PATCH 12/13] xenpm: Add set-cpufreq-hwp subcommand Jason Andryuk
2021-05-27  9:46   ` Jan Beulich
2021-05-03 19:28 ` [PATCH 13/13] CHANGELOG: Add Intel HWP entry Jason Andryuk
2021-05-27  9:48   ` Jan Beulich
2021-05-20 14:57 ` [PATCH 00/13] Intel Hardware P-States (HWP) support Jan Beulich

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