[LTP] [PATCH v6] high_freq_hwp_cap_cppc.c: new test

[Kubaj, Piotr]

2026-03-25 (水) の 12:24 +0000 に Andrea Cervesato さんは書きました:
> Hi Piotr,
> 
> Thanks for the new test. A few issues below.
> 
> > +/*
> > + * Copyright (C) 2026 Intel - http://www.intel.com/
> > + */
> 
> The copyright line should include an author name and email, e.g.:
> 
>   Copyright (c) 2026 Piotr Kubaj <piotr.kubaj@intel.com>
> 
> > +		if (i)
> > +			SAFE_FILE_SCANF(path, "%d", &online);
> 
> SAFE_FILE_SCANF with "%d" expects a pointer to int, but `online` is
> bool (typically 1 byte). This is undefined behavior and will likely
> corrupt the stack on little-endian. Please use `int online = 1;`
> instead.
> 
> This should be spotted by any static analyzer or clangd..and even
> gcc shows this error.
For the record: 
GCC does NOT print a warning while compiling that code. At least with
the default set of options when building on Debian 13 with stock GCC
14.2.0.

> 
> > +		snprintf(path, sizeof(path), "/dev/cpu/%d/msr",
> > i);
> > +		int fd = SAFE_OPEN(path, O_RDONLY);
> > +
> > +		SAFE_PREAD(1, fd, &msr_highest_perf,
> > sizeof(msr_highest_perf), 0x771);
> 
> SAFE_CLOSE(fd) right after it has been used. There's no need to keep
> it
> open after pread().
> 
> > +		msr_highest_perf &= (1ULL << 8) - 1;
> 
> 0x771 and the 8-bit mask are magic numbers. Named defines would
> help readability, e.g.:
> 
>   #define MSR_HWP_CAPABILITIES  0x771
>   #define HIGHEST_PERF_MASK     0xFF
> 
> The test fails because msr device is not available, so you need:
> 
>   .needs_drivers = (const char *const [])
> {                                                                    
>                                     
>      
> "msr",                                                               
>                                                                      
>    
>      
> NULL                                                                 
>                                                                      
>    
>   },
> 
> And probably the CONFIG_X86_MSR=y check as well.
> 
> Regards,
> --
> Andrea Cervesato
> SUSE QE Automation Engineer Linux
> andrea.cervesato@suse.com
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