Re: [PATCH] x86/resctrl: Fix unused variable warning in cache_alloc_hsw_probe()

[Bagas Sanjaya <bagasdotme@gmail.com>]

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On Tue, Oct 31, 2023 at 03:05:34PM -0700, Tony Luck wrote:
> In a "W=1" build gcc throws a warning:
> 
> arch/x86/kernel/cpu/resctrl/core.c: In function ‘cache_alloc_hsw_probe’:
> arch/x86/kernel/cpu/resctrl/core.c:139:16: warning: variable ‘h’ set but not used
> 
> Fix by switching from rdmsr() to rdmsrl() using a single u64 argument
> for the MSR value instead of the pair of u32 for the high and low
> halves.
> 
> Signed-off-by: Tony Luck <tony.luck@intel.com>
> ---
> This has been annoying me for a while as the only warning from the
> resctrl code when building with W=1.
> 
> N.B. compile tested only. I don't have a Haswell system to check this works.
> 
>  arch/x86/kernel/cpu/resctrl/core.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/resctrl/core.c b/arch/x86/kernel/cpu/resctrl/core.c
> index 19e0681f0435..4084131d391d 100644
> --- a/arch/x86/kernel/cpu/resctrl/core.c
> +++ b/arch/x86/kernel/cpu/resctrl/core.c
> @@ -136,15 +136,16 @@ static inline void cache_alloc_hsw_probe(void)
>  {
>  	struct rdt_hw_resource *hw_res = &rdt_resources_all[RDT_RESOURCE_L3];
>  	struct rdt_resource *r  = &hw_res->r_resctrl;
> -	u32 l, h, max_cbm = BIT_MASK(20) - 1;
> +	u32 max_cbm = BIT_MASK(20) - 1;
> +	u64 l3_cbm_0;
>  
>  	if (wrmsr_safe(MSR_IA32_L3_CBM_BASE, max_cbm, 0))
>  		return;
>  
> -	rdmsr(MSR_IA32_L3_CBM_BASE, l, h);
> +	rdmsrl(MSR_IA32_L3_CBM_BASE, l3_cbm_0);
>  
>  	/* If all the bits were set in MSR, return success */
> -	if (l != max_cbm)
> +	if (l3_cbm_0 != max_cbm)
>  		return;
>  
>  	hw_res->num_closid = 4;

No noticeable regressions on my Acer Aspire E15 (the laptop uses Intel Core
i3 Haswell), thanks!

Tested-by: Bagas Sanjaya <bagasdotme@gmail.com>

-- 
An old man doll... just what I always wanted! - Clara

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