linux-kernel - Re: [PATCH] perf/x86/intel/uncore: Add error handling for uncore_msr_box

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Message-ID: <Z-wvRLi55EnMGniG@gmail.com>
Date: Tue, 1 Apr 2025 20:24:04 +0200
From: Ingo Molnar <mingo@...nel.org>
To: Wentao Liang <vulab@...as.ac.cn>
Cc: peterz@...radead.org, mingo@...hat.com, acme@...nel.org,
	namhyung@...nel.org, mark.rutland@....com,
	alexander.shishkin@...ux.intel.com, jolsa@...nel.org,
	irogers@...gle.com, adrian.hunter@...el.com,
	kan.liang@...ux.intel.com, tglx@...utronix.de, bp@...en8.de,
	dave.hansen@...ux.intel.com, x86@...nel.org, hpa@...or.com,
	linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Subject: Re: [PATCH] perf/x86/intel/uncore: Add error handling for
 uncore_msr_box_ctl()


* Wentao Liang <vulab@...as.ac.cn> wrote:

> In mtl_uncore_msr_init_box(), the return value of uncore_msr_box_ctl()
> needs to be checked before being used as the parameter of wrmsrl().
> A proper implementation can be found in ivbep_uncore_msr_init_box().
> 
> Add error handling for uncore_msr_box_ctl() to ensure the MSR write
> operation is only performed when a valid MSR address is returned.
> 
> Fixes: c828441f21dd ("perf/x86/intel/uncore: Add Meteor Lake support")
> Cc: stable@...r.kernel.org # v6.3+
> Signed-off-by: Wentao Liang <vulab@...as.ac.cn>
> ---
>  arch/x86/events/intel/uncore_snb.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/events/intel/uncore_snb.c b/arch/x86/events/intel/uncore_snb.c
> index 3934e1e4e3b1..84070388f495 100644
> --- a/arch/x86/events/intel/uncore_snb.c
> +++ b/arch/x86/events/intel/uncore_snb.c
> @@ -691,7 +691,10 @@ static struct intel_uncore_type mtl_uncore_hac_cbox = {
>  
>  static void mtl_uncore_msr_init_box(struct intel_uncore_box *box)
>  {
> -	wrmsrl(uncore_msr_box_ctl(box), SNB_UNC_GLOBAL_CTL_EN);
> +	unsigned int msr = uncore_msr_box_ctl(box);
> +
> +	if (msr)
> +		wrmsrl(msr, SNB_UNC_GLOBAL_CTL_EN);

Exactly what happens without this patch, do we crash during boot due to 
the incorrect wrmsr()?

Thanks,

	Ingo