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Date:   Fri, 13 Oct 2023 09:13:23 -0700
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Subject: Re: [PATCH] perf/x86/p4: Fix "Wunused-but-set-variable" warning
From:   Sean Christopherson <seanjc@google.com>
To:     Lucy Mielke <lucymielke@icloud.com>
Cc:     Peter Zijlstra <peterz@infradead.org>, mingo@redhat.com,
        acme@kernel.org, mark.rutland@arm.com,
        alexander.shishkin@linux.intel.com, jolsa@kernel.org,
        namhyung@kernel.org, irogers@google.com, adrian.hunter@intel.com,
        tglx@linutronix.de, bp@alien8.de, dave.hansen@linux.intel.com,
        x86@kernel.org, hpa@zytor.com, linux-perf-users@vger.kernel.org,
        linux-kernel@vger.kernel.org
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On Thu, Oct 12, 2023, Lucy Mielke wrote:
> Am Mon, Oct 09, 2023 at 09:29:50AM -0700 schrieb Sean Christopherson:
> > 
> > rdmsr() writes to "high", but nothing ever reads from high.  FWIW, I would _love_
> > for rdmsrl() to have return semantics, e.g. to be able to do:
> > 
> > 	low  = (u32)rdmsrl(MSR_IA32_MISC_ENABLE);
> > 
> > or even
> > 
> > 	if (!(rdmsrl(MSR_IA32_MISC_ENABLE) & BIT(7)))
> 
> I have taken a look and it seems to me like this macro is called quite a lot
> for different things thoughout the kernel tree, including drivers. If
> one were to change it to have return semantics instead of the way it
> currently works, you'd have to change around 300 occurences, right?

Yep, which is the only reason I haven't force the issue.