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Date: Fri, 15 Aug 2025 15:04:36 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Sean Christopherson <seanjc@google.com>
Cc: Marc Zyngier <maz@kernel.org>, Oliver Upton <oliver.upton@linux.dev>,
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Subject: Re: [PATCH v5 09/44] perf/x86: Switch LVTPC to/from mediated PMI
 vector on guest load/put context
Message-ID: <20250815130436.GA3289052@noisy.programming.kicks-ass.net>
References: <20250806195706.1650976-1-seanjc@google.com>
 <20250806195706.1650976-10-seanjc@google.com>
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In-Reply-To: <20250806195706.1650976-10-seanjc@google.com>

On Wed, Aug 06, 2025 at 12:56:31PM -0700, Sean Christopherson wrote:

> @@ -2727,6 +2739,21 @@ static struct pmu pmu = {
>  	.filter			= x86_pmu_filter,
>  };
>  
> +void arch_perf_load_guest_context(unsigned long data)
> +{
> +	u32 masked = data & APIC_LVT_MASKED;
> +
> +	apic_write(APIC_LVTPC,
> +		   APIC_DM_FIXED | PERF_GUEST_MEDIATED_PMI_VECTOR | masked);
> +	this_cpu_write(x86_guest_ctx_loaded, true);
> +}

I'm further confused, why would this ever be masked?