Received-SPF: pass (google.com: domain of linux-kernel+bounces-194696-linux.lists.archive=gmail.com@vger.kernel.org designates 147.75.48.161 as permitted sender) client-ip=147.75.48.161;
Message-ID: <ae870a38-e7ee-4334-ba4d-ca3e4e17a53d@zytor.com>
Date: Wed, 29 May 2024 14:12:19 -0700
Precedence: bulk
MIME-Version: 1.0
User-Agent: Mozilla Thunderbird
Subject: Re: [PATCH 4/6] x86/irq: Process nmi sources in NMI handler
To: Jacob Pan <jacob.jun.pan@linux.intel.com>, X86 Kernel <x86@kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Dave Hansen <dave.hansen@intel.com>, Ingo Molnar <mingo@redhat.com>,
        Borislav Petkov <bp@alien8.de>, linux-perf-users@vger.kernel.org,
        Peter Zijlstra <peterz@infradead.org>
Cc: Andi Kleen <andi.kleen@intel.com>, Xin Li <xin3.li@intel.com>
References: <20240529203325.3039243-1-jacob.jun.pan@linux.intel.com>
 <20240529203325.3039243-5-jacob.jun.pan@linux.intel.com>
Content-Language: en-US
From: "H. Peter Anvin" <hpa@zytor.com>
In-Reply-To: <20240529203325.3039243-5-jacob.jun.pan@linux.intel.com>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit

On 5/29/24 13:33, Jacob Pan wrote:
> +
> +	rcu_read_lock();
> +	/* Bit 0 is for unknown NMI sources, skip it. */
> +	for_each_set_bit_from(vec, &source_bitmask, NR_NMI_SOURCE_VECTORS) {
> +		a = rcu_dereference(nmiaction_src_table[vec]);
> +		if (!a) {
> +			pr_warn_ratelimited("NMI received %d no handler", vec);
> +			continue;
> +		}

In this case, you should assume some chipset hardware or VMM is giving 
you garbage in the event bitmask, and treat it as if bit 0 were set.

	-hpa