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X-CSE-ConnectionGUID: JXMrVUoOSSWWULYx09U+xA== X-CSE-MsgGUID: mbg4zSpIQPqLlbG0wvQxbQ== X-IronPort-AV: E=McAfee;i="6600,9927,11069"; a="11534169" X-IronPort-AV: E=Sophos;i="6.08,151,1712646000"; d="scan'208";a="11534169" Received: from fmviesa008.fm.intel.com ([10.60.135.148]) by fmvoesa109.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 10 May 2024 12:48:18 -0700 X-CSE-ConnectionGUID: f/ugZBk2QXGZrOQ7kSzH3w== X-CSE-MsgGUID: UkmdNvhORKeQLtMkM2bQlQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.08,151,1712646000"; d="scan'208";a="29662577" Received: from viggo.jf.intel.com (HELO [127.0.0.1]) ([10.54.77.144]) by fmviesa008.fm.intel.com with ESMTP; 10 May 2024 12:48:15 -0700 Message-ID: Date: Fri, 10 May 2024 12:48:15 -0700 Precedence: bulk X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/1] x86/vector: Fix vector leak during CPU offline To: Dongli Zhang , x86@kernel.org Cc: tglx@linutronix.de, mingo@redhat.com, Borislavbp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com, joe.jin@oracle.com, linux-kernel@vger.kernel.org, virtualization@lists.linux.dev References: <20240510190623.117031-1-dongli.zhang@oracle.com> From: Dave Hansen Content-Language: en-US Autocrypt: addr=dave.hansen@linux.intel.com; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 5/10/24 12:06, Dongli Zhang wrote: > } else { > + /* > + * This call borrows from the comments and implementation > + * of apic_update_vector(): "If the target CPU is offline > + * then the regular release mechanism via the cleanup > + * vector is not possible and the vector can be immediately > + * freed in the underlying matrix allocator.". > + */ > + irq_matrix_free(vector_matrix, apicd->prev_cpu, > + apicd->prev_vector, apicd->is_managed); > apicd->prev_vector = 0; > } I know it's just two sites, but I'd much rather spend the space on a helper function than a copy-and-pasted comment. Wouldn't something like this make it like stupidly obvious what's going on: if (cpu_online(cpu)) { ... } else { irq_matrix_free_offline(apicd->prev_cpu, apicd->prev_vector, apicd->is_managed); apicd->prev_vector = 0; } /* Free a vector when the target CPU is offline */ static void irq_matrix_free_offline(...) { lockdep_assert_held(&vector_lock); WARN_ON_ONCE(!cpu_offline(apicd->prev_cpu)); /* * The regular release mechanism via the cleanup vector is not * possible. Immediately free the vector in the underlying * matrix allocator. */ irq_matrix_free(&whatever, cpu, vector, managed); } It would also be rather hard to screw up even if someone called it on an online CPU because you'd get a nice warning.