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X-CSE-ConnectionGUID: flnenzddRdWKjBZQj9bLrQ== X-CSE-MsgGUID: xtVG4SebSzCbs/091eMh7w== X-IronPort-AV: E=McAfee;i="6800,10657,11705"; a="72415798" X-IronPort-AV: E=Sophos;i="6.21,298,1763452800"; d="scan'208";a="72415798" Received: from orviesa004.jf.intel.com ([10.64.159.144]) by fmvoesa111.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 18 Feb 2026 06:59:39 -0800 X-CSE-ConnectionGUID: 14Hwz+PuSA6YNrMDw9Qzmg== X-CSE-MsgGUID: 0w75jjLuRhuudalHmr5PeA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.21,298,1763452800"; d="scan'208";a="218737003" Received: from rchatre-mobl4.amr.corp.intel.com (HELO [10.125.109.189]) ([10.125.109.189]) by orviesa004-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 18 Feb 2026 06:59:38 -0800 Message-ID: <59c0b0f0-26b0-4311-82a9-a5f8392ec4c6@intel.com> Date: Wed, 18 Feb 2026 06:59:37 -0800 Precedence: bulk X-Mailing-List: linux-coco@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 2/6] x86/sev: add support for enabling RMPOPT To: K Prateek Nayak , Ashish Kalra , tglx@kernel.org, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, seanjc@google.com, peterz@infradead.org, thomas.lendacky@amd.com, herbert@gondor.apana.org.au, davem@davemloft.net, ardb@kernel.org Cc: pbonzini@redhat.com, aik@amd.com, Michael.Roth@amd.com, Tycho.Andersen@amd.com, Nathan.Fontenot@amd.com, jackyli@google.com, pgonda@google.com, rientjes@google.com, jacobhxu@google.com, xin@zytor.com, pawan.kumar.gupta@linux.intel.com, babu.moger@amd.com, dyoung@redhat.com, nikunj@amd.com, john.allen@amd.com, darwi@linutronix.de, linux-kernel@vger.kernel.org, linux-crypto@vger.kernel.org, kvm@vger.kernel.org, linux-coco@lists.linux.dev References: <7df872903e16ccee9fce73b34280ede8dfc37063.1771321114.git.ashish.kalra@amd.com> <10baddd3-add6-4771-a1ce-f759d3ec69d2@intel.com> From: Dave Hansen Content-Language: en-US Autocrypt: addr=dave.hansen@intel.com; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 2/17/26 19:08, K Prateek Nayak wrote: > Hello Dave, > > On 2/18/2026 3:36 AM, Dave Hansen wrote: >>> +/* >>> + * Build a cpumask of online primary threads, accounting for primary threads >>> + * that have been offlined while their secondary threads are still online. >>> + */ >>> +static void get_cpumask_of_primary_threads(cpumask_var_t cpulist) >>> +{ >>> + cpumask_t cpus; >>> + int cpu; >>> + >>> + cpumask_copy(&cpus, cpu_online_mask); >>> + for_each_cpu(cpu, &cpus) { >>> + cpumask_set_cpu(cpu, cpulist); >>> + cpumask_andnot(&cpus, &cpus, cpu_smt_mask(cpu)); >>> + } >>> +} >> >> Don't we have a primary thread mask already? I thought we did. > > If you are referring to cpu_primary_thread_mask(), the CPUs are set on it > based on the LSB of APICID, specifically: > > !(apicid & (__max_threads_per_core - 1)) > > It can so happen, the primary thread ((apicid & 1) == 0) of the core is > offline while the secondary thread ((apicid & 1) == 1) is online but the > traversal of (cpu_primary_thread_mask() & cpu_online_mask()) will simply > skip these cores. > > Is there an equivalent mask that sets the first online CPU of each core? No I don't think we have that sitting around. But, stepping back, why is this even necessary? Is it just saving a few IPIs in the super rare case that someone has offlined the primary thread but not a secondary one? Why bother?