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X-CSE-ConnectionGUID: p1uUIVA+SN2krwJbBMDWBQ== X-CSE-MsgGUID: UdilRn9rSHeXq2FqzvaQfg== X-IronPort-AV: E=McAfee;i="6800,10657,11717"; a="98987231" X-IronPort-AV: E=Sophos;i="6.21,320,1763452800"; d="scan'208";a="98987231" Received: from orviesa010.jf.intel.com ([10.64.159.150]) by fmvoesa101.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 02 Mar 2026 15:00:04 -0800 X-CSE-ConnectionGUID: 4JVBorZgRlexv62icekUVg== X-CSE-MsgGUID: eUSFDL7BRZaH7/SLv0QQMQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.21,320,1763452800"; d="scan'208";a="217034536" Received: from cmdeoliv-mobl4.amr.corp.intel.com (HELO [10.125.108.103]) ([10.125.108.103]) by orviesa010-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 02 Mar 2026 15:00:03 -0800 Message-ID: <86bcca73-0c1b-405f-a72d-debb3c696333@intel.com> Date: Mon, 2 Mar 2026 15:00:08 -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 v2 2/7] x86/sev: add support for enabling RMPOPT To: "Kalra, Ashish" , 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, KPrateek.Nayak@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: <85aec55af41957678d214e9629eb6249b064fa87.1772486459.git.ashish.kalra@amd.com> <6a50d050-f602-43fd-a44a-cecedd9823eb@amd.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 3/2/26 14:55, Kalra, Ashish wrote: >> What's wrong with: >> >> u64 rmpopt_base = pa_start | MSR_AMD64_RMPOPT_ENABLE; >> ... >> for_each_online_cpu(cpu) >> wrmsrq_on_cpu(cpu, MSR_AMD64_RMPOPT_BASE, rmpopt_base); >> >> Then there's at least no ugly casting. >> > RMOPT_BASE MSRs don't need to be set serially, therefore, by > using the cpu_online_mask and on_each_cpu_mask(), we can setup the MSRs > concurrently and in parallel. Using for_each_online_cpu() will be slower than > doing on_each_cpu_mask() as it doesn't send IPIs in parallel, right. If that's the case and you *need* performance, then please go add a wrmsrq_on_cpumask() function to do things in parallel.