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X-CSE-ConnectionGUID: rJnitn9hTseJzHicO4z+pg== X-CSE-MsgGUID: Kifo8ESiSk6j0t5Ijaea2w== X-IronPort-AV: E=McAfee;i="6800,10657,11744"; a="75090542" X-IronPort-AV: E=Sophos;i="6.23,150,1770624000"; d="scan'208";a="75090542" Received: from orviesa008.jf.intel.com ([10.64.159.148]) by fmvoesa112.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 30 Mar 2026 16:47:22 -0700 X-CSE-ConnectionGUID: 8VtA7xPBQV6oAIMsJ0kXVA== X-CSE-MsgGUID: mw3vnuuIRWG7PJAvdjWMlA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.23,150,1770624000"; d="scan'208";a="226169255" Received: from schen9-mobl4.amr.corp.intel.com (HELO [10.125.111.27]) ([10.125.111.27]) by orviesa008-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 30 Mar 2026 16:47:21 -0700 Message-ID: Date: Mon, 30 Mar 2026 16:47:27 -0700 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 5/6] KVM: SEV: Perform RMP optimizations on SNP guest shutdown To: 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, 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: Content-Language: en-US From: Dave Hansen Autocrypt: addr=dave.hansen@intel.com; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 3/30/26 15:27, Ashish Kalra wrote: > From: Ashish Kalra > > As SNP guests are launched, pages converted to private cause RMPUPDATE > to disable the corresponding RMPOPT optimizations. > > Conversely, during SNP guest termination, when guest pages are > converted back to shared and are not assigned, RMPOPT will be used > to re-enable RMP optimizations. This is all super passive. It makes it impossible to tell what is background versus imperative voice on what the patch is doing. == Background / Problem == Pages are converted from shared to private as SNP guests are launched. This destroys existing RMPOPT optimizations in the regions where pages are converted. Conversely, guest pages are converted back to shared during SNP guest termination and their region may become eligible for RMPOPT optimization. == Solution == To take advantage of this, perform RMPOPT after guest termination. Do it after a delay so that a single RMPOPT pass can be done if multiple guests terminate in a short period of time. With a fixed changelog: Acked-by: Dave Hansen I'm just saying "ack" on this one because it's a pretty KVM-specific thing about when the guest is destroyed to the point of being good for RMPOPT. This needs many more eyeballs from the KVM folks than me.