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X-CSE-ConnectionGUID: 2cUCyCMNR6O7o42J/U6z7g== X-CSE-MsgGUID: 3+Iht4LHR/WUhH96KUsVbw== X-IronPort-AV: E=McAfee;i="6800,10657,11901"; a="89450922" X-IronPort-AV: E=Sophos;i="6.27,97,1787036400"; d="scan'208";a="89450922" Received: from fmviesa013.fm.intel.com ([10.60.135.153]) by fmvoesa111.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 Sep 2026 02:18:11 -0700 X-CSE-ConnectionGUID: LGX/EWeHSPeVzgyLApP5NA== X-CSE-MsgGUID: IuTtAxozTIW46d9/CqObww== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.27,97,1787036400"; d="scan'208";a="238127" Received: from xiaoyaol-hp-g830.ccr.corp.intel.com (HELO [10.124.240.119]) ([10.124.240.119]) by smtpauth.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 Sep 2026 02:17:54 -0700 Message-ID: <9eee9ca8-3818-435f-ae09-78b241050e9e@intel.com> Date: Fri, 11 Sep 2026 17:17:51 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v13 01/44] KVM: guest_memfd: Optimize away conversion overheads via dead-code elimination To: ackerleytng@google.com, aik@amd.com, andrew.jones@linux.dev, binbin.wu@linux.intel.com, brauner@kernel.org, chao.p.peng@linux.intel.com, david@kernel.org, jmattson@google.com, jthoughton@google.com, michael.roth@amd.com, oupton@kernel.org, pankaj.gupta@amd.com, qperret@google.com, rick.p.edgecombe@intel.com, rientjes@google.com, shivankg@amd.com, steven.price@arm.com, willy@infradead.org, wyihan@google.com, yan.y.zhao@intel.com, forkloop@google.com, pratyush@kernel.org, suzuki.poulose@arm.com, aneesh.kumar@kernel.org, liam@infradead.org, Paolo Bonzini , Sean Christopherson , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , Jonathan Corbet , Shuah Khan , Shuah Khan , Vishal Annapurve , Andrew Morton , Chris Li , Kairui Song , Kemeng Shi , Nhat Pham , Barry Song , Axel Rasmussen , Yuanchu Xie , Wei Xu , Youngjun Park , Qi Zheng , Shakeel Butt , Kiryl Shutsemau , Baoquan He , Jason Gunthorpe , John Hubbard , Peter Xu , tarunsahu@google.com, Randy Dunlap , Lorenzo Stoakes , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Fuad Tabba Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mm@kvack.org, linux-coco@lists.linux.dev References: <20260910-gmem-inplace-conversion-v13-0-dd6fbf94f4e1@google.com> <20260910-gmem-inplace-conversion-v13-1-dd6fbf94f4e1@google.com> Content-Language: en-US From: Xiaoyao Li In-Reply-To: <20260910-gmem-inplace-conversion-v13-1-dd6fbf94f4e1@google.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: BA4B420004 X-Rspam-User: X-Stat-Signature: su4ppf355sbud51hmpjrqnm5jzue4utq X-HE-Tag: 1789118292-423897 X-HE-Meta: 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 duJ+qycP vhtidhfgT4nZLtMi6+XAfXz8nso36Ijzm0SwAKpvQTcHqpu/RvuyzoevdDwoxuh1eSr9SpmzHqRcoPMNjzKoEaXMEX3sCUBXQXwba8XS3xYsKtilDjrE81mTUKycoFaM9X+335meNjD0DIWdAkTZNwdByGvQ3XSyeP/oYQE94p62yqyj+ZbDDp5h93KX4h8AW9yuU4LSEQsEI98E+1l1jQ+swePw36N0An9hMEwgODmAluiwidWQybmLDWJoA7FBwSMwla0fLs5WPuzPRzhLL72WJsydRu1wNMqAD1kZsBIt6ba4C16Wj+y545SUfX34mDeaY Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 9/11/2026 7:55 AM, Ackerley Tng via B4 Relay wrote: > From: Sean Christopherson > > Add and use kvm_arch_has_gmem_convert() to guard guest_memfd's invocation > of arch hooks related to converting memory between private and shared, as > only one half of the x86 CoCo duo needs the runtime hooks (any pre-work is > pure overhead for TDX). At this exact moment, the overhead is negligible, > but that will change when in-place conversion comes along, at which point > to-shared conversions will "need" to find all affected folios prior to > calling into arch code. In quotes because very technically that work could > be pushed to arch code, but that would bleed guest_memfd details into arch > code and would be far worse than adding yet another kvm_arch_has... hook. > > Opportunistically provide the kvm_arch_gmem_make_private() declaration, and > rely on dead-code elimination to eliminate the call to non-existent code > when CONFIG_HAVE_KVM_ARCH_GMEM_CONVERT=n. > > Reported-by: Binbin Wu > Closes: https://lore.kernel.org/all/1ec08cd8-3072-4753-ad5e-cd34956647f8@linux.intel.com > Suggested-by: Ackerley Tng > Signed-off-by: Sean Christopherson > Signed-off-by: Ackerley Tng > Reviewed-by: Fuad Tabba > Reviewed-by: Binbin Wu > Reviewed-by: David Hildenbrand (Arm) Reviewed-by: Xiaoyao Li