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X-CSE-ConnectionGUID: sWJ4VUm4S4eqy+Glz5JkTQ== X-CSE-MsgGUID: nLmW+nz/SHOeph227Z/yqQ== X-IronPort-AV: E=McAfee;i="6800,10657,11866"; a="85691173" X-IronPort-AV: E=Sophos;i="6.25,207,1779174000"; d="scan'208";a="85691173" Received: from orviesa006.jf.intel.com ([10.64.159.146]) by fmvoesa112.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 05 Aug 2026 18:41:16 -0700 X-CSE-ConnectionGUID: 5oIPZ2NyTCqHZV8yl6Tp9w== X-CSE-MsgGUID: x7bSvlzdSNGXBVIWi4OGbg== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.25,207,1779174000"; d="scan'208";a="260186253" Received: from fuxiaogu-mobl1.ccr.corp.intel.com (HELO [10.238.208.47]) ([10.238.208.47]) by orviesa006-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 05 Aug 2026 18:41:01 -0700 Message-ID: Date: Thu, 6 Aug 2026 09:40:58 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v9 03/41] KVM: Enumerate support for PRIVATE memory iff kvm_arch_has_private_mem is defined To: Sean Christopherson Cc: Ackerley Tng , 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, tabba@google.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 , 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 , Vlastimil Babka , 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: <20260728-gmem-inplace-conversion-v9-0-35f9aec2aed2@google.com> <20260728-gmem-inplace-conversion-v9-3-35f9aec2aed2@google.com> <7dafaa90-f3d4-4be4-a5cc-472163f18040@intel.com> Content-Language: en-US From: Xiaoyao Li In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 396CD14000F X-Stat-Signature: x7i5gcnz8udikbctarkjr1hjeukqs3ss X-HE-Tag: 1785980477-551685 X-HE-Meta: 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 8KVY3jKg xsioXw+NR6tC8Bm7t9U3cS4RLJKGb0jnMuiLf0f9wTD8AhLJy16qwr6F389Ys3/7N0wRluQk3g3rdQTTQkeFMeUn3RVtW6Zuic4jCpnL6pJssZzNjOf2QNwjTRxtoMWZxofyAmznS+D1cXJrFBJExhfur2izDaRyvNQclCAykNvO5tBUDKLZEH9GpJcrA639uyuIC0dKcMsyDuNJgX4+63uRRunKDKp8mkxvfjq8soYO4S9kotP8YEEr9K7DL01A/QAjr Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 8/6/2026 8:43 AM, Sean Christopherson wrote: > On Wed, Aug 05, 2026, Xiaoyao Li wrote: >> On 7/31/2026 4:34 AM, Ackerley Tng wrote: >>> I think another way to phrase this is that if we don't make this change, >>> say, on the foo architecture where there's no CoCo and no private mem >>> support, kvm_supported_mem_attributes() would return true for the !kvm >>> case, which is over-reporting. >> >> Under the condition that the foo architecture enables >> CONFIG_KVM_VM_MEMORY_ATTRIBUTES. >> >>> How about this, replacing the entire changelog paragraph above: >>> >>> Explicitly guard reporting support for KVM_MEMORY_ATTRIBUTE_PRIVATE >>> based on kvm_arch_has_private_mem being #defined. This improves >>> reporting accuracy by not reporting support for >>> KVM_MEMORY_ATTRIBUTE_PRIVATE when kvm_supported_mem_attributes() is >>> called with kvm == NULL. >> >> It doesn't help for the case where kvm == NULL, but help for the case where >> CONFIG_KVM_VM_MEMORY_ATTRIBUTES is defined but kvm_arch_has_private_mem not. >> >> sorry for being picky. I think we can say >> >> This improves the reporting accuracy by avoiding the case where >> KVM_MEMORY_ATTRIBUTE_PRIVATE is reported when kvm == null even without >> kvm_arch_has_private_mem being #defined. > > How about this? > > Explicitly guard reporting support for KVM_MEMORY_ATTRIBUTE_PRIVATE based > on kvm_arch_has_private_mem being #defined in anticipation of tracking > PRIVATE vs. SHARED state per-guest_memfd, not per-VM (to allow in-place > conversion). Sorry, maybe I'm stupid. I still don't understand how to connect it to tracking PRIVATE vs. SHARED state per-guest_memfd. There are two diffs in this patch, and we are talking about the second diff, right? If the kvm_supported_mem_attributes() will be used by gmem, I can buy the justification. But it won't. At least, it won't after this series. > guest_memfd support for memory attributes is expected to be unconditional > to avoid yet more macros (all architectures that support guest_memfd are > expected to use per-gmem attributes at some point), at which point > enumerating support KVM_MEMORY_ATTRIBUTE_PRIVATE based solely on memory > attributes being supported by KVM at-large would result in a system-scope s/memory attributes/CONFIG_KVM_VM_MEMORY_ATTRIBUTES/ ? > check (NULL @kvm) over-reporting support on arm64. I think arm64 won't define CONFIG_KVM_VM_MEMORY_ATTRIBUTES? So it seems to have nothing to do with arm64. It matters for x86. After patch 20, CONFIG_KVM_VM_MEMORY_ATTRIBUTES is user-configurable. At that time, people can disable CONFIG_KVM_SW_PROTECTED_VM, CONFIG_KVM_INTEL_TDX and CONFIG_KVM_AMD_SEV, but enable CONFIG_KVM_VM_MEMORY_ATTRIBUTES on x86. In this case, kvm_supported_mem_attributes() reports KVM_MEMORY_ATTRIBUTE_PRIVATE for system-scope query which is totally wrong. I think this is the case we want to prevent not something won't happen for arm64? >> >>> Give architectures full control over overriding the default definition >>> of kvm_arch_has_private_mem() by removing the coupling with >>> CONFIG_KVM_VM_MEMORY_ATTRIBUTES. >>> >>> In a later patch, kvm_arch_has_private_mem() will be defined based on >>> whether architectural features are compiled in, and made orthogonal to >>> CONFIG_KVM_VM_MEMORY_ATTRIBUTES. >>