From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.14]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6C39243A7E7 for ; Tue, 1 Sep 2026 09:47:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.175.65.14 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788256078; cv=none; b=dteLoHqavcsfKUuHsUWzaOO/FlAZWUAyBxtCwoKLFE9ZpoVly29HIfKrPaeEPJ2IM1WrRwe2X1f4EJ9+oFA0wQrRPTG5BXeTAtSg65SJR85j+5phvogyeUIRKMkzN9veOUqFz4jNPQ759i/nySXsOKhjtEYzHc/V+Q4vsjjW5K0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788256078; c=relaxed/simple; bh=PqWpX5qzfJy+A/rydNLTfBbEMaehm3F4tTQxb73Ubm0=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=GQ+ks+orS6xpm24IBBYzJgli85o/7JIITN2+O5I+k82h2E8GdxCsD+hMaGb/xUzskamtBcBPFuY3fQNpWnhx9wUwTPua+kWSh1rXByj1ki3CeFXD7Bl1X2vRAiOqTDt481wNFta+sXR0i64H0egF19goM59Ylh1AVcrqojjd74c= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com; spf=pass smtp.mailfrom=linux.intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=IPtnMNmE; arc=none smtp.client-ip=198.175.65.14 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="IPtnMNmE" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1788256076; x=1819792076; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=PqWpX5qzfJy+A/rydNLTfBbEMaehm3F4tTQxb73Ubm0=; b=IPtnMNmERpOYan1GIQ0aFoihWxjM3PDlQM6DdxjRSFBxq3eoxIVfeE8V gO8o75npcz96Diy0aZRrOd2tptG9dBI/Ep2XuCHMmaP4BCGz+M9OUQngN vXUU3ZhlnAQi0QKI3kTMr3Dvdl/KcArsjQKGKuDGfC6VdVHmsZnszVeu/ WZ8uCxwzafLyh5QOl4RFMxD4H5vtipCpnTlN43ojhu/mFbVYRtT/0tpSt uEeeT0MLuIOfxQBMAs1mwFY4j57COiurdpFCjIkVFIRF59ZTCGmjN1aRo 7irLY4pQrJHjt7Wdf5G/iOJxj/+Prb/LTY7ReZ+nf2FpaDn9nvFkLTFLY w==; X-CSE-ConnectionGUID: v/Iwp8A/SS2qNfnRNr68ZQ== X-CSE-MsgGUID: NSrB3ID5SWCc/lq/I+uCJA== X-IronPort-AV: E=McAfee;i="6800,10657,11892"; a="92546880" X-IronPort-AV: E=Sophos;i="6.25,255,1779174000"; d="scan'208";a="92546880" Received: from orviesa001.jf.intel.com ([10.64.159.141]) by orvoesa106.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 01 Sep 2026 02:47:54 -0700 X-CSE-ConnectionGUID: fV2Zhz8TSAW2Arb2x6ej0w== X-CSE-MsgGUID: 2maLF6D4Rr6e+knV4AZ/ug== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.25,255,1779174000"; d="scan'208";a="307263818" Received: from unknown (HELO [10.238.2.33]) ([10.238.2.33]) by smtpauth.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 01 Sep 2026 02:47:40 -0700 Message-ID: Date: Tue, 1 Sep 2026 17:47:37 +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 v12 09/45] KVM: guest_memfd: Stub in ability to enable in-place shared<=>private conversion To: ackerleytng@google.com Cc: aik@amd.com, andrew.jones@linux.dev, 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 , 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, Xiaoyao Li References: <20260830-gmem-inplace-conversion-v12-0-85e5fd25252a@google.com> <20260830-gmem-inplace-conversion-v12-9-85e5fd25252a@google.com> Content-Language: en-US From: Binbin Wu In-Reply-To: <20260830-gmem-inplace-conversion-v12-9-85e5fd25252a@google.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 8/31/2026 8:25 AM, Ackerley Tng via B4 Relay wrote: > From: Sean Christopherson > > Stub in global variable to enable in-place guest_memfd private<=>shared > memory conversion, which will eventually be exposed to userspace via a > module param, and wire up the __kvm_is_private_gfn() static call to the > guest_memfd version when in-place conversion is enabled, i.e. when gmem is > the sole authority on private vs. shared memory. > > Cc: Fuad Tabba > Cc: Xiaoyao Li > Signed-off-by: Sean Christopherson > Co-developed-by: Ackerley Tng > Signed-off-by: Ackerley Tng Reviewed-by: Binbin Wu One nit below. > --- > Documentation/virt/kvm/api.rst | 7 +++++++ > include/linux/kvm_host.h | 6 ++++++ > virt/kvm/guest_memfd.c | 26 ++++++++++++++++++++++++++ > virt/kvm/kvm_main.c | 12 +++++++++++- > 4 files changed, 50 insertions(+), 1 deletion(-) > > diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst > index e0430cc750c9e..90a29424c54c8 100644 > --- a/Documentation/virt/kvm/api.rst > +++ b/Documentation/virt/kvm/api.rst > @@ -6382,6 +6382,11 @@ KVM_SET_USER_MEMORY_REGION2, e.g. shared memory can be lazily mapped/allocated > on-demand. > > When mapping a gfn into the guest, KVM selects shared vs. private, i.e consumes > +userspace_addr vs. guest_memfd, based on the state in guest_memfd, which is the > +sole authority on private vs. shared memory. See :ref:`KVM_CREATE_GUEST_MEMFD` > +to find out more about the creation-time shared/private status. > + > +If in-place conversion is disabled, KVM selects shared vs. private, i.e consumes Nit: i.e -> i.e. > userspace_addr vs. guest_memfd, based on the gfn's KVM_MEMORY_ATTRIBUTE_PRIVATE > state. At VM creation time, all memory is shared, i.e. the PRIVATE attribute > is '0' for all gfns. Userspace can control whether memory is shared/private by > @@ -6429,6 +6434,8 @@ the state of a gfn/page as needed. >