From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.16]) (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 865F8346A04; Fri, 14 Aug 2026 05:18:34 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.175.65.16 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786684717; cv=none; b=omiDrswumaSrjXLBoPBlQKC1QQyFg9LFdHv9DxmfjneJwHH8Pt/SLpFWV/hpDW2phLDa/oFgT7fRKorrg5wKTszsT5ItHEIvzVqx3EB1+i3LNBmLdMjlVhwTYaBZIrAzKid3KW+APknNK5K3QPmNXwJl8G5O56xBud1R87ZPA8c= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786684717; c=relaxed/simple; bh=+MUxfRWOkqREAuoekA780+CfxxKTEqlm5E/NKiwihFE=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=EqP04Dc8rKKALwPXMed/HPrSR7MmaRdN86c/QccuQzeEm1MUCYdh2vxkSvmP4mq2PxKAyUGIxW/q2oifs1teLhlEp2Hjwtf/ENHoeuD+T9JxA67e9cuJSoA7AcEEbP3bc0Nn8oXkp+LNXf4DCXRk09M4zbrEHGRKJ8f8tV/cXKw= 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=P1kHph+z; arc=none smtp.client-ip=198.175.65.16 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="P1kHph+z" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1786684715; x=1818220715; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=+MUxfRWOkqREAuoekA780+CfxxKTEqlm5E/NKiwihFE=; b=P1kHph+zrCFpTLxg8CIkAkdkjhiuKSHXRCYAK7lTE1/8HU0mB3OVubg1 2BAytgo0YmAoX+4n5xlaij/qwnDx4IryD0Ek9UF0G6KWfHYT+H8IjLDPH FKjUzluaZ5kbA9cMujrKMwoZQ2P/yv8t7Y+28wvFaYI+VwOIPX5GZxkwI gW4+53d/MqJCRuTXV4B7yjUGbFvhDXz3rRoiLYoPtmuse4JjeTqRzRoOG 4mOGkwwf0/SD65ZExxbTNOr2+q9UtUlXrdxHPLg9VpxJWXWp8iIRv6Aof /cSEp+j909mfj7JlnI7TIUJDAKbK8BRMn4mir1HlY4+BLfs21mAUs1W5I w==; X-CSE-ConnectionGUID: Z3Veuck/TZeR6EpD4DSAaw== X-CSE-MsgGUID: 5M++MCpnSomnIdFo8yQZsQ== X-IronPort-AV: E=McAfee;i="6800,10657,11874"; a="87481113" X-IronPort-AV: E=Sophos;i="6.25,222,1779174000"; d="scan'208";a="87481113" Received: from fmviesa004.fm.intel.com ([10.60.135.144]) by orvoesa108.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 13 Aug 2026 22:18:34 -0700 X-CSE-ConnectionGUID: IN/b0L//SVCz/TGsloL3PQ== X-CSE-MsgGUID: VWlRvfb+T1OqDKsfu60fhQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.25,222,1779174000"; d="scan'208";a="266117899" Received: from binbinwu-mobl.ccr.corp.intel.com (HELO [10.124.245.162]) ([10.124.245.162]) by fmviesa004-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 13 Aug 2026 22:18:20 -0700 Message-ID: <645af2bd-2791-473a-9441-40db01f58913@linux.intel.com> Date: Fri, 14 Aug 2026 13:18:17 +0800 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 v10 16/41] KVM: guest_memfd: Zero page while getting pfn 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, 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 , 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, 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, Xiaoyao Li References: <20260807-gmem-inplace-conversion-v10-0-2fc18ee6d3ba@google.com> <20260807-gmem-inplace-conversion-v10-16-2fc18ee6d3ba@google.com> Content-Language: en-US From: Binbin Wu In-Reply-To: <20260807-gmem-inplace-conversion-v10-16-2fc18ee6d3ba@google.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 8/8/2026 5:52 AM, Ackerley Tng via B4 Relay wrote: > From: Ackerley Tng > > Move the folio initialization logic from kvm_gmem_get_pfn() into > __kvm_gmem_get_pfn() to also zero pages if the page is to be used in > kvm_gmem_populate(). > > With in-place conversion, the existing data in a guest_memfd page can be > populated into guest memory through platform-specific ioctls. > > Without first zeroing the page obtained using __kvm_gmem_get_pfn(), it > might contain uninitialized host memory, which would leak to the guest if > the populate completes. > > guest_memfd pages are zeroed at most once in the page's entire lifetime > with guest_memfd, and that is tracked using the uptodate flag. > > Zeroing the page in __kvm_gmem_get_pfn() is chosen over zeroing in > kvm_gmem_get_folio() since other flows, such as a future write() syscall, > can get a page, write to the page and then set page uptodate without > zeroing. > > This aligns with the concept of zeroing before first use - the other place > where zeroing happens is in kvm_gmem_fault_user_mapping(). > > Don't mark the page uptodate again after populating, since the page would > already be marked uptodate before the post_populate() call. > > Reviewed-by: Fuad Tabba > Tested-by: Shivank Garg > Reviewed-by: Xiaoyao Li > Signed-off-by: Ackerley Tng Reviewed-by: Binbin Wu > --- > virt/kvm/guest_memfd.c | 12 +++++------- > 1 file changed, 5 insertions(+), 7 deletions(-) > > diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c > index 030af0855f8b0..41950c8105b5d 100644 > --- a/virt/kvm/guest_memfd.c > +++ b/virt/kvm/guest_memfd.c > @@ -1079,6 +1079,11 @@ static struct folio *__kvm_gmem_get_pfn(struct file *file, > return ERR_PTR(-EHWPOISON); > } > > + if (!folio_test_uptodate(folio)) { > + clear_highpage(folio_page(folio, 0)); > + folio_mark_uptodate(folio); > + } > + > *pfn = folio_file_pfn(folio, index); > if (max_order) > *max_order = 0; > @@ -1108,11 +1113,6 @@ int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot, > goto out; > } > > - if (!folio_test_uptodate(folio)) { > - clear_highpage(folio_page(folio, 0)); > - folio_mark_uptodate(folio); > - } > - > #ifdef CONFIG_HAVE_KVM_ARCH_GMEM_CONVERT > if (kvm_gmem_is_private_mem(file_inode(file), index)) > r = kvm_arch_gmem_make_private(kvm, gfn, *pfn, > @@ -1159,8 +1159,6 @@ static long __kvm_gmem_populate(struct kvm *kvm, struct kvm_memory_slot *slot, > } > > ret = post_populate(kvm, gfn, pfn, src_page, opaque); > - if (!ret) > - folio_mark_uptodate(folio); > > out_put_folio: > folio_put(folio); >