From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id DE4D0C5CFCF for ; Fri, 14 Aug 2026 05:18:40 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 6D4566B0616; Fri, 14 Aug 2026 01:18:39 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 664326B0617; Fri, 14 Aug 2026 01:18:39 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 54EC56B0618; Fri, 14 Aug 2026 01:18:39 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id 2AA446B0616 for ; Fri, 14 Aug 2026 01:18:39 -0400 (EDT) Received: from smtpin26.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay02.hostedemail.com (Postfix) with ESMTP id 7386712034A for ; Fri, 14 Aug 2026 05:18:38 +0000 (UTC) X-FDA: 85098719916.26.1CC6954 Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.16]) by imf10.hostedemail.com (Postfix) with ESMTP id 78F67C0002 for ; Fri, 14 Aug 2026 05:18:35 +0000 (UTC) Authentication-Results: imf10.hostedemail.com; dkim=pass header.d=intel.com header.s=Intel header.b=Fq9xTO1w; dmarc=pass (policy=none) header.from=intel.com; spf=pass (imf10.hostedemail.com: domain of binbin.wu@linux.intel.com designates 198.175.65.16 as permitted sender) smtp.mailfrom=binbin.wu@linux.intel.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1786684716; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=nh/q1cVILIwClSOSvbH2tQ1Kqv8X4RdrCPcUQHn8eSQ=; b=JGyUGdX2EZZ/bl6vw0MtHJI7wlUTBBNFsgNrIR+SwljgTnjnjHskOxoHncUBq/WQ0jk1gV qID7Lz9xCK+Dxusg9ayBXO2/1XPiyUQZOlUzDxw4BMiBZqSoihZ76m3KOGakggTQJWpXbL rsh4DGCnefLinR7+lx7X57CAv+w/3n8= ARC-Authentication-Results: i=1; imf10.hostedemail.com; dkim=pass header.d=intel.com header.s=Intel header.b=Fq9xTO1w; dmarc=pass (policy=none) header.from=intel.com; spf=pass (imf10.hostedemail.com: domain of binbin.wu@linux.intel.com designates 198.175.65.16 as permitted sender) smtp.mailfrom=binbin.wu@linux.intel.com ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1786684716; b=TsaIHkmZklOEOoQ2VvOyLNYoEt8fejtHbptsJfIjiZa5aG+DPiBIuCISL56chHxnTRHo1/ Oll5s819Ux70/6rFgR4PrhPcp+p4yKa8Md+HR/Z5XDNZ2Nrt8xI6yXrZJnEWmz2F1K3AZx 4FUk3xLWt24VsQcxhpQFz0R1muudccg= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1786684716; x=1818220716; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=+MUxfRWOkqREAuoekA780+CfxxKTEqlm5E/NKiwihFE=; b=Fq9xTO1wCx35Me5CWZnvAlS89GF8MFIiJGoH3Z2f5OrsOzPFfnrjylTo ZWuB/sVjw2sL9XkPx8Er8cS6QBOLluXwh+RWDK0yZG4t6H5wzRcyhhDi8 /LUxL+qvy1Se31i+47SBDqz3WUJFZMnc1ZgfDt1IcOleuruaJQxX0Zolr M15lVzggyhPltKXsTJg4xS+Dago3c1w9+DLSUorx3k22U0OumWE0oQxJV G/zYOPLG/ge6vJA32hC7SMM4/9lDDP0U3prP6V7ZLuQRu4+CTUm7fBu1V iyR3wHY9KhOOeoYbrbawXoBNp/O7DWZuXkjxcIXl4M70ydJtWlOUExiIp Q==; X-CSE-ConnectionGUID: CBtRoOWfS0mkc+kZJV71pA== X-CSE-MsgGUID: tIkHBGYXScmaJlCdm/6glg== X-IronPort-AV: E=McAfee;i="6800,10657,11874"; a="87481117" X-IronPort-AV: E=Sophos;i="6.25,222,1779174000"; d="scan'208";a="87481117" 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 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 X-Rspam-User: X-Rspamd-Queue-Id: 78F67C0002 X-Rspamd-Server: rspam07 X-Stat-Signature: nmc9i7kjqpeaztxmx7goryckcda18gi7 X-HE-Tag: 1786684715-526985 X-HE-Meta: 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 z2eJFj7W QXxp1+7hD396lfh3Wc6yDqguaDh7c6dyP99VpjjFFwPipKzI+NxM7JbJMVeaX7KMhRQuYJ5X3wvNRBsI5wKJjBxXzCL9rA2j7LC4YvxtcyfdrplmzYs+tup4pBtc2bwth6rDbbCv/1lR2H5YGHR+EyAJoTp9UZ0SjxhXrPhwlLouN5NBcY36MCs1xGcvekBX89ZKYnBIY2zhkSCq9WCb37o46Sz3uPdQ26Qs1Ea3h2YLsN0BPBX+dG3I2nujTPpTWmJUmp9nj35T8Sjz98czhncqgD3n/Cfgoa5NEZWXd5QilprTlZd6LmICTnSNwzw9DA1n9 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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); >