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 0F3D410FCAEA for ; Wed, 1 Apr 2026 21:43:51 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id EDE536B0088; Wed, 1 Apr 2026 17:43:50 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id E8F296B0089; Wed, 1 Apr 2026 17:43:50 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id D7DBA6B008A; Wed, 1 Apr 2026 17:43:50 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id C5E5B6B0088 for ; Wed, 1 Apr 2026 17:43:50 -0400 (EDT) Received: from smtpin02.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id 63C4D1B70CB for ; Wed, 1 Apr 2026 21:43:50 +0000 (UTC) X-FDA: 84611314620.02.44A431F Received: from mail-ua1-f54.google.com (mail-ua1-f54.google.com [209.85.222.54]) by imf11.hostedemail.com (Postfix) with ESMTP id 4EF1540017 for ; Wed, 1 Apr 2026 21:43:48 +0000 (UTC) Authentication-Results: imf11.hostedemail.com; dkim=pass header.d=google.com header.s=20251104 header.b=AcdV4d3j; arc=pass ("google.com:s=arc-20240605:i=1"); spf=pass (imf11.hostedemail.com: domain of ackerleytng@google.com designates 209.85.222.54 as permitted sender) smtp.mailfrom=ackerleytng@google.com; dmarc=pass (policy=reject) header.from=google.com ARC-Message-Signature: i=2; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1775079828; 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: in-reply-to:in-reply-to:references:references:dkim-signature; bh=1YVI0hayK/pE2zwI/10lFSwnfbjn36xvcFyuXZ+58V8=; b=eYcA2ziAZ5CV4jBz3DqerqKtTOoztCIVTlXscB84go1i+P4+FqJh6YrklVhix4BIkk+EkT 2xJAY7kL1eIx6yCoFt1n+jVujOWOKSWpj8YA5hTkGAFu+WGKPeP0sUVQn3BXKhWZcuB7VG pN4bYun7BkdG42sCOIUAiH03sb5IRuE= ARC-Seal: i=2; s=arc-20220608; d=hostedemail.com; t=1775079828; a=rsa-sha256; cv=pass; b=uALqipBCjFKOmJ2qlwU08E6UO7fAShZDJsnb3arIQNzmHoiAVYMN9wIW5/E9b5lvuA2ZGI IIuk4FXMiAnwHLH3KqTDvBhKlcMe+naY1PzxzPcQf4Vogx3Y7rA6UWOBFJgw06nAzCwTmf vtyV3JoLFfyRXNlI9HiaSLJ5L8eGWVE= ARC-Authentication-Results: i=2; imf11.hostedemail.com; dkim=pass header.d=google.com header.s=20251104 header.b=AcdV4d3j; arc=pass ("google.com:s=arc-20240605:i=1"); spf=pass (imf11.hostedemail.com: domain of ackerleytng@google.com designates 209.85.222.54 as permitted sender) smtp.mailfrom=ackerleytng@google.com; dmarc=pass (policy=reject) header.from=google.com Received: by mail-ua1-f54.google.com with SMTP id a1e0cc1a2514c-953b7d2c820so78563241.3 for ; Wed, 01 Apr 2026 14:43:48 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1775079827; cv=none; d=google.com; s=arc-20240605; b=AxRcdwq8VWj76ubPHSgl55UMQwXeQ/NyIquMjQwRzqJFk5gwCkMENFkas3+fIA8wOi 9gViVNAsKB9MEOvr9PjEm1iXVy8R5rOS2P8/SjqthZyAcA5MuU5QGDNN/4jRQa4mhyM7 W/mY8mdaHmyx/4TsNlm/ChaeetIhp/rNySZDt99GzvEpHEwSi84q3fabqI6aLU1ZfSVM vEuez3KaU/9n/I+j9nJ6G3zp87APksRT9Up2ka8JdVJ2wA58zX48A0POnWtUGR4UFXBi WV9zZf3fa0/tkSTcEHDZF+iK1JNhDLktSUhE5+HgtkySaNdmHIVPKTa/eeXh/LoI8TFl pjhw== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20240605; h=cc:to:subject:message-id:date:mime-version:references:in-reply-to :from:dkim-signature; bh=1YVI0hayK/pE2zwI/10lFSwnfbjn36xvcFyuXZ+58V8=; fh=pYecjgC/DXNXsUX9w2k0A1WyGOuBv8s9DZGTT7qA22o=; b=dg2gI0gMB6hLCOdkmEMORMdVDvcxMG9VS6wIF4E3FFiDOnTpJ8KC5HVTgueegnDGEQ CPXghMQhYNqyQ74/uu+Fyr6HqiCNhTVGxwNuu+Wb77KZI7mNLJ6o/JgNeasgisjcZjEx OsMvtmrtE0xd0/MYfxpBdx0x/SU2WBomtqjrsFJAp6c2Y8Aa+A/I+3jiH+SNcR8XSpog 2GTub+d7boPoXz04RtBs66YYFJs8PBGBPW/k6/jSU/cq5zDAQWT4VPKsu/DaOZh9sIXX 7irhNdpfXoO/yOHhLFnkSO3aBf3uYTg0vtKhPSXdzpt5aYF84XmBz1iYPuQ7Ph/OZ0MH DS+w==; darn=kvack.org ARC-Authentication-Results: i=1; mx.google.com; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1775079827; x=1775684627; darn=kvack.org; h=cc:to:subject:message-id:date:mime-version:references:in-reply-to :from:from:to:cc:subject:date:message-id:reply-to; bh=1YVI0hayK/pE2zwI/10lFSwnfbjn36xvcFyuXZ+58V8=; b=AcdV4d3jGF/Oj47YLzCpb31TUMvTGf6bN4VB+FFjho+u2cwRcSKWV6QRZ89lTMXXQK KtkArkF2ZdDRLZK743eXBaYbhIHCaOmxLaBg4LZa3IFnXr2PZFjb40bxD8ZrN0jBqd1d K/zURlSQAEV2+tHngc+k4OQayN6d+RKOWyMx+mliyojtQYNyyTVic1WIRupGO/2F6gME 997JNBLp3I1M35WjEJdBsGESkVlHjRKydBl/OMPyye8D6EkIV/3c6w+bAbKFxAZXA9tk jhqTrLz2dEoyxmuR6LoSHKNYR7+nKio7hXmiHTSSrzXjNdQlfY1/qJpE8Af9Mv5FPUH5 1qsA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1775079827; x=1775684627; h=cc:to:subject:message-id:date:mime-version:references:in-reply-to :from:x-gm-gg:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=1YVI0hayK/pE2zwI/10lFSwnfbjn36xvcFyuXZ+58V8=; b=AVU+Qs0lWYLIs4URyIN/UKUO79xi0JjfycArR738MYen272hKM9JvxjrsrQYxuadpv sZ+EYoMzK2gnnZ8/Wx77DaU4he04xwRbIw7OtA9loWadtpW1tJl24K3qevhwhYpZV8do 5nfHG7njIcaDTlunWSnrtxayf4XSeRj1toddC05cUfvGnKTRQ/iKKK35EQ9yvd87iujr sIAysAKRJwYTNYJ4TX/9+CbKtpuKz3TkOJmTEO8GNHtekNnXX8MSklxRM7oAfiQXx9pl dfMUeXpwWE/jM83WAHPlsy5vazOHF+CJSu+j/whMipFMvjcMNH4PUw2XZxqID9UKBCR+ Hbhw== X-Forwarded-Encrypted: i=1; AJvYcCUbMJYaI/yVrUP67Jg5y0RTMRMSJbDE+q+xlp4q/DxHM8DKYpwkdpXcrAImQ/eg4Nvxcq2VQBKrpQ==@kvack.org X-Gm-Message-State: AOJu0YxilVSdY7yNcWgt7klD5uVOdNoLMnvugLpw7kyh7puBQTjnxQXt uB76SYgVG8w2DND8ZBRtfXscjhb05KsOJHKpnXhubsiSUDhdcNniXqfWDOdklCMjMwFiIfkQaFi LAydhbzdIfR7b0TwkcaTnbgFT6wZDL9Bhv06ypzRf X-Gm-Gg: ATEYQzyMZLyZQ0Z1NziHPZfviTCKOqPqkBxoPySoPI3Ll2DbKq+BQyH8KUnBo4eujyD heMJxC4k6GPDkkkO1+d3ICOAbpRTGIPVGp+sfVT4V/5EF5LipLQaZK8wr1kOfZSd0n/yMq3Iv51 nFW2BucdvOwiB4AdmnS4NUG7dyp1gJx/pUzJg0AkKus4qVLoNdfRg0GPZaTcu6ptHqG+0vo1xa0 TTeQKIeos/5ouy+aWNOMOhdvQVx9zbl8q6qqV6oMPgWUT/okZng2fdqEBiVycHqvn1GjUa8ywyM /rxeHsxsyktMdmj0nFpA1Yp8LxW2im29s8zzsrmwvMaGT3mOPa8Q5v0EoBBJZPakfci8TzzNBnz 35rM8 X-Received: by 2002:a05:6102:14aa:b0:5f5:4055:4556 with SMTP id ada2fe7eead31-60583dd2d96mr513571137.4.1775079826765; Wed, 01 Apr 2026 14:43:46 -0700 (PDT) Received: from 176938342045 named unknown by gmailapi.google.com with HTTPREST; Wed, 1 Apr 2026 14:43:45 -0700 Received: from 176938342045 named unknown by gmailapi.google.com with HTTPREST; Wed, 1 Apr 2026 14:43:45 -0700 From: Ackerley Tng In-Reply-To: References: <20260326-gmem-inplace-conversion-v4-0-e202fe950ffd@google.com> <20260326-gmem-inplace-conversion-v4-7-e202fe950ffd@google.com> MIME-Version: 1.0 Date: Wed, 1 Apr 2026 14:43:45 -0700 X-Gm-Features: AQROBzB6Nm5vUeDCJFrJRBVH_sKZ67O9qJoiuhUvd8m5ueyFjs7DkYFcGmC74e4 Message-ID: Subject: Re: [PATCH RFC v4 07/44] KVM: guest_memfd: Only prepare folios for private pages To: Michael Roth Cc: aik@amd.com, andrew.jones@linux.dev, binbin.wu@linux.intel.com, brauner@kernel.org, chao.p.peng@linux.intel.com, david@kernel.org, ira.weiny@intel.com, jmattson@google.com, jroedel@suse.de, jthoughton@google.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, 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 , Baoquan He , Barry Song , Axel Rasmussen , Yuanchu Xie , Wei Xu , Jason Gunthorpe , 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 Content-Type: text/plain; charset="UTF-8" X-Rspamd-Queue-Id: 4EF1540017 X-Stat-Signature: gmja9bdwrpgdnmzp7yzg8fph9agcnuf8 X-Rspam-User: X-Rspamd-Server: rspam07 X-HE-Tag: 1775079828-636122 X-HE-Meta: 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 uOUzhNeW jsH5YxlPQZ2FEz3VGs4x8gmjloPMRO6MtiYqqL7CfDNk0W/rISjblrCKYCDAePTeJLeyfZDlp61IsYxxkZfdvopbR56FMbKy+ny3oFoyi0FC/cK0XUpAgcAWrMd5+SyC0WrsjAI6ZLJp3G9hx3GPyEgDmCOVhDKksflps3U/IUx96cbSjq2tNJrLEqTxtGoCIC50cJdYUB1s8lBeKb2NzA1HIjzaBD44BqAbGrbdaZAlq9VcQPAn9G1NgFB6bVCeixWzkO/fePMq6tl6pt8varDpnQat8NgjN7OPAVT4IAV7Y2/aOSWDiqyU0DpY4fHvb0LJhMtQh60StmEHvIGLw9MiXkFH4shN9zmcPNw0kWSidETp5xFit8liqbkEuWRp47lrJqtyMuUVou4w= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Michael Roth writes: > On Wed, Apr 01, 2026 at 07:05:16AM -0700, Ackerley Tng wrote: >> Ackerley Tng writes: >> >> > All-shared guest_memfd used to be only supported for non-CoCo VMs where >> > preparation doesn't apply. INIT_SHARED is about to be supported for >> > non-CoCo VMs in a later patch in this series. >> > >> > In addition, KVM_SET_MEMORY_ATTRIBUTES2 is about to be supported in >> > guest_memfd in a later patch in this series. >> > >> > This means that the kvm fault handler may now call kvm_gmem_get_pfn() on a >> > shared folio for a CoCo VM where preparation applies. >> > >> > Add a check to make sure that preparation is only performed for private >> > folios. >> > >> > Preparation will be undone on freeing (see kvm_gmem_free_folio()) and on >> > conversion to shared. >> > >> > Signed-off-by: Ackerley Tng >> > --- >> > virt/kvm/guest_memfd.c | 9 ++++++--- >> > 1 file changed, 6 insertions(+), 3 deletions(-) >> > >> > diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c >> > index b6ffa8734175d..d414ebfcb4c19 100644 >> > --- a/virt/kvm/guest_memfd.c >> > +++ b/virt/kvm/guest_memfd.c >> > @@ -900,6 +900,7 @@ int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot, >> > int *max_order) >> > { >> > pgoff_t index = kvm_gmem_get_index(slot, gfn); >> > + struct inode *inode; >> > struct folio *folio; >> > int r = 0; >> > >> > @@ -907,7 +908,8 @@ int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot, >> > if (!file) >> > return -EFAULT; >> > >> > - filemap_invalidate_lock_shared(file_inode(file)->i_mapping); >> > + inode = file_inode(file); >> > + filemap_invalidate_lock_shared(inode->i_mapping); >> > >> > folio = __kvm_gmem_get_pfn(file, slot, index, pfn, max_order); >> > if (IS_ERR(folio)) { >> > @@ -920,7 +922,8 @@ int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot, >> > folio_mark_uptodate(folio); >> > } >> > >> > - r = kvm_gmem_prepare_folio(kvm, slot, gfn, folio); >> > + if (kvm_gmem_is_private_mem(inode, index)) >> > + r = kvm_gmem_prepare_folio(kvm, slot, gfn, folio); >> >> Michael, I might have misunderstood you at the last guest_memfd call: >> sev_gmem_prepare() doesn't prepare a page for being a shared page, >> right? Does this work? That prepare is only called to "make private"? > > Hmm, I guess your guest_memfd-inplace-conversion-v4 branch is out of sync with > these patches? > My bad, it was. I just force-pushed to github to synchronize them with this patch series. > I have the below local patch based on top of that for SNP-specific enablement, > which is basically identically, so suffice to say: yes, this should work > for SNP :) If any architecture pops up that needs to do some prep in > advance of mapping shared pages, then we could potentially plumb the > shared/private flag through to the arch-specific prep hook, as was also > suggested on the call, but it doesn't seem like that's needed by any > users for now. > Thanks for checking :) > -Mike > > Author: Michael Roth > Date: Mon Oct 27 07:58:32 2025 -0500 > > KVM: guest_memfd: Don't prepare shared folios > > In the current guest_memfd logic, "preparation" is only used currently > to describe the additional work of putting a guest_memfd page into an > architecturally-defined "private" state, such as updating RMP table > entries for SEV-SNP guests. As such, there's no input to the > corresponding kvm_arch_gmem_prepare() hooks as to whether a page is > being prepared/accessed as shared or as private, so "preparation" will > end up being erroneously done on pages that were supposed to remain in a > shared state. Rather than plumb through the additional information > needed to distinguish between shared vs. private preparation, just > continue to only do preparation on private pages, as was the case prior > to support for GUEST_MEMFD_FLAG_MMAP being introduced. > > Signed-off-by: Michael Roth > > diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c > index 3acc6d983449..4869e59e4fc5 100644 > --- a/virt/kvm/guest_memfd.c > +++ b/virt/kvm/guest_memfd.c > @@ -1249,7 +1249,8 @@ int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot, > folio_mark_uptodate(folio); > } > > - r = kvm_gmem_prepare_folio(kvm, slot, gfn, folio); > + if (!kvm_gmem_is_shared_mem(file_inode(file), index)) > + r = kvm_gmem_prepare_folio(kvm, slot, gfn, folio); > > folio_unlock(folio); > >> >> > >> > folio_unlock(folio); >> > >> > @@ -930,7 +933,7 @@ int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot, >> > folio_put(folio); >> > >> > out: >> > - filemap_invalidate_unlock_shared(file_inode(file)->i_mapping); >> > + filemap_invalidate_unlock_shared(inode->i_mapping); >> > return r; >> > } >> > EXPORT_SYMBOL_FOR_KVM_INTERNAL(kvm_gmem_get_pfn); >> > >> > -- >> > 2.53.0.1018.g2bb0e51243-goog