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]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1192EC54FB3 for ; Thu, 29 May 2025 18:26:24 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 4EB856B0095; Thu, 29 May 2025 14:26:24 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 49C0D6B0096; Thu, 29 May 2025 14:26:24 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 388936B0098; Thu, 29 May 2025 14:26:24 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id 176536B0095 for ; Thu, 29 May 2025 14:26:24 -0400 (EDT) Received: from smtpin21.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay02.hostedemail.com (Postfix) with ESMTP id B1FEB120F56 for ; Thu, 29 May 2025 18:26:23 +0000 (UTC) X-FDA: 83496775446.21.DF76A37 Received: from mail-pf1-f202.google.com (mail-pf1-f202.google.com [209.85.210.202]) by imf13.hostedemail.com (Postfix) with ESMTP id D2B8720009 for ; Thu, 29 May 2025 18:26:21 +0000 (UTC) Authentication-Results: imf13.hostedemail.com; dkim=pass header.d=google.com header.s=20230601 header.b=fzvAmAG3; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf13.hostedemail.com: domain of 3zKY4aAsKCEUhjrlysl50unnvvnsl.jvtspu14-ttr2hjr.vyn@flex--ackerleytng.bounces.google.com designates 209.85.210.202 as permitted sender) smtp.mailfrom=3zKY4aAsKCEUhjrlysl50unnvvnsl.jvtspu14-ttr2hjr.vyn@flex--ackerleytng.bounces.google.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1748543181; 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=lIz4VHixxBnPERxzo7x/dFPIiGKuMB366F2mMctZln0=; b=YNmpwq3eLjUaEE5DmKaolWEfHGxo7ftSSrQym9+3CmNNdtb/0HUj5zNXWToR5aVSZuy66Q HuaAZcbhX+vdM9t8Du//NT7RA+0IZVk8GNPgstgGFZ8HaOxUPRuXOLbtvgr+52VWpRT8UY aANvqYcdDLDqQN1Xwg8gOQutM4HdxhU= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1748543181; a=rsa-sha256; cv=none; b=GekKy7BJ7sg++4fqd/k/Z1qNgFIxUwbme3I6ML/8hABfxINhGhiBRSp+wxOWmzQ3k2YI+T bhEvjlYG/xfzGrQXdrwubxcAAFSFgkeoX6LTTtCyvw7xWZWVtRFwyXC3/nCoA8UtikgOti mTJg13XOrrQ8frG0GlayktO8ZK6wrSc= ARC-Authentication-Results: i=1; imf13.hostedemail.com; dkim=pass header.d=google.com header.s=20230601 header.b=fzvAmAG3; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf13.hostedemail.com: domain of 3zKY4aAsKCEUhjrlysl50unnvvnsl.jvtspu14-ttr2hjr.vyn@flex--ackerleytng.bounces.google.com designates 209.85.210.202 as permitted sender) smtp.mailfrom=3zKY4aAsKCEUhjrlysl50unnvvnsl.jvtspu14-ttr2hjr.vyn@flex--ackerleytng.bounces.google.com Received: by mail-pf1-f202.google.com with SMTP id d2e1a72fcca58-742aa6581caso934759b3a.3 for ; Thu, 29 May 2025 11:26:21 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1748543181; x=1749147981; darn=kvack.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=lIz4VHixxBnPERxzo7x/dFPIiGKuMB366F2mMctZln0=; b=fzvAmAG3a2xm0lnRIKQ9bv5CQZ4fbDHCPErHC4+y9erF0dLgjmPyMiwo0PQilRQi8G oC5NikKoRUhwduX30SNjdfghwHQjWwbxJBSyJQECXBtg5E4ozNZorlh/pFU6AcQpAc/I B0RbjCDMvFakiNXycH2mmKYRSpYsN3JwV2qg8d+heplLau9fBRd9dvTUoKCbdUiZLCWq LQJUr3PgnzBZfZEfx2zhT3gVna0O3UGXfTkG+RcnYd/wupLapT4A1vob+yS0ckACR38Y rmzybQrGZDy1T0UzEpHZeNZdebGAxGGmMhTbF+9if3stICzas6bWYMEhYKR3ZTRstOqt +Ofg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1748543181; x=1749147981; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=lIz4VHixxBnPERxzo7x/dFPIiGKuMB366F2mMctZln0=; b=BIJgawfqnx0GLBeV2uCBmdvNYxR1xEy3n5zhF6T9PyYyksHh6yZ1tFgytyWc29JL5D DLtKqKuh0TfP2XEuyquU0CE6MN+s8wnKlyGHyL1pffcqjKp0gYpvuu+9uYQhi8wSnXtm ZLcWth7p/ntbIgkXEyHJZStawPq8goXghxidU0lPGWW3WRxtGOWZb6p39gLjYYTwznVr EPprjyqQj8hpm6WcR4XOT+ikINR1ykTUWsImxjYMK1lUCi5iPWhY+sn78xYY2zDWHxqu KAPO7TDTbZFjX7xfCF3N09bHpAZnl4i9pl66S0zhHsTO9Zmv5f57mt4yjXVrKgE4awvd TvIQ== X-Forwarded-Encrypted: i=1; AJvYcCVwXrecDd5a+/re7q41zg8XT5jr7OFKjmEb8Bxp1PWZ/euUi7FodTxBL1hxNyMIiE+qeowoqpW+bA==@kvack.org X-Gm-Message-State: AOJu0YzLzQfQr+b5St0HIKYl9sT06CkV6Ie0vrU1Bc0kI+TzX+mgNPmv OBTiIpsVnN0G8uzmvEnlcLN5SONCcFS9B5rvYQtRHSdn9b4hdUTSsYAImiZiUgcGIu0TgQcYBcs 1UPudTG8+8tquStwSP9ofinKL1g== X-Google-Smtp-Source: AGHT+IGjY0JDCBO+9ghg+QzLazgbH2ijeDdvz/kcUyol+8Id7VYmeYH8PDj4sd4Uw3Qudd2dyxDoTCTFkpAd+/2KBw== X-Received: from pfve9.prod.google.com ([2002:a05:6a00:1a89:b0:73c:26eb:39b0]) (user=ackerleytng job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a00:4fc9:b0:742:8d52:62f1 with SMTP id d2e1a72fcca58-747bd97d3abmr694232b3a.8.1748543180604; Thu, 29 May 2025 11:26:20 -0700 (PDT) Date: Thu, 29 May 2025 11:26:19 -0700 In-Reply-To: <9483e9e3-9b29-49c6-adcc-04fe45ac28fd@linux.intel.com> Mime-Version: 1.0 References: <9483e9e3-9b29-49c6-adcc-04fe45ac28fd@linux.intel.com> Message-ID: Subject: Re: [RFC PATCH v2 02/51] KVM: guest_memfd: Introduce and use shareability to guard faulting From: Ackerley Tng To: Binbin Wu Cc: kvm@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, x86@kernel.org, linux-fsdevel@vger.kernel.org, aik@amd.com, ajones@ventanamicro.com, akpm@linux-foundation.org, amoorthy@google.com, anthony.yznaga@oracle.com, anup@brainfault.org, aou@eecs.berkeley.edu, bfoster@redhat.com, brauner@kernel.org, catalin.marinas@arm.com, chao.p.peng@intel.com, chenhuacai@kernel.org, dave.hansen@intel.com, david@redhat.com, dmatlack@google.com, dwmw@amazon.co.uk, erdemaktas@google.com, fan.du@intel.com, fvdl@google.com, graf@amazon.com, haibo1.xu@intel.com, hch@infradead.org, hughd@google.com, ira.weiny@intel.com, isaku.yamahata@intel.com, jack@suse.cz, james.morse@arm.com, jarkko@kernel.org, jgg@ziepe.ca, jgowans@amazon.com, jhubbard@nvidia.com, jroedel@suse.de, jthoughton@google.com, jun.miao@intel.com, kai.huang@intel.com, keirf@google.com, kent.overstreet@linux.dev, kirill.shutemov@intel.com, liam.merwick@oracle.com, maciej.wieczor-retman@intel.com, mail@maciej.szmigiero.name, maz@kernel.org, mic@digikod.net, michael.roth@amd.com, mpe@ellerman.id.au, muchun.song@linux.dev, nikunj@amd.com, nsaenz@amazon.es, oliver.upton@linux.dev, palmer@dabbelt.com, pankaj.gupta@amd.com, paul.walmsley@sifive.com, pbonzini@redhat.com, pdurrant@amazon.co.uk, peterx@redhat.com, pgonda@google.com, pvorel@suse.cz, qperret@google.com, quic_cvanscha@quicinc.com, quic_eberman@quicinc.com, quic_mnalajal@quicinc.com, quic_pderrin@quicinc.com, quic_pheragu@quicinc.com, quic_svaddagi@quicinc.com, quic_tsoni@quicinc.com, richard.weiyang@gmail.com, rick.p.edgecombe@intel.com, rientjes@google.com, roypat@amazon.co.uk, rppt@kernel.org, seanjc@google.com, shuah@kernel.org, steven.price@arm.com, steven.sistare@oracle.com, suzuki.poulose@arm.com, tabba@google.com, thomas.lendacky@amd.com, usama.arif@bytedance.com, vannapurve@google.com, vbabka@suse.cz, viro@zeniv.linux.org.uk, vkuznets@redhat.com, wei.w.wang@intel.com, will@kernel.org, willy@infradead.org, xiaoyao.li@intel.com, yan.y.zhao@intel.com, yilun.xu@intel.com, yuzenghui@huawei.com, zhiquan1.li@intel.com Content-Type: text/plain; charset="UTF-8" X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: D2B8720009 X-Stat-Signature: 3std1at96tuau8jdykpwtzikg5cx6uhg X-Rspam-User: X-HE-Tag: 1748543181-753363 X-HE-Meta: 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 Ac3jueKX 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Binbin Wu writes: > On 5/15/2025 7:41 AM, Ackerley Tng wrote: >> Track guest_memfd memory's shareability status within the inode as >> opposed to the file, since it is property of the guest_memfd's memory >> contents. >> >> Shareability is a property of the memory and is indexed using the >> page's index in the inode. Because shareability is the memory's >> property, it is stored within guest_memfd instead of within KVM, like >> in kvm->mem_attr_array. >> >> KVM_MEMORY_ATTRIBUTE_PRIVATE in kvm->mem_attr_array must still be >> retained to allow VMs to only use guest_memfd for private memory and >> some other memory for shared memory. >> >> Not all use cases require guest_memfd() to be shared with the host >> when first created. Add a new flag, GUEST_MEMFD_FLAG_INIT_PRIVATE, >> which when set on KVM_CREATE_GUEST_MEMFD, initializes the memory as >> private to the guest, and therefore not mappable by the >> host. Otherwise, memory is shared until explicitly converted to >> private. >> >> Signed-off-by: Ackerley Tng >> Co-developed-by: Vishal Annapurve >> Signed-off-by: Vishal Annapurve >> Co-developed-by: Fuad Tabba >> Signed-off-by: Fuad Tabba >> Change-Id: If03609cbab3ad1564685c85bdba6dcbb6b240c0f >> --- >> Documentation/virt/kvm/api.rst | 5 ++ >> include/uapi/linux/kvm.h | 2 + >> virt/kvm/guest_memfd.c | 124 ++++++++++++++++++++++++++++++++- >> 3 files changed, 129 insertions(+), 2 deletions(-) >> >> diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst >> index 86f74ce7f12a..f609337ae1c2 100644 >> --- a/Documentation/virt/kvm/api.rst >> +++ b/Documentation/virt/kvm/api.rst >> @@ -6408,6 +6408,11 @@ belonging to the slot via its userspace_addr. >> The use of GUEST_MEMFD_FLAG_SUPPORT_SHARED will not be allowed for CoCo VMs. >> This is validated when the guest_memfd instance is bound to the VM. >> >> +If the capability KVM_CAP_GMEM_CONVERSIONS is supported, then the 'flags' field >> +supports GUEST_MEMFD_FLAG_INIT_PRIVATE. > > It seems that the sentence is stale? > Didn't find the definition of KVM_CAP_GMEM_CONVERSIONS. > Thanks. This should read If the capability KVM_CAP_GMEM_SHARED_MEM is supported, and GUEST_MEMFD_FLAG_SUPPORT_SHARED is specified, then the 'flags' field supports GUEST_MEMFD_FLAG_INIT_PRIVATE. >> Setting GUEST_MEMFD_FLAG_INIT_PRIVATE >> +will initialize the memory for the guest_memfd as guest-only and not faultable >> +by the host. >> + > [...] >> >> static int kvm_gmem_init_fs_context(struct fs_context *fc) >> @@ -549,12 +645,26 @@ static const struct inode_operations kvm_gmem_iops = { >> static struct inode *kvm_gmem_inode_make_secure_inode(const char *name, >> loff_t size, u64 flags) >> { >> + struct kvm_gmem_inode_private *private; >> struct inode *inode; >> + int err; >> >> inode = alloc_anon_secure_inode(kvm_gmem_mnt->mnt_sb, name); >> if (IS_ERR(inode)) >> return inode; >> >> + err = -ENOMEM; >> + private = kzalloc(sizeof(*private), GFP_KERNEL); >> + if (!private) >> + goto out; >> + >> + mt_init(&private->shareability); > > shareability is defined only when CONFIG_KVM_GMEM_SHARED_MEM enabled, should be done within CONFIG_KVM_GMEM_SHARED_MEM . > > Yes, thank you! Will also update this to only initialize shareability if (flags & GUEST_MEMFD_FLAG_SUPPORT_SHARED). >> + inode->i_mapping->i_private_data = private; >> + >> + err = kvm_gmem_shareability_setup(private, size, flags); >> + if (err) >> + goto out; >> + >> inode->i_private = (void *)(unsigned long)flags; >> inode->i_op = &kvm_gmem_iops; >> inode->i_mapping->a_ops = &kvm_gmem_aops; >> @@ -566,6 +676,11 @@ static struct inode *kvm_gmem_inode_make_secure_inode(const char *name, >> WARN_ON_ONCE(!mapping_unevictable(inode->i_mapping)); >> >> return inode; >> + >> +out: >> + iput(inode); >> + >> + return ERR_PTR(err); >> } >> >> > [...]