From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sean Christopherson Date: Tue, 31 Oct 2023 07:10:08 -0700 Subject: [PATCH v13 16/35] KVM: Add KVM_CREATE_GUEST_MEMFD ioctl() for guest-specific backing memory In-Reply-To: References: <20231027182217.3615211-1-seanjc@google.com> <20231027182217.3615211-17-seanjc@google.com> Message-ID: List-Id: To: kvm-riscv@lists.infradead.org MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit On Tue, Oct 31, 2023, Chao Gao wrote: > >+int kvm_gmem_create(struct kvm *kvm, struct kvm_create_guest_memfd *args) > >+{ > >+ loff_t size = args->size; > >+ u64 flags = args->flags; > >+ u64 valid_flags = 0; > >+ > >+ if (flags & ~valid_flags) > >+ return -EINVAL; > >+ > >+ if (size < 0 || !PAGE_ALIGNED(size)) > >+ return -EINVAL; > > is size == 0 a valid case? Nope, this is a bug. > >+ if (!xa_empty(&gmem->bindings) && > >+ xa_find(&gmem->bindings, &start, end - 1, XA_PRESENT)) { > >+ filemap_invalidate_unlock(inode->i_mapping); > >+ goto err; > >+ } > >+ > >+ /* > >+ * No synchronize_rcu() needed, any in-flight readers are guaranteed to > >+ * be see either a NULL file or this new file, no need for them to go > >+ * away. > >+ */ > >+ rcu_assign_pointer(slot->gmem.file, file); > >+ slot->gmem.pgoff = start; > >+ > >+ xa_store_range(&gmem->bindings, start, end - 1, slot, GFP_KERNEL); > >+ filemap_invalidate_unlock(inode->i_mapping); > >+ > >+ /* > >+ * Drop the reference to the file, even on success. The file pins KVM, > >+ * not the other way 'round. Active bindings are invalidated if the > >+ * file is closed before memslots are destroyed. > >+ */ > >+ fput(file); > >+ return 0; > >+ > >+err: > >+ fput(file); > >+ return -EINVAL; > > The cleanup, i.e., filemap_invalidate_unlock() and fput(), is common. So, I think it > may be slightly better to consolidate the common part e.g., I would prefer to keep this as-is. Only goto needs the unlock, and I find it easier to understand the success vs. error paths with explicit returns. But it's not a super strong preference. From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-yw1-f201.google.com (mail-yw1-f201.google.com [209.85.128.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4BDD01DDE0 for ; Tue, 31 Oct 2023 14:10:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="KHAqLBeV" Received: by mail-yw1-f201.google.com with SMTP id 00721157ae682-5afacc566f3so49349337b3.3 for ; Tue, 31 Oct 2023 07:10:10 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1698761410; x=1699366210; darn=lists.linux.dev; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=qnQOjymnTrZBwkJL50GP/1+n+ilT5bo3LZ+viwIL69A=; b=KHAqLBeVAASN8oL2ZWoSCs/Bu1P2JCtoGB3aXkT+eSrZPVgShMjIfyX0ce7OjlFDbx 9fEgZEdHs2hmp7xrdftDY0bPqfQrEd10Y2GVCP+VVivBw0KU2NKssUhzZzHIh6/ElKJi B1NvYsHgy9YrUQt3SzB7MPTVs++Qhkbp/uIaqBIvTlBhRT3ff64JHWez4NvNeLwPvjLk jCI5ODS2iZYONtxP03M1iQL1Fd6I/vgsjqTAiDNPHInWKelwI+vMBfbdXxTtas0JTgot 25r2MWN/Ol80SLgD6/FbBxJT+4z1Isw+G1/eJTM6BVJbk89EUGdgrVQ+zjy3tDksiHZ2 2CqA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1698761410; x=1699366210; 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=qnQOjymnTrZBwkJL50GP/1+n+ilT5bo3LZ+viwIL69A=; b=WcqiyVYkqpo32aLhkcjB3y5GP8uIiy9RjHBd+l+R18PTfhvaWZbJBUW6ynsn+fZypn LZXO5RXpIbnqtYaOduD8vSZiD1TUe6LIypiNNdtNr00fN1QWMeKG7F4ZGes6nI0AMn7+ qRxQQbVLzh/4qA2gWzvI+WLjUdidc+2/U5NR9hMxNm2+LnWC8+zXAyywoUcU6ZXxj/MZ 4HH1KkwxH+TOKBNuyK40qLrGT0n3x4Bk1ri4fAb2U/pKvZklzsx88sD5JcBrrd+o55fN pz5Rfw8OfemHCSjZOd6fpU8C1EjWRGzXPEchzfVUfbb4sYreWe0J6vZF6yDZKIScIYrf V1BQ== X-Gm-Message-State: AOJu0YzsOBR3bmZkb+pQ5udad0yGF/SUsiPAEgt0YLDddT1Rj7x9TSZ7 u5tnBHmGLHCSZ8UdZ9U68tD58deb66I= X-Google-Smtp-Source: AGHT+IHZDXQi7UJsz3IrNX3ZHQxUCVwQKR+0lKBMLeJ46WZVaPkGJ08yzTLT3JODvkoGCJ0IGZA0c9r9iJw= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5c37]) (user=seanjc job=sendgmr) by 2002:a81:a14c:0:b0:59b:eea4:a5a6 with SMTP id y73-20020a81a14c000000b0059beea4a5a6mr274540ywg.0.1698761410163; Tue, 31 Oct 2023 07:10:10 -0700 (PDT) Date: Tue, 31 Oct 2023 07:10:08 -0700 In-Reply-To: Precedence: bulk X-Mailing-List: kvmarm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20231027182217.3615211-1-seanjc@google.com> <20231027182217.3615211-17-seanjc@google.com> Message-ID: Subject: Re: [PATCH v13 16/35] KVM: Add KVM_CREATE_GUEST_MEMFD ioctl() for guest-specific backing memory From: Sean Christopherson To: Chao Gao Cc: Paolo Bonzini , Marc Zyngier , Oliver Upton , Huacai Chen , Michael Ellerman , Anup Patel , Paul Walmsley , Palmer Dabbelt , Albert Ou , Alexander Viro , Christian Brauner , "Matthew Wilcox (Oracle)" , Andrew Morton , kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Xiaoyao Li , Xu Yilun , Chao Peng , Fuad Tabba , Jarkko Sakkinen , Anish Moorthy , David Matlack , Yu Zhang , Isaku Yamahata , "=?utf-8?Q?Micka=C3=ABl_Sala=C3=BCn?=" , Vlastimil Babka , Vishal Annapurve , Ackerley Tng , Maciej Szmigiero , David Hildenbrand , Quentin Perret , Michael Roth , Wang , Liam Merwick , Isaku Yamahata , "Kirill A . Shutemov" Content-Type: text/plain; charset="us-ascii" On Tue, Oct 31, 2023, Chao Gao wrote: > >+int kvm_gmem_create(struct kvm *kvm, struct kvm_create_guest_memfd *args) > >+{ > >+ loff_t size = args->size; > >+ u64 flags = args->flags; > >+ u64 valid_flags = 0; > >+ > >+ if (flags & ~valid_flags) > >+ return -EINVAL; > >+ > >+ if (size < 0 || !PAGE_ALIGNED(size)) > >+ return -EINVAL; > > is size == 0 a valid case? Nope, this is a bug. > >+ if (!xa_empty(&gmem->bindings) && > >+ xa_find(&gmem->bindings, &start, end - 1, XA_PRESENT)) { > >+ filemap_invalidate_unlock(inode->i_mapping); > >+ goto err; > >+ } > >+ > >+ /* > >+ * No synchronize_rcu() needed, any in-flight readers are guaranteed to > >+ * be see either a NULL file or this new file, no need for them to go > >+ * away. > >+ */ > >+ rcu_assign_pointer(slot->gmem.file, file); > >+ slot->gmem.pgoff = start; > >+ > >+ xa_store_range(&gmem->bindings, start, end - 1, slot, GFP_KERNEL); > >+ filemap_invalidate_unlock(inode->i_mapping); > >+ > >+ /* > >+ * Drop the reference to the file, even on success. The file pins KVM, > >+ * not the other way 'round. Active bindings are invalidated if the > >+ * file is closed before memslots are destroyed. > >+ */ > >+ fput(file); > >+ return 0; > >+ > >+err: > >+ fput(file); > >+ return -EINVAL; > > The cleanup, i.e., filemap_invalidate_unlock() and fput(), is common. So, I think it > may be slightly better to consolidate the common part e.g., I would prefer to keep this as-is. Only goto needs the unlock, and I find it easier to understand the success vs. error paths with explicit returns. But it's not a super strong preference. 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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id F080DC4332F for ; Tue, 31 Oct 2023 14:10:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:Cc:To:From:Subject:Message-ID: References:Mime-Version:In-Reply-To:Date:Reply-To:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Owner; bh=RgttpHn374erxByzdeuqKbu7ZcP0fBH+arALnqJuqN0=; b=mpGgN1L1nxPBqPwhU3L1Zwigcy e1rMLbN8Ki1Kc9Q7qXWHvVXwcjkPeC1r9uzYQMgHM9selbTu1owSEBktu9uVmrC6OR2ZLCJpN2n9z /+XvQgfDQzxaT6EfwewA6jSVJz2E2DmzJK6bHe3lk8KeRQGkVJ/Ww1Ii5YWp1kNUb5dmlBipRGJUh lAUBaUjRWImte8oDb7BX8K0VKlspSBjiySkfdst8yVT6mEi1Yi4DMAT9ZlGEcq9/WT60Saf346aCf nDfqfnpb+unoULI97+JvVqOhfwsD3gJKVCaDoEEWKfZJDYjU1dZ1asw+XVgem8nsRQDEjLe7ZQboe sfFL5NWA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1qxpRf-005Op4-1a; Tue, 31 Oct 2023 14:10:15 +0000 Received: from mail-yw1-x1149.google.com ([2607:f8b0:4864:20::1149]) by bombadil.infradead.org with esmtps (Exim 4.96 #2 (Red Hat Linux)) id 1qxpRb-005On9-2n for linux-riscv@lists.infradead.org; Tue, 31 Oct 2023 14:10:13 +0000 Received: by mail-yw1-x1149.google.com with SMTP id 00721157ae682-5a7af53bde4so60423187b3.0 for ; Tue, 31 Oct 2023 07:10:10 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1698761410; x=1699366210; darn=lists.infradead.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=qnQOjymnTrZBwkJL50GP/1+n+ilT5bo3LZ+viwIL69A=; b=dNCfNET6nZ5ncGz+msMYMug45u2Jfk8KiZiZluqYItKzSkSjjsw/m/z7FFiMnlme8n a3vI1ykM4G/zQyYmQbtJKBRBiPXaAqadn8nZa0N1EsDZq6aArn6kxEwz/8e53DlmUDpw menFAFyD6AqbxJRUntezvSUMSUyrgfZgsIYSTviBhN/8nl/+juH6zNpe0Rb6QymNzUnt fYfSMop+VgdDDpADO+jblKqSy03DBl6eZSCEvmFEZb4JbVSuTuDLKgdICvY8y1m9Up8d glccQ8nmPdluv494XIQuIftxSTOzB+cEO+C/Tyfd1ZjdGHiqOQkB0/XSR4YGfQPCExBn i7sg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1698761410; x=1699366210; 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=qnQOjymnTrZBwkJL50GP/1+n+ilT5bo3LZ+viwIL69A=; b=iqn9KPeSHvuH77VdxJeHQw+SFr5yVmvS2isXbYUSTBBv27sjU+acIfM0UFcpfdr/cC p+/Gd/zAGer9Jk6Y9WNIkImlJZ/qNNsuNE/alre9mp0VJdPMDHOUtNqNV0jkd8gELri8 7uL/2eMbBSk+ZNc/W7PNwnRRXZqUzmV9PrfZI1tkXOrADpmSXkWjfsmU2Sr13ChiOwyP 8inkAX3Kn90M127OjzvpleWNNjdGP+pXJc99tNLIqInBsJMebbtgP7Bs27uWKMMwTb2F e3SyliRIMXxz3Efb2lGgdUsneuprJB++mpFvGLEnY0mEvAPSEt6e86t9IG/hPWkzi7G3 kE6Q== X-Gm-Message-State: AOJu0Yxl+NgmkKkF6iXDJoj24WaSgY1+B10zfd4l651a8zKHCcFcIKaW CAapozJDaCQ9x+8D26YN8D1NkiJDvS4= X-Google-Smtp-Source: AGHT+IHZDXQi7UJsz3IrNX3ZHQxUCVwQKR+0lKBMLeJ46WZVaPkGJ08yzTLT3JODvkoGCJ0IGZA0c9r9iJw= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5c37]) (user=seanjc job=sendgmr) by 2002:a81:a14c:0:b0:59b:eea4:a5a6 with SMTP id y73-20020a81a14c000000b0059beea4a5a6mr274540ywg.0.1698761410163; Tue, 31 Oct 2023 07:10:10 -0700 (PDT) Date: Tue, 31 Oct 2023 07:10:08 -0700 In-Reply-To: Mime-Version: 1.0 References: <20231027182217.3615211-1-seanjc@google.com> <20231027182217.3615211-17-seanjc@google.com> Message-ID: Subject: Re: [PATCH v13 16/35] KVM: Add KVM_CREATE_GUEST_MEMFD ioctl() for guest-specific backing memory From: Sean Christopherson To: Chao Gao Cc: Paolo Bonzini , Marc Zyngier , Oliver Upton , Huacai Chen , Michael Ellerman , Anup Patel , Paul Walmsley , Palmer Dabbelt , Albert Ou , Alexander Viro , Christian Brauner , "Matthew Wilcox (Oracle)" , Andrew Morton , kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Xiaoyao Li , Xu Yilun , Chao Peng , Fuad Tabba , Jarkko Sakkinen , Anish Moorthy , David Matlack , Yu Zhang , Isaku Yamahata , "=?utf-8?Q?Micka=C3=ABl_Sala=C3=BCn?=" , Vlastimil Babka , Vishal Annapurve , Ackerley Tng , Maciej Szmigiero , David Hildenbrand , Quentin Perret , Michael Roth , Wang , Liam Merwick , Isaku Yamahata , "Kirill A . Shutemov" X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20231031_071011_909600_BC9D0B96 X-CRM114-Status: GOOD ( 14.97 ) X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org On Tue, Oct 31, 2023, Chao Gao wrote: > >+int kvm_gmem_create(struct kvm *kvm, struct kvm_create_guest_memfd *args) > >+{ > >+ loff_t size = args->size; > >+ u64 flags = args->flags; > >+ u64 valid_flags = 0; > >+ > >+ if (flags & ~valid_flags) > >+ return -EINVAL; > >+ > >+ if (size < 0 || !PAGE_ALIGNED(size)) > >+ return -EINVAL; > > is size == 0 a valid case? Nope, this is a bug. > >+ if (!xa_empty(&gmem->bindings) && > >+ xa_find(&gmem->bindings, &start, end - 1, XA_PRESENT)) { > >+ filemap_invalidate_unlock(inode->i_mapping); > >+ goto err; > >+ } > >+ > >+ /* > >+ * No synchronize_rcu() needed, any in-flight readers are guaranteed to > >+ * be see either a NULL file or this new file, no need for them to go > >+ * away. > >+ */ > >+ rcu_assign_pointer(slot->gmem.file, file); > >+ slot->gmem.pgoff = start; > >+ > >+ xa_store_range(&gmem->bindings, start, end - 1, slot, GFP_KERNEL); > >+ filemap_invalidate_unlock(inode->i_mapping); > >+ > >+ /* > >+ * Drop the reference to the file, even on success. The file pins KVM, > >+ * not the other way 'round. Active bindings are invalidated if the > >+ * file is closed before memslots are destroyed. > >+ */ > >+ fput(file); > >+ return 0; > >+ > >+err: > >+ fput(file); > >+ return -EINVAL; > > The cleanup, i.e., filemap_invalidate_unlock() and fput(), is common. So, I think it > may be slightly better to consolidate the common part e.g., I would prefer to keep this as-is. Only goto needs the unlock, and I find it easier to understand the success vs. error paths with explicit returns. But it's not a super strong preference. _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv 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 lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id DCEEDC4332F for ; Tue, 31 Oct 2023 14:11:03 +0000 (UTC) Authentication-Results: lists.ozlabs.org; dkim=fail reason="signature verification failed" (2048-bit key; unprotected) header.d=google.com header.i=@google.com header.a=rsa-sha256 header.s=20230601 header.b=szmtZSAN; dkim-atps=neutral Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4SKX9f2jVMz2xTN for ; Wed, 1 Nov 2023 01:11:02 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; 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Tue, 31 Oct 2023 07:10:10 -0700 (PDT) Date: Tue, 31 Oct 2023 07:10:08 -0700 In-Reply-To: Mime-Version: 1.0 References: <20231027182217.3615211-1-seanjc@google.com> <20231027182217.3615211-17-seanjc@google.com> Message-ID: Subject: Re: [PATCH v13 16/35] KVM: Add KVM_CREATE_GUEST_MEMFD ioctl() for guest-specific backing memory From: Sean Christopherson To: Chao Gao Content-Type: text/plain; charset="us-ascii" X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: kvm@vger.kernel.org, David Hildenbrand , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Chao Peng , linux-riscv@lists.infradead.org, Isaku Yamahata , Marc Zyngier , Huacai Chen , Xiaoyao Li , "Matthew Wilcox \(Oracle\)" , Wang , Fuad Tabba , Yu Zhang , Maciej Szmigiero , Albert Ou , Vlastimil Babka , Michael Roth , Ackerley Tng , Alexander Viro , Paul Walmsley , kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org, =?utf-8?Q?Micka=C3=ABl_Sala=C3=BCn?= , Isaku Yamahata , Christian Brauner , Quentin Perret , L iam Merwick , linux-mips@vger.kernel.org, Oliver Upton , David Matlack , Jarkko Sakkinen , Palmer Dabbelt , "Kirill A . Shutemov" , kvm-riscv@lists.infradead.org, Anup Patel , linux-fsdevel@vger.kernel.org, Paolo Bonzini , Andrew Morton , Vishal Annapurve , linuxppc-dev@lists.ozlabs.org, Xu Yilun , Anish Moorthy Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Tue, Oct 31, 2023, Chao Gao wrote: > >+int kvm_gmem_create(struct kvm *kvm, struct kvm_create_guest_memfd *args) > >+{ > >+ loff_t size = args->size; > >+ u64 flags = args->flags; > >+ u64 valid_flags = 0; > >+ > >+ if (flags & ~valid_flags) > >+ return -EINVAL; > >+ > >+ if (size < 0 || !PAGE_ALIGNED(size)) > >+ return -EINVAL; > > is size == 0 a valid case? Nope, this is a bug. > >+ if (!xa_empty(&gmem->bindings) && > >+ xa_find(&gmem->bindings, &start, end - 1, XA_PRESENT)) { > >+ filemap_invalidate_unlock(inode->i_mapping); > >+ goto err; > >+ } > >+ > >+ /* > >+ * No synchronize_rcu() needed, any in-flight readers are guaranteed to > >+ * be see either a NULL file or this new file, no need for them to go > >+ * away. > >+ */ > >+ rcu_assign_pointer(slot->gmem.file, file); > >+ slot->gmem.pgoff = start; > >+ > >+ xa_store_range(&gmem->bindings, start, end - 1, slot, GFP_KERNEL); > >+ filemap_invalidate_unlock(inode->i_mapping); > >+ > >+ /* > >+ * Drop the reference to the file, even on success. The file pins KVM, > >+ * not the other way 'round. Active bindings are invalidated if the > >+ * file is closed before memslots are destroyed. > >+ */ > >+ fput(file); > >+ return 0; > >+ > >+err: > >+ fput(file); > >+ return -EINVAL; > > The cleanup, i.e., filemap_invalidate_unlock() and fput(), is common. So, I think it > may be slightly better to consolidate the common part e.g., I would prefer to keep this as-is. Only goto needs the unlock, and I find it easier to understand the success vs. error paths with explicit returns. But it's not a super strong preference. 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Shutemov" X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20231031_071011_968850_CEBC7223 X-CRM114-Status: GOOD ( 16.38 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, Oct 31, 2023, Chao Gao wrote: > >+int kvm_gmem_create(struct kvm *kvm, struct kvm_create_guest_memfd *args) > >+{ > >+ loff_t size = args->size; > >+ u64 flags = args->flags; > >+ u64 valid_flags = 0; > >+ > >+ if (flags & ~valid_flags) > >+ return -EINVAL; > >+ > >+ if (size < 0 || !PAGE_ALIGNED(size)) > >+ return -EINVAL; > > is size == 0 a valid case? Nope, this is a bug. > >+ if (!xa_empty(&gmem->bindings) && > >+ xa_find(&gmem->bindings, &start, end - 1, XA_PRESENT)) { > >+ filemap_invalidate_unlock(inode->i_mapping); > >+ goto err; > >+ } > >+ > >+ /* > >+ * No synchronize_rcu() needed, any in-flight readers are guaranteed to > >+ * be see either a NULL file or this new file, no need for them to go > >+ * away. > >+ */ > >+ rcu_assign_pointer(slot->gmem.file, file); > >+ slot->gmem.pgoff = start; > >+ > >+ xa_store_range(&gmem->bindings, start, end - 1, slot, GFP_KERNEL); > >+ filemap_invalidate_unlock(inode->i_mapping); > >+ > >+ /* > >+ * Drop the reference to the file, even on success. The file pins KVM, > >+ * not the other way 'round. Active bindings are invalidated if the > >+ * file is closed before memslots are destroyed. > >+ */ > >+ fput(file); > >+ return 0; > >+ > >+err: > >+ fput(file); > >+ return -EINVAL; > > The cleanup, i.e., filemap_invalidate_unlock() and fput(), is common. So, I think it > may be slightly better to consolidate the common part e.g., I would prefer to keep this as-is. Only goto needs the unlock, and I find it easier to understand the success vs. error paths with explicit returns. But it's not a super strong preference. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel