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; dkim=pass (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 Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=flex--seanjc.bounces.google.com (client-ip=2607:f8b0:4864:20::1149; helo=mail-yw1-x1149.google.com; envelope-from=3wgpbzqykda05rn0wpt11tyr.p1zyv07a22p-qr8yv565.1cyno5.14t@flex--seanjc.bounces.google.com; receiver=lists.ozlabs.org) Received: from mail-yw1-x1149.google.com (mail-yw1-x1149.google.com [IPv6:2607:f8b0:4864:20::1149]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4SKX8k1ZRCz2xPZ for ; Wed, 1 Nov 2023 01:10:12 +1100 (AEDT) Received: by mail-yw1-x1149.google.com with SMTP id 00721157ae682-5b0e9c78309so36495267b3.1 for ; Tue, 31 Oct 2023 07:10:12 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1698761410; x=1699366210; darn=lists.ozlabs.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=szmtZSANeLgEQgNVSNmjd6Qc2fLRkHpYWwSJ7ThX/aIQKaH1C1I4jk89krwFNFEBVK fIXO9O1soLLzlyuP1LUIrjrCG+1+3wKoT8zRyPEzZ/pOuQJi3VY/4Z7xiwhPyiPkpsml N+PyjCBkmpOMBi7OD0lW144hvE7UOuz+VQqW7TpEsjgoSBxnNd8zrYZa9qdd7Y6HORbn 1aDp3z+dJ+pbzkKHnSjcWef8kD0SUVhTvfnWA04FeQ4Sel487RFLYq4c6b6Mm7j+2sjb JqqxxujpR7lB+7l+YBpIzJc8ZVxxHr2lgk0GUvbaod6z45E/JVg+YnEce1QM8/n2AzwX iJxQ== 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=HxM6yiqCuh3deeZEYgaJFCkay8DENmyiPFqBqj2fBi03zr4obq8nCosX0uzkWmg8EG BCwxornHthpPNiIcS8AbEKHpNCZdpz7JB1SwMKWjNSeA4Immstp4pYbVFbrjeKRWzJAB ecyKzfR61v/I2xpivmvO68cWd4SAMgg3ZDgLPu1+p6DjaX/y4q1G0LCk1PtOFkDqnplK 0BL6ZsfxLjydqtgeRzTpw45vAbZJKLFHyijTh20NmnwUk4vFLd5SgJgAc9DnD+wDxhCu uNVFRipf6d22lIugn090saewU+tMGyFLfHa2KcOnu9wKCFwkRcSPnlhixwza03+82qyd w5AQ== X-Gm-Message-State: AOJu0YwsWIH+aP1vizM6b8OpnG7MLq+oIQl/xSOZKn9+LRHD7iBJC+6L doB6syS08fN+sFYH25Z49xtpjZ4HhaM= 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 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.