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.gnu.org (lists.gnu.org [209.51.188.17]) (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 87CE4C02198 for ; Wed, 12 Feb 2025 17:33:14 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1tiGbS-0000mo-8M; Wed, 12 Feb 2025 12:32:50 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1tiGbN-0000lp-6C for qemu-devel@nongnu.org; Wed, 12 Feb 2025 12:32:46 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1tiGbJ-0004ZU-6o for qemu-devel@nongnu.org; Wed, 12 Feb 2025 12:32:42 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1739381560; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=pWyecTaypBns+gpe4qOWDjVM7MDUMdV8SfX1LeARB/U=; b=Of0yP94WKrgOmYlGHklt4tYxf4yqrGoG93XPchnD7hcegJ0LqwXg5tk6B0oPMWOnDm4d0O YPMFb+adhAr5bk3wIqQdbwQQ5hHrKjWELOdfBc3lA/RrAmB/q8K0rrllL0NqprsxfOVfqQ NHEzcwjapeJjdxQwz6e5vMUmdKuulwY= Received: from mx-prod-mc-05.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-202-blJ4CU2pPgiF_2D1c_zhTw-1; Wed, 12 Feb 2025 12:32:37 -0500 X-MC-Unique: blJ4CU2pPgiF_2D1c_zhTw-1 X-Mimecast-MFC-AGG-ID: blJ4CU2pPgiF_2D1c_zhTw_1739381556 Received: from mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.93]) (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 mx-prod-mc-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 1D4CE195609D; Wed, 12 Feb 2025 17:32:35 +0000 (UTC) Received: from redhat.com (unknown [10.44.33.168]) by mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 35DCB1800359; Wed, 12 Feb 2025 17:32:31 +0000 (UTC) Date: Wed, 12 Feb 2025 18:32:29 +0100 From: Kevin Wolf To: Paolo Bonzini Cc: qemu-block@nongnu.org, hreitz@redhat.com, manos.pitsidianakis@linaro.org, qemu-devel@nongnu.org, qemu-rust@nongnu.org Subject: Re: [PATCH 08/11] rust/block: Add driver module Message-ID: References: <20250211214328.640374-1-kwolf@redhat.com> <20250211214328.640374-9-kwolf@redhat.com> <7fe0ba58-8d91-49c7-8f93-d17f42c74fbc@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <7fe0ba58-8d91-49c7-8f93-d17f42c74fbc@redhat.com> X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 Received-SPF: pass client-ip=170.10.133.124; envelope-from=kwolf@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -35 X-Spam_score: -3.6 X-Spam_bar: --- X-Spam_report: (-3.6 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1.495, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=0.001, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Am 12.02.2025 um 17:43 hat Paolo Bonzini geschrieben: > On 2/11/25 22:43, Kevin Wolf wrote: > > + /// Reads data from the child node into a linear typed buffer. > > + pub async fn read(&self, offset: u64, buf: &mut T) -> io::Result<()> { > > + unsafe { > > + self.read_raw(offset, buf.buffer_len(), buf.buffer_mut_ptr()) > > + .await > > + } > > + } > > + > > + /// Reads data from the child node into a linear, potentially uninitialised typed buffer. > > + pub async fn read_uninit( > > + &self, > > + offset: u64, > > + mut buf: MaybeUninit, > > I think Rust doesn't guarantee no copies here, so maybe this could be Do you think that in practice the compiler won't optimise the copy away? Or is this more of a theoretical concern? > pub async fn read_uninit( > &self, > offset: u64, > buf: &mut MaybeUninit, > ) -> io::Result<&mut T> > > using assume_init_mut(). Are you sure that callers are ok with only getting a &mut T rather than an owned T? Kevin