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 8DAF1C87FCF for ; Thu, 7 Aug 2025 13:51:34 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1uk11F-0004gD-15; Thu, 07 Aug 2025 09:50:57 -0400 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 1uk11D-0004cS-Os for qemu-rust@nongnu.org; Thu, 07 Aug 2025 09:50:55 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1uk11B-0000Ls-P7 for qemu-rust@nongnu.org; Thu, 07 Aug 2025 09:50:55 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1754574650; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=PvaorgGh5P0tSa23iMIJ9bc8NLt/ryhr9OaKS4s4BuY=; b=Tdagdu7mp5bMRye1pS1+19Q26dtzzIYkS0fwmh/Iiqs3PJhJ1h5+fUTnJvbTmIHaJDhhBf aqAZxKlUUtdqB/M/byPu1qrdLLmfqtkU0lJUTorqmlRfcYAKcy68ULgki80jaN1iVilDg1 5YXSY2sFD7hCxPCT9pUoeR9TaIZ+CTw= Received: from mail-wm1-f70.google.com (mail-wm1-f70.google.com [209.85.128.70]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-657-5wKbXgCLPeOZkyaZlA1lvA-1; Thu, 07 Aug 2025 09:50:49 -0400 X-MC-Unique: 5wKbXgCLPeOZkyaZlA1lvA-1 X-Mimecast-MFC-AGG-ID: 5wKbXgCLPeOZkyaZlA1lvA_1754574648 Received: by mail-wm1-f70.google.com with SMTP id 5b1f17b1804b1-459d7ed90baso7722755e9.2 for ; Thu, 07 Aug 2025 06:50:49 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1754574648; x=1755179448; h=content-transfer-encoding:in-reply-to:autocrypt:content-language :from:references:cc:to:subject:user-agent:mime-version:date :message-id:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=PvaorgGh5P0tSa23iMIJ9bc8NLt/ryhr9OaKS4s4BuY=; b=JkiPiDfgtR3shfR4Aa5facDKldrSl7WJKHF8FUAKM0osp7qFiAE1Bzt0ZSYfv4xiU1 Jm8iX2e8dU7Wd550DACFZw74gCfHYSYxKBfbecoxpIrogDkLmEgoWRP/pCQAccJ9HC2I ZNGQhEycOzna5n6fbNlY9pk2PauNQfHj81FfugzphtB30oRrJO7udH6WYWowHFTMmC33 bCVfDp3YkQ3w110fmU4Uz0fiHMoc055IZDXR8de9ruqICjwBvCBvtCXTL8/CWjeFOGu1 Ctxszi8hnH2n4k8qforODBBP14AruTtuDZvHC0nDzZgvPViBrXuwFE+itQ23UFdH70Cl OyCQ== X-Forwarded-Encrypted: i=1; AJvYcCVrr2GZvD16/yA3xMYs+NngzYHv+S+YylQ8Qec34HmSjew2P0loDtnv/aakhbV/Xw6C0R8ZLPiP/XQ=@nongnu.org X-Gm-Message-State: AOJu0YyyLXVbKzLwsl+l2HdaZ733u2lIdvG2HPisx9xis0MlmP08Ndy6 Cgg2GUoQHMPJjvoR0mZu/JNAQ9O1jtEwLC61b9/giraQ0zINKHqJQVs/AeYy1zFhkU6M4l2SYSO 5ZPNP/3V82UPHPIUuGZSikQigJU96AOfQMcjxrYl4KL5cVe+UX6rmNhc= X-Gm-Gg: ASbGncsPEAxWEAcDw+5FOA1jzqyeI5AWM24oBLR9LmtggbHqNXbR8rfyBJeXrCoP1Ul dp21Ay9TbXgbDVsPdPHbJbaudMH1jBIJ6CqDf35mcwbJRNnenfujm2RcQ2fvXnUfywaKkIYc85V 4BFrLWZi8k8WzQhTj6oZ1nARsi679XitzLPdlJQbxan9XQKcTtaraFsmZVN3kqCQG5q2rW2zM6I 1VhD5aLqMn8hQ7rw6hqR6aWX+o2LOCaPu9LjywSNREOM6oiHJQcNVackzcol0sZthkYQXXYqCXv gv4r/WwdZJODoRw+hPaVMtvheMaGVG6kkikdpnMIqKA3 X-Received: by 2002:a05:600c:34ce:b0:43c:e70d:44f0 with SMTP id 5b1f17b1804b1-459e78a2d72mr67612775e9.19.1754574648117; Thu, 07 Aug 2025 06:50:48 -0700 (PDT) X-Google-Smtp-Source: AGHT+IGWnCGRUMrYINcgGsMYQVVtZx8JpmqrXEJr4bBJ5kaqWhqrByFa4hggqbjHwXhQjMepngWg+w== X-Received: by 2002:a05:600c:34ce:b0:43c:e70d:44f0 with SMTP id 5b1f17b1804b1-459e78a2d72mr67612405e9.19.1754574647596; Thu, 07 Aug 2025 06:50:47 -0700 (PDT) Received: from [192.168.10.48] ([151.49.253.173]) by smtp.googlemail.com with ESMTPSA id 5b1f17b1804b1-459e58554f2sm92269425e9.12.2025.08.07.06.50.46 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 07 Aug 2025 06:50:46 -0700 (PDT) Message-ID: <3ce35920-919b-4caf-87c5-b92bd603388a@redhat.com> Date: Thu, 7 Aug 2025 15:50:45 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC 24/26] rust/memory: Provide AddressSpace bindings To: Zhao Liu , Peter Xu , David Hildenbrand , =?UTF-8?Q?Philippe_Mathieu-Daud=C3=A9?= , Manos Pitsidianakis , =?UTF-8?Q?Alex_Benn=C3=A9e?= , Thomas Huth , Junjie Mao Cc: qemu-devel@nongnu.org, qemu-rust@nongnu.org, Dapeng Mi , Chuanxiao Dong References: <20250807123027.2910950-1-zhao1.liu@intel.com> <20250807123027.2910950-25-zhao1.liu@intel.com> From: Paolo Bonzini Autocrypt: addr=pbonzini@redhat.com; keydata= xsEhBFRCcBIBDqDGsz4K0zZun3jh+U6Z9wNGLKQ0kSFyjN38gMqU1SfP+TUNQepFHb/Gc0E2 CxXPkIBTvYY+ZPkoTh5xF9oS1jqI8iRLzouzF8yXs3QjQIZ2SfuCxSVwlV65jotcjD2FTN04 hVopm9llFijNZpVIOGUTqzM4U55sdsCcZUluWM6x4HSOdw5F5Utxfp1wOjD/v92Lrax0hjiX DResHSt48q+8FrZzY+AUbkUS+Jm34qjswdrgsC5uxeVcLkBgWLmov2kMaMROT0YmFY6A3m1S P/kXmHDXxhe23gKb3dgwxUTpENDBGcfEzrzilWueOeUWiOcWuFOed/C3SyijBx3Av/lbCsHU Vx6pMycNTdzU1BuAroB+Y3mNEuW56Yd44jlInzG2UOwt9XjjdKkJZ1g0P9dwptwLEgTEd3Fo UdhAQyRXGYO8oROiuh+RZ1lXp6AQ4ZjoyH8WLfTLf5g1EKCTc4C1sy1vQSdzIRu3rBIjAvnC tGZADei1IExLqB3uzXKzZ1BZ+Z8hnt2og9hb7H0y8diYfEk2w3R7wEr+Ehk5NQsT2MPI2QBd wEv1/Aj1DgUHZAHzG1QN9S8wNWQ6K9DqHZTBnI1hUlkp22zCSHK/6FwUCuYp1zcAEQEAAc0j UGFvbG8gQm9uemluaSA8cGJvbnppbmlAcmVkaGF0LmNvbT7CwU0EEwECACMFAlRCcBICGwMH CwkIBwMCAQYVCAIJCgsEFgIDAQIeAQIXgAAKCRB+FRAMzTZpsbceDp9IIN6BIA0Ol7MoB15E 11kRz/ewzryFY54tQlMnd4xxfH8MTQ/mm9I482YoSwPMdcWFAKnUX6Yo30tbLiNB8hzaHeRj jx12K+ptqYbg+cevgOtbLAlL9kNgLLcsGqC2829jBCUTVeMSZDrzS97ole/YEez2qFpPnTV0 VrRWClWVfYh+JfzpXmgyhbkuwUxNFk421s4Ajp3d8nPPFUGgBG5HOxzkAm7xb1cjAuJ+oi/K CHfkuN+fLZl/u3E/fw7vvOESApLU5o0icVXeakfSz0LsygEnekDbxPnE5af/9FEkXJD5EoYG SEahaEtgNrR4qsyxyAGYgZlS70vkSSYJ+iT2rrwEiDlo31MzRo6Ba2FfHBSJ7lcYdPT7bbk9 AO3hlNMhNdUhoQv7M5HsnqZ6unvSHOKmReNaS9egAGdRN0/GPDWr9wroyJ65ZNQsHl9nXBqE AukZNr5oJO5vxrYiAuuTSd6UI/xFkjtkzltG3mw5ao2bBpk/V/YuePrJsnPFHG7NhizrxttB nTuOSCMo45pfHQ+XYd5K1+Cv/NzZFNWscm5htJ0HznY+oOsZvHTyGz3v91pn51dkRYN0otqr bQ4tlFFuVjArBZcapSIe6NV8C4cEiSTOwE0EVEJx7gEIAMeHcVzuv2bp9HlWDp6+RkZe+vtl KwAHplb/WH59j2wyG8V6i33+6MlSSJMOFnYUCCL77bucx9uImI5nX24PIlqT+zasVEEVGSRF m8dgkcJDB7Tps0IkNrUi4yof3B3shR+vMY3i3Ip0e41zKx0CvlAhMOo6otaHmcxr35sWq1Jk tLkbn3wG+fPQCVudJJECvVQ//UAthSSEklA50QtD2sBkmQ14ZryEyTHQ+E42K3j2IUmOLriF dNr9NvE1QGmGyIcbw2NIVEBOK/GWxkS5+dmxM2iD4Jdaf2nSn3jlHjEXoPwpMs0KZsgdU0pP JQzMUMwmB1wM8JxovFlPYrhNT9MAEQEAAcLBMwQYAQIACQUCVEJx7gIbDAAKCRB+FRAMzTZp sadRDqCctLmYICZu4GSnie4lKXl+HqlLanpVMOoFNnWs9oRP47MbE2wv8OaYh5pNR9VVgyhD OG0AU7oidG36OeUlrFDTfnPYYSF/mPCxHttosyt8O5kabxnIPv2URuAxDByz+iVbL+RjKaGM GDph56ZTswlx75nZVtIukqzLAQ5fa8OALSGum0cFi4ptZUOhDNz1onz61klD6z3MODi0sBZN Aj6guB2L/+2ZwElZEeRBERRd/uommlYuToAXfNRdUwrwl9gRMiA0WSyTb190zneRRDfpSK5d usXnM/O+kr3Dm+Ui+UioPf6wgbn3T0o6I5BhVhs4h4hWmIW7iNhPjX1iybXfmb1gAFfjtHfL xRUr64svXpyfJMScIQtBAm0ihWPltXkyITA92ngCmPdHa6M1hMh4RDX+Jf1fiWubzp1voAg0 JBrdmNZSQDz0iKmSrx8xkoXYfA3bgtFN8WJH2xgFL28XnqY4M6dLhJwV3z08tPSRqYFm4NMP dRsn0/7oymhneL8RthIvjDDQ5ktUjMe8LtHr70OZE/TT88qvEdhiIVUogHdo4qBrk41+gGQh b906Dudw5YhTJFU3nC6bbF2nrLlB4C/XSiH76ZvqzV0Z/cAMBo5NF/w= In-Reply-To: <20250807123027.2910950-25-zhao1.liu@intel.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: 6f_8oYUPd9BO9BVad5sES1as4oPFOT9oaElxVGlXtn4_1754574648 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=170.10.129.124; envelope-from=pbonzini@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, 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_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-rust@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: QEMU Rust-related patches and discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-rust-bounces+qemu-rust=archiver.kernel.org@nongnu.org Sender: qemu-rust-bounces+qemu-rust=archiver.kernel.org@nongnu.org On 8/7/25 14:30, Zhao Liu wrote: > +impl GuestAddressSpace for AddressSpace { > + type M = FlatView; > + type T = FlatViewRefGuard; > + > + /// Get the memory of the [`AddressSpace`]. > + /// > + /// This function retrieves the [`FlatView`] for the current > + /// [`AddressSpace`]. And it should be called from an RCU > + /// critical section. The returned [`FlatView`] is used for > + /// short-term memory access. > + /// > + /// Note, this function method may **panic** if [`FlatView`] is > + /// being distroying. Fo this case, we should consider to providing > + /// the more stable binding with [`bindings::address_space_get_flatview`]. > + fn memory(&self) -> Self::T { > + let flatp = unsafe { address_space_to_flatview(self.0.as_mut_ptr()) }; > + FlatViewRefGuard::new(unsafe { Self::M::from_raw(flatp) }).expect( > + "Failed to clone FlatViewRefGuard: the FlatView may have been destroyed concurrently.", > + ) This is essentially address_space_get_flatview(). You can call it directly, or you need to loop if FlatViewRefGuard finds a zero reference count. > + } > +} > + > +impl AddressSpace { > + /// The write interface of `AddressSpace`. > + /// > + /// This function is similar to `address_space_write` in C side. > + /// > + /// But it assumes the memory attributes is MEMTXATTRS_UNSPECIFIED. > + pub fn write(&self, buf: &[u8], addr: GuestAddress) -> Result { > + rcu_read_lock(); > + let r = self.memory().deref().write(buf, addr); > + rcu_read_unlock(); self.memory() must not need rcu_read_lock/unlock around it, they should be called by the memory() function itself. > + r.map_err(guest_mem_err_to_qemu_err) > + } I think it's ok to return the vm-memory error. Ultimately, the error will be either ignored or turned into a device error condition, but I don't think it's ever going to become an Error**. > + /// The store interface of `AddressSpace`. > + /// > + /// This function is similar to `address_space_st{size}` in C side. > + /// > + /// But it only assumes @val follows target-endian by default. So ensure > + /// the endian of `val` aligned with target, before using this method. QEMU is trying to get rid of target endianness. We should use the vm-memory BeNN and LeNN as much as possible. It would be great if you could write either ADDRESS_SPACE_MEMORY.store::(addr, 42); or let n = Le32(42); ADDRESS_SPACE_MEMORY.store(addr, n); but not ADDRESS_SPACE_MEMORY.store(addr, 42); (Also I've not looked at the patches closely enough, but wouldn't store() use *host* endianness? Same in patch 23). Paolo > + /// And it assumes the memory attributes is MEMTXATTRS_UNSPECIFIED. > + pub fn store(&self, addr: GuestAddress, val: T) -> Result<()> { > + rcu_read_lock(); > + let r = self.memory().deref().store(val, addr, Ordering::Relaxed); > + rcu_read_unlock(); > + r.map_err(guest_mem_err_to_qemu_err) > + } > + > + /// The load interface of `AddressSpace`. > + /// > + /// This function is similar to `address_space_ld{size}` in C side. > + /// > + /// But it only support target-endian by default. The returned value is > + /// with target-endian. > + /// > + /// And it assumes the memory attributes is MEMTXATTRS_UNSPECIFIED. > + pub fn load(&self, addr: GuestAddress) -> Result { > + rcu_read_lock(); > + let r = self.memory().deref().load(addr, Ordering::Relaxed); > + rcu_read_unlock(); > + r.map_err(guest_mem_err_to_qemu_err) > + } > +} > + > +/// The safe binding around [`bindings::address_space_memory`]. > +/// > +/// `ADDRESS_SPACE_MEMORY` provides the complete address space > +/// abstraction for the whole Guest memory. > +pub static ADDRESS_SPACE_MEMORY: &AddressSpace = unsafe { > + let ptr: *const bindings::AddressSpace = addr_of!(address_space_memory); > + > + // SAFETY: AddressSpace is #[repr(transparent)]. > + let wrapper_ptr: *const AddressSpace = ptr.cast(); > + > + // SAFETY: `address_space_memory` structure is valid in C side during > + // the whole QEMU life. > + &*wrapper_ptr > +};