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Wed, 12 Feb 2025 01:28:41 -0800 (PST) X-Google-Smtp-Source: AGHT+IFTkzorP4BAe0HGS1kf4MbmBwnv1+OK3RKrArrwWo0Q0z6JpMmyP2/t0Z24AsbZpLdgSOg4Lg== X-Received: by 2002:a05:600c:4e8d:b0:439:554f:f64f with SMTP id 5b1f17b1804b1-439580e7b8bmr23926905e9.0.1739352521255; Wed, 12 Feb 2025 01:28:41 -0800 (PST) Received: from [192.168.10.81] ([151.95.148.6]) by smtp.googlemail.com with ESMTPSA id ffacd0b85a97d-38dcd0fac67sm13905279f8f.54.2025.02.12.01.28.40 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 12 Feb 2025 01:28:40 -0800 (PST) Message-ID: <533ac9c1-7486-4b1b-af9a-ed4a864727de@redhat.com> Date: Wed, 12 Feb 2025 10:28:39 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 04/11] rust/qemu-api: Add wrappers to run futures in QEMU To: Kevin Wolf , qemu-block@nongnu.org Cc: hreitz@redhat.com, manos.pitsidianakis@linaro.org, qemu-devel@nongnu.org, qemu-rust@nongnu.org References: <20250211214328.640374-1-kwolf@redhat.com> <20250211214328.640374-5-kwolf@redhat.com> From: Paolo Bonzini Autocrypt: addr=pbonzini@redhat.com; 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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: -35 X-Spam_score: -3.6 X-Spam_bar: --- X-Spam_report: (-3.6 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1.54, 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_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_NONE=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: , X-List-Received-Date: Wed, 12 Feb 2025 09:28:50 -0000 On 2/11/25 22:43, Kevin Wolf wrote: > +/// Use QEMU's event loops to run a Rust [`Future`] to completion and return its result. > +/// > +/// This function must be called in coroutine context. If the future isn't ready yet, it yields. > +pub fn qemu_co_run_future(future: F) -> F::Output { > + let waker = Arc::new(RunFutureWaker { > + co: unsafe { bindings::qemu_coroutine_self() }, > + }) > + .into(); into what? :) Maybe you can add the type to the "let" for clarity. > + let mut cx = Context::from_waker(&waker); > + > + let mut pinned_future = std::pin::pin!(future); > + loop { > + match pinned_future.as_mut().poll(&mut cx) { > + Poll::Ready(res) => return res, Alternatively, "break res" (matter of taste). > + Poll::Pending => unsafe { > + bindings::qemu_coroutine_yield(); > + }, > + } > + } > +} > +/// Wrapper around [`qemu_co_run_future`] that can be called from C. > +/// > +/// # Safety > +/// > +/// `future` must be a valid pointer to an owned `F` (it will be freed in this function). `output` > +/// must be a valid pointer representing a mutable reference to an `F::Output` where the result can > +/// be stored. > +unsafe extern "C" fn rust_co_run_future( > + future: *mut bindings::RustBoxedFuture, > + output: *mut c_void, > +) { > + let future = unsafe { Box::from_raw(future.cast::()) }; > + let output = output.cast::(); > + let ret = qemu_co_run_future(*future); > + unsafe { > + *output = ret; This should use output.write(ret), to ensure that the output is written without dropping the previous value. Also, would qemu_co_run_future() and qemu_run_future() become methods on an Executor later? Maybe it make sense to have already something like pub trait QemuExecutor { fn run_until(future: F) -> F::Output; } pub struct Executor; pub struct CoExecutor; and pass an executor to Rust functions (&Executor for no_coroutine_fn, &CoExecutor for coroutine_fn, &dyn QemuExecutor for mixed). Or would that be premature in your opinion? Paolo