From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 28D7F3B3BE1; Mon, 22 Jun 2026 14:38:57 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782139138; cv=none; b=Pq8ZrOnKf4hwTZR/hKdXyyYNt7k7OpnEZkD/NdhF04QwkaNcxGICPFzyJr+Ab0IPZ6JSdW0LRTVNa7eMLfMWCMeOG1N89RdFu7+62G4grkVQbA9b3vpfQATtsuB3+4IZXtlY+bkmUlac7KMTfgWD2Wa4yILcqSaQQ9XIFSjFLcI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782139138; c=relaxed/simple; bh=OyKSR115bKLYHAyLUX7MNavqBz7tPhevDZSM768E/9w=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=LBA0fZPa3y5sa5UHlunK2z+rqnC7gboicTL53c5vIR34neMpfybtnFKuYNPwM+VMc7rVt70pzuP6krnC7Jy2usJVIYbIB57F6sF2hhwmKSkcAFxv+xMvCfgiNWiBJYBA7i7xfAH0i5cpms0YADpvGcjgNf4S1dtIoQRJFr0Xh8Y= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Si6PYAEJ; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Si6PYAEJ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9D63E1F000E9; Mon, 22 Jun 2026 14:38:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1782139136; bh=aIy5JYqqyN4lYGAvP4PJprQOXNEO2nmNgN+8COp28Ek=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=Si6PYAEJ2qenlLjzIgr2SUvuMEmogWISUNZ00oYOfxMrvnIjP74b7IA6qaXnIit42 NLmQux6I9G4j+E2P3nVkQs6CISG6nYfsGwsYqt8McQT0uEkfyl+46eAJxdq2YxiLGz C7UDOSsdcOLRwkhybsikKsrJcHFYMB79JoloL8LLD90oqrTa62jtB2X3rihbyghah9 Cl2o4JnV2F9o7G0NS63R+ypJ82fAJPeD+n/kjwFHRLPUhNp7g7RYJjGanVuThFUPwM 9xZWeBP5m1grUkUJI4DN3KG0eWmK586dZx3yLI25zFPOe+tV/4V6rg1gIKCIy/UBEz r0OtwrCz/zQ2g== Message-ID: <8b83f251-3a3e-4fc9-8ea9-8d101fb92919@kernel.org> Date: Mon, 22 Jun 2026 16:38:54 +0200 Precedence: bulk X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 2/2] virtio_balloon: quiesce balloon work before device shutdown To: "Denis V. Lunev" , mst@redhat.com Cc: virtualization@lists.linux.dev, linux-kernel@vger.kernel.org References: <20260622133715.3707707-1-den@openvz.org> <20260622133715.3707707-3-den@openvz.org> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzS5EYXZpZCBIaWxk ZW5icmFuZCAoQ3VycmVudCkgPGRhdmlkQGtlcm5lbC5vcmc+wsGQBBMBCAA6AhsDBQkmWAik AgsJBBUKCQgCFgICHgUCF4AWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaYJt/AIZAQAKCRBN 3hD3AP+DWriiD/9BLGEKG+N8L2AXhikJg6YmXom9ytRwPqDgpHpVg2xdhopoWdMRXjzOrIKD g4LSnFaKneQD0hZhoArEeamG5tyo32xoRsPwkbpIzL0OKSZ8G6mVbFGpjmyDLQCAxteXCLXz ZI0VbsuJKelYnKcXWOIndOrNRvE5eoOfTt2XfBnAapxMYY2IsV+qaUXlO63GgfIOg8RBaj7x 3NxkI3rV0SHhI4GU9K6jCvGghxeS1QX6L/XI9mfAYaIwGy5B68kF26piAVYv/QZDEVIpo3t7 /fjSpxKT8plJH6rhhR0epy8dWRHk3qT5tk2P85twasdloWtkMZ7FsCJRKWscm1BLpsDn6EQ4 jeMHECiY9kGKKi8dQpv3FRyo2QApZ49NNDbwcR0ZndK0XFo15iH708H5Qja/8TuXCwnPWAcJ DQoNIDFyaxe26Rx3ZwUkRALa3iPcVjE0//TrQ4KnFf+lMBSrS33xDDBfevW9+Dk6IISmDH1R HFq2jpkN+FX/PE8eVhV68B2DsAPZ5rUwyCKUXPTJ/irrCCmAAb5Jpv11S7hUSpqtM/6oVESC 3z/7CzrVtRODzLtNgV4r5EI+wAv/3PgJLlMwgJM90Fb3CB2IgbxhjvmB1WNdvXACVydx55V7 LPPKodSTF29rlnQAf9HLgCphuuSrrPn5VQDaYZl4N/7zc2wcWM7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: <20260622133715.3707707-3-den@openvz.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 6/22/26 15:37, Denis V. Lunev wrote: > Commit 8bd2fa086a04 ("virtio: break and reset virtio devices on > device_shutdown()") added a generic virtio bus .shutdown handler that > breaks and resets every virtio device during device_shutdown(), i.e. on > reboot and kexec. > > virtio_balloon provides no .shutdown of its own, so that generic path > runs while the balloon's asynchronous work is still armed. Once the > device has been broken, virtqueue_add_inbuf() in > virtballoon_free_page_report() returns -EIO and trips its > WARN_ON_ONCE(). On a kernel booted with panic_on_warn that turns an > ordinary reboot, for example a kexec based upgrade, into a fatal panic > in the middle of device_shutdown(), so the machine never reaches the > new kernel. > > Relaxing that single WARN_ON_ONCE() would only hide the symptom: the > inflate/deflate and OOM paths do not warn, they call > wait_event(vb->acked, ...) and would instead block forever on a broken > queue that can no longer complete. The device has to be quiesced, not > just kept quiet. Ah, so /* We should always be able to add one buffer to an empty queue. */ virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL); is not actually correct. Yeah, quiescing sounds cleaner, although I am thinking whether we should also warn if virtqueue_add_outbuf() fails, similar to what we do in virtballoon_free_page_report(). > > Add a .shutdown handler that quiesces the balloon via the shared > virtballoon_quiesce() helper while the device is still alive, and only > then breaks and resets it. The break and reset are repeated here rather > than reused from virtio_dev_shutdown(): drv->shutdown replaces the > generic handler rather than augmenting it, so that drivers such as > virtio-gpu can opt out of the reset. Unlike virtballoon_remove() the > balloon workqueue is not destroyed, as shutdown does not free the > device and cancel_work_sync() together with stop_update already prevent > any further work from being queued. > > Fixes: 8bd2fa086a04 ("virtio: break and reset virtio devices on device_shutdown()") > Signed-off-by: Denis V. Lunev > --- > drivers/virtio/virtio_balloon.c | 10 ++++++++++ > 1 file changed, 10 insertions(+) > > diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c > index 5b02d9191ac6..e35ada767b4b 100644 > --- a/drivers/virtio/virtio_balloon.c > +++ b/drivers/virtio/virtio_balloon.c > @@ -1137,6 +1137,15 @@ static void virtballoon_remove(struct virtio_device *vdev) > kfree(vb); > } > > +static void virtballoon_shutdown(struct virtio_device *vdev) > +{ > + virtballoon_quiesce(vdev->priv); > + > + virtio_break_device(vdev); > + virtio_synchronize_cbs(vdev); > + vdev->config->reset(vdev); I guess it would be good if we wouldn't have to copy what the default handler does, but could instead just have it in a reusable core function? > +} > + -- Cheers, David