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 8E7F03D649F; Wed, 24 Jun 2026 14:57:08 +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=1782313029; cv=none; b=Q0czvSE3AeFnXEGYeBVklt2HA/DIle57qK5ACwbaRR69oSGByPAW2cEIOxNAxN1fANbjGXQAoJ+HvUMPSR9J67JxbdXP3FulsV+aQLX0COXuJukW6Tm/ajswGYy1WAMJHb9O+59Z9gnofWnxejqv8ax3SLO+Q4koqRCj/lugGCU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782313029; c=relaxed/simple; bh=+9wTEKkdEzQYQbT8eo8XRM0xiY+dzS2MODh7/s251dE=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=JwrOvsjFMpkJc8RMbWYA/rHAuuqpSlWxsdZoJ2KeH9ZIUP5G6ZmZGhBSTL11aTy/1oWYIKSWeRCYssGI5BNrGUeh/Mt/LgI9yi6Ociadjd7U7Vfb/dqI2clfjBGsYI6JDEjiFVXn5JI9g0wROM4k0Xk8lsQvh8qUO4BsSvdY0Kk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Iy3DLWGI; 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="Iy3DLWGI" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 22FC51F000E9; Wed, 24 Jun 2026 14:57:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1782313028; bh=CoAuMsFOoDWwixh0zvxsjRnHJH2OzDStPjK5FlR4YIY=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=Iy3DLWGIAM9t0zGL5xDZHJOzugsNWis6X4kDbdkZTdkGE4Ti9skANZwMWzK7EWI/e 7Lsv2mSfrUDIksJ5q6POiMk0Vxo/bcSLlQCI6LwiUWv2ag9f8mh6me300Wgubu0PO6 CZGuYLwE/AxlkDrMxloUsGF7ubQgO0KVQ9NNhVYbOHPpBDJX9TJyR8N/qcQ+LK62GV +bfvGtF29gLcwz4a7ucc0VxzI54oFh0nMScxOKAV/SaZcp9vdH+Zjx2/v46f4TfYKY hPgdoTtfH7V2t5YAGHsvJhNi/TvPfNKAuqAX+6M4mrynEPjSXPzQhWnQ36M+rP3PbP 5xc3o9t+WWL2w== Message-ID: <549e5456-2b6c-48a5-abe5-ef5425c3f63c@kernel.org> Date: Wed, 24 Jun 2026 16:57:05 +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 v2 4/4] virtio_balloon: warn on failed buffer add in tell_host() To: "Denis V. Lunev" , mst@redhat.com Cc: virtualization@lists.linux.dev, linux-kernel@vger.kernel.org References: <20260624140846.2616797-1-den@openvz.org> <20260624140846.2616797-5-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: <20260624140846.2616797-5-den@openvz.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 6/24/26 16:08, Denis V. Lunev wrote: > tell_host() ignores the return value of virtqueue_add_outbuf() and goes > on to kick the queue and wait_event() for the host's ack. The comment > claims "We should always be able to add one buffer to an empty queue", > but that does not hold once the virtqueue has been broken (e.g. on > device shutdown): the add then fails with -EIO and the following > wait_event() would block forever on a buffer the host can never return. > > Warn and bail out on failure, mirroring virtballoon_free_page_report(). > > Suggested-by: David Hildenbrand > Signed-off-by: Denis V. Lunev > --- > drivers/virtio/virtio_balloon.c | 6 ++++-- > 1 file changed, 4 insertions(+), 2 deletions(-) > > diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c > index 26fc3c40d5b2..0866a8781f0b 100644 > --- a/drivers/virtio/virtio_balloon.c > +++ b/drivers/virtio/virtio_balloon.c > @@ -184,16 +184,18 @@ static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq) > { > struct scatterlist sg; > unsigned int len; > + int err; > > sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns); > > /* We should always be able to add one buffer to an empty queue. */ > - virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL); > + err = virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL); > + if (WARN_ON_ONCE(err)) > + return; > virtqueue_kick(vq); > > /* When host has read buffer, this completes via balloon_ack */ > wait_event(vb->acked, virtqueue_get_buf(vq, &len)); > - > } We have another uncheck instance in stats_handle_request(), what about that one? -- Cheers, David