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 19E7AE77184 for ; Thu, 19 Dec 2024 16:23:11 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1tOJFP-0001mG-Vs; Thu, 19 Dec 2024 11:19:36 -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 1tOGw5-0007Hg-Ah for qemu-devel@nongnu.org; Thu, 19 Dec 2024 08:51:29 -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 1tOGw3-0001LH-Kh for qemu-devel@nongnu.org; Thu, 19 Dec 2024 08:51:29 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1734616285; 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=hAXXvvOkklGkw9sjph4RvQEZTmWxQ6bkUycqSZlViZ0=; b=cUJv4kZWjzFsI7CMvJEDxgPDDLtbZyfzihWTWVKvlhMlWCnHnxGxrYoPKOuZN7yJQOQYmy 5hXOTJylO90G9lLs46sazsfBruAne5fWfLBwipqxQebHVoJztTeUpeBeknZtGENU5wM262 Z3FJaLPmOyhYzB4vPl2PjmyWPHSX2Vs= Received: from mail-wm1-f69.google.com (mail-wm1-f69.google.com [209.85.128.69]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-126-0FesnXQRPIWAbR4lC82Ljw-1; Thu, 19 Dec 2024 08:51:24 -0500 X-MC-Unique: 0FesnXQRPIWAbR4lC82Ljw-1 X-Mimecast-MFC-AGG-ID: 0FesnXQRPIWAbR4lC82Ljw Received: by mail-wm1-f69.google.com with SMTP id 5b1f17b1804b1-4361fc2b2d6so5034185e9.3 for ; Thu, 19 Dec 2024 05:51:24 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1734616283; x=1735221083; h=content-transfer-encoding:in-reply-to:organization: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=hAXXvvOkklGkw9sjph4RvQEZTmWxQ6bkUycqSZlViZ0=; b=rLozZen2UDug2DatECnBEcWvK4gLZA41CFQRrGj/rTGhb5t83lh2qY6irqqblLCIWz BMqTgg2uJ/b3Ta/TSDyNU0mTTUN4JpC1GJMnVrUMDThxR2tOtd8WzRd0AmxHw5sac8fU u69mY8ra1FSi96o4gX1gDZBmWDkVHjlORyj2pimvtPQyLoLLfOtUtR//5u/h16eoJxKc M9MRPyBuXOLDn7+3twOW6CoaO2E7hyJRh01fVfp2+Xdk2fhSms1FypO0YVYiCLVGq69B MnXTuaSDf3BD7m2OC1DkK6X6P9hagf9TRSYFHwBMKlJzeBUXXg3wd4d/SNK4S9PCTLLK IU8Q== X-Forwarded-Encrypted: i=1; AJvYcCVcQ6dwwnnUATSPORmE0TwulwZy2y7WX4HhOJkO4YiOV/V/8q/arQBov9mnhm7y57SIWpoT+WdFc71A@nongnu.org X-Gm-Message-State: AOJu0Ywf/6UcYa1+8IxwO39UNe7PF4UnMFezdkQvgz1FI04sZbEzpJUM Nrbv+yeYOOqYWMSBVZ2KBNWMq+MghBUUmLU+HyEDFclDmoTfhvIPX3g+ld3X68arIrRj7w7Tzta ISrIMa9XvkmtQkM9hMAhp8wXX4wmFw6TEHSwR24vEENh3YS+qE0k3 X-Gm-Gg: ASbGncsKNFg1TMMOQW4jZN1tDWX0OV2Gt1BYxBV4/s5VmBE4lG+mEC3uNshsZ8yT/0E 4KxMkhUK+8KmN4PwAxgbdoKlfBa6auyXm6g/bpYw5y7aH5RNnkLDybGvFXw0/pHE3OirKiygrGx WHeomJgaW5MzVHiWwCXrC/o03WOwEm5TqWPQwr3jV2syPFmumqW3GLH9Rmn9OCfKl6kd7kbzF0H 66j4v9u/xpo3DhiHS9Z6btW1YNNOPSEMFYVnlDPisZtejVWALlczEWZHQJR11yntctNS94KNOvP 55CRS3M3keSDzSekf47tK6R/sTbQATGORpIY1YVtmqQ4O4tv9TV1vXteF3JL6YFSMRQUA9wOpY6 q0b5Rfw== X-Received: by 2002:a05:6000:4010:b0:385:f7a3:fea6 with SMTP id ffacd0b85a97d-38a19b08171mr3150471f8f.13.1734616283351; Thu, 19 Dec 2024 05:51:23 -0800 (PST) X-Google-Smtp-Source: AGHT+IHXM+lBMWPWLQThprfVGv8fy+Ns4/aWKeXlcJoMDWPYLUFJGL5ivoXjtSc1HpZsG8esdpQILQ== X-Received: by 2002:a05:6000:4010:b0:385:f7a3:fea6 with SMTP id ffacd0b85a97d-38a19b08171mr3150460f8f.13.1734616282955; Thu, 19 Dec 2024 05:51:22 -0800 (PST) Received: from ?IPV6:2003:cb:c749:6600:b73a:466c:e610:686? (p200300cbc7496600b73a466ce6100686.dip0.t-ipconnect.de. [2003:cb:c749:6600:b73a:466c:e610:686]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-38a1c89e219sm1619492f8f.84.2024.12.19.05.51.22 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 19 Dec 2024 05:51:22 -0800 (PST) Message-ID: Date: Thu, 19 Dec 2024 14:51:21 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] hw/virtio: reset virtio balloon stats on machine reset To: =?UTF-8?Q?Daniel_P=2E_Berrang=C3=A9?= , qemu-devel@nongnu.org Cc: "Michael S. Tsirkin" References: <20241218172912.4170899-1-berrange@redhat.com> From: David Hildenbrand Content-Language: en-US Autocrypt: addr=david@redhat.com; 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 B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzSREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZgEEwEIAEICGwMGCwkIBwMCBhUIAgkKCwQW AgMBAh4BAheAAhkBFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl8Ox4kFCRKpKXgACgkQTd4Q 9wD/g1oHcA//a6Tj7SBNjFNM1iNhWUo1lxAja0lpSodSnB2g4FCZ4R61SBR4l/psBL73xktp rDHrx4aSpwkRP6Epu6mLvhlfjmkRG4OynJ5HG1gfv7RJJfnUdUM1z5kdS8JBrOhMJS2c/gPf wv1TGRq2XdMPnfY2o0CxRqpcLkx4vBODvJGl2mQyJF/gPepdDfcT8/PY9BJ7FL6Hrq1gnAo4 3Iv9qV0JiT2wmZciNyYQhmA1V6dyTRiQ4YAc31zOo2IM+xisPzeSHgw3ONY/XhYvfZ9r7W1l pNQdc2G+o4Di9NPFHQQhDw3YTRR1opJaTlRDzxYxzU6ZnUUBghxt9cwUWTpfCktkMZiPSDGd KgQBjnweV2jw9UOTxjb4LXqDjmSNkjDdQUOU69jGMUXgihvo4zhYcMX8F5gWdRtMR7DzW/YE BgVcyxNkMIXoY1aYj6npHYiNQesQlqjU6azjbH70/SXKM5tNRplgW8TNprMDuntdvV9wNkFs 9TyM02V5aWxFfI42+aivc4KEw69SE9KXwC7FSf5wXzuTot97N9Phj/Z3+jx443jo2NR34XgF 89cct7wJMjOF7bBefo0fPPZQuIma0Zym71cP61OP/i11ahNye6HGKfxGCOcs5wW9kRQEk8P9 M/k2wt3mt/fCQnuP/mWutNPt95w9wSsUyATLmtNrwccz63XOwU0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAHCwXwEGAEIACYCGwwWIQQb2cqtc1xMOkYN/MpN3hD3 AP+DWgUCXw7HsgUJEqkpoQAKCRBN3hD3AP+DWrrpD/4qS3dyVRxDcDHIlmguXjC1Q5tZTwNB boaBTPHSy/Nksu0eY7x6HfQJ3xajVH32Ms6t1trDQmPx2iP5+7iDsb7OKAb5eOS8h+BEBDeq 3ecsQDv0fFJOA9ag5O3LLNk+3x3q7e0uo06XMaY7UHS341ozXUUI7wC7iKfoUTv03iO9El5f XpNMx/YrIMduZ2+nd9Di7o5+KIwlb2mAB9sTNHdMrXesX8eBL6T9b+MZJk+mZuPxKNVfEQMQ a5SxUEADIPQTPNvBewdeI80yeOCrN+Zzwy/Mrx9EPeu59Y5vSJOx/z6OUImD/GhX7Xvkt3kq Er5KTrJz3++B6SH9pum9PuoE/k+nntJkNMmQpR4MCBaV/J9gIOPGodDKnjdng+mXliF3Ptu6 3oxc2RCyGzTlxyMwuc2U5Q7KtUNTdDe8T0uE+9b8BLMVQDDfJjqY0VVqSUwImzTDLX9S4g/8 kC4HRcclk8hpyhY2jKGluZO0awwTIMgVEzmTyBphDg/Gx7dZU1Xf8HFuE+UZ5UDHDTnwgv7E th6RC9+WrhDNspZ9fJjKWRbveQgUFCpe1sa77LAw+XFrKmBHXp9ZVIe90RMe2tRL06BGiRZr jPrnvUsUUsjRoRNJjKKA/REq+sAnhkNPPZ/NNMjaZ5b8Tovi8C0tmxiCHaQYqj7G2rgnT0kt WNyWQQ== Organization: Red Hat In-Reply-To: <20241218172912.4170899-1-berrange@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=170.10.133.124; envelope-from=david@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -31 X-Spam_score: -3.2 X-Spam_bar: --- X-Spam_report: (-3.2 / 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_H2=-1.116, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_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-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 On 18.12.24 18:29, Daniel P. Berrangé wrote: > When a machine is first booted, all virtio balloon stats are initialized > to their default value -1 (18446744073709551615 when represented as > unsigned). > > They remain that way while the firmware is loading, and early phase of > guest OS boot, until the virtio-balloon driver is activated. Thereafter > the reported stats reflect the guest OS activity. > > When a machine reset is performed, however, the virtio-balloon stats are > left unchanged by QEMU, despite the guest OS no longer updating them, > nor indeed even still existing. > > IOW, the mgmt app keeps getting stale stats until the guest OS starts > once more and loads the virtio-balloon driver (if ever). At that point > the app will see a discontinuity in the reported values as they sudden > jump from the stale value to the new value. This jump is indigituishable > from a valid data update. > > While there is an "last-updated" field to report on the freshness of > the stats, that does not unambiguously tell the mgmt app whether the > stats are still conceptually relevant to the current running workload. > > It is more conceptually useful to reset the stats to their default > values on machine reset, given that the previous guest workload the > stats reflect no longer exists. The mgmt app can now clearly identify > that there are is no stats information available from the current > executing workload. > > The 'last-updated' time is also reset back to 0. > > IOW, on every machine reset, the virtio stats are in the same clean > state they were when the macine first powered on. > > A functional test is added to validate this behaviour with a real > world guest OS. > > Signed-off-by: Daniel P. Berrangé > --- > > One side-thought I have, is whether it makes sense to add a > 'reset-count' field in the virtio stats, alongside the > 'last-updated' field. While apps can infer a reset from seeing > the stats all go back to their defaults, an explicit flag is > simpler... > > MAINTAINERS | 1 + > hw/virtio/virtio-balloon.c | 30 ++++- > include/hw/virtio/virtio-balloon.h | 4 + > tests/functional/test_virtio_balloon.py | 161 ++++++++++++++++++++++++ > 4 files changed, 195 insertions(+), 1 deletion(-) > create mode 100755 tests/functional/test_virtio_balloon.py > > diff --git a/MAINTAINERS b/MAINTAINERS > index 822f34344b..1380d53d03 100644 > --- a/MAINTAINERS > +++ b/MAINTAINERS > @@ -2234,6 +2234,7 @@ F: include/hw/virtio/virtio-balloon.h > F: system/balloon.c > F: include/sysemu/balloon.h > F: tests/qtest/virtio-balloon-test.c > +F: tests/functional/test_virtio_balloon.py > > virtio-9p > M: Greg Kurz > diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c > index ab2ee30475..fe0854e198 100644 > --- a/hw/virtio/virtio-balloon.c > +++ b/hw/virtio/virtio-balloon.c > @@ -31,7 +31,7 @@ > #include "trace.h" > #include "qemu/error-report.h" > #include "migration/misc.h" > - > +#include "sysemu/reset.h" > #include "hw/virtio/virtio-bus.h" > #include "hw/virtio/virtio-access.h" > > @@ -910,6 +910,8 @@ static void virtio_balloon_device_realize(DeviceState *dev, Error **errp) > } > > reset_stats(s); > + s->stats_last_update = 0; > + qemu_register_resettable(OBJECT(dev)); > } > > static void virtio_balloon_device_unrealize(DeviceState *dev) > @@ -917,6 +919,7 @@ static void virtio_balloon_device_unrealize(DeviceState *dev) > VirtIODevice *vdev = VIRTIO_DEVICE(dev); > VirtIOBalloon *s = VIRTIO_BALLOON(dev); > > + qemu_unregister_resettable(OBJECT(dev)); > if (s->free_page_bh) { > qemu_bh_delete(s->free_page_bh); > object_unref(OBJECT(s->iothread)); > @@ -987,6 +990,27 @@ static void virtio_balloon_set_status(VirtIODevice *vdev, uint8_t status) > } > } Using qemu_register_resettable() can have unfortunate side effects that this code is triggered when the device is reset, not necessarily when the complete machine. For virtio-mem at least that's an issue, and here is how I'll fix it: https://lore.kernel.org/qemu-devel/20241218105303.1966303-2-david@redhat.com/ -- Cheers, David / dhildenb