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[2003:cb:c74b:e00:9c12:cdf2:bf1c:b8ed]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-429ed650903sm140416355e9.18.2024.08.20.04.40.26 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 20 Aug 2024 04:40:27 -0700 (PDT) Message-ID: <6ab58af7-3584-40b5-b56c-45544a06c7af@redhat.com> Date: Tue, 20 Aug 2024 13:40:26 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 2/4] reset: Add RESET_TYPE_WAKEUP To: Juraj Marcin , Peter Maydell Cc: qemu-devel@nongnu.org References: <20240813153922.311788-1-jmarcin@redhat.com> <20240813153922.311788-3-jmarcin@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: 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: -21 X-Spam_score: -2.2 X-Spam_bar: -- X-Spam_report: (-2.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.144, 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_H4=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, T_SCC_BODY_TEXT_LINE=-0.01 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 14.08.24 14:32, Juraj Marcin wrote: > On Tue, Aug 13, 2024 at 6:37 PM Peter Maydell wrote: >> >> On Tue, 13 Aug 2024 at 16:39, Juraj Marcin wrote: >>> >>> Some devices need to distinguish cold start reset from waking up from a >>> suspended state. This patch adds new value to the enum, and updates the >>> i386 wakeup method to use this new reset type. >>> >>> Signed-off-by: Juraj Marcin >>> Reviewed-by: David Hildenbrand >>> --- >>> docs/devel/reset.rst | 8 ++++++++ >>> hw/i386/pc.c | 2 +- >>> include/hw/resettable.h | 2 ++ >>> 3 files changed, 11 insertions(+), 1 deletion(-) >>> >>> diff --git a/docs/devel/reset.rst b/docs/devel/reset.rst >>> index 9746a4e8a0..a7c9467313 100644 >>> --- a/docs/devel/reset.rst >>> +++ b/docs/devel/reset.rst >>> @@ -44,6 +44,14 @@ The Resettable interface handles reset types with an enum ``ResetType``: >>> value on each cold reset, such as RNG seed information, and which they >>> must not reinitialize on a snapshot-load reset. >>> >>> +``RESET_TYPE_WAKEUP`` >>> + This type is called for a reset when the system is being woken-up from a >>> + suspended state using the ``qemu_system_wakeup()`` function. If the machine >>> + needs to reset its devices in its ``MachineClass::wakeup()`` method, this >>> + reset type should be used, so devices can differentiate system wake-up from >>> + other reset types. For example, a virtio-mem device must not unplug its >>> + memory during wake-up as that would clear the guest RAM. >>> + >>> Devices which implement reset methods must treat any unknown ``ResetType`` >>> as equivalent to ``RESET_TYPE_COLD``; this will reduce the amount of >>> existing code we need to change if we add more types in future. >>> diff --git a/hw/i386/pc.c b/hw/i386/pc.c >>> index ccb9731c91..49efd0a997 100644 >>> --- a/hw/i386/pc.c >>> +++ b/hw/i386/pc.c >>> @@ -1716,7 +1716,7 @@ static void pc_machine_reset(MachineState *machine, ResetType type) >>> static void pc_machine_wakeup(MachineState *machine) >>> { >>> cpu_synchronize_all_states(); >>> - pc_machine_reset(machine, RESET_TYPE_COLD); >>> + pc_machine_reset(machine, RESET_TYPE_WAKEUP); >>> cpu_synchronize_all_post_reset(); >>> } >> >> I'm happy (following discussion in the previous thread) >> that 'wakeup' is the right reset event to be using here. >> But looking at the existing code for qemu_system_wakeup() >> something seems odd here. qemu_system_wakeup() calls >> the MachineClass::wakeup method if it's set, and does >> nothing if it's not. The PC implementation of that calls >> pc_machine_reset(), which does a qemu_devices_reset(), >> which does a complete three-phase reset of the system. >> But if the machine doesn't implement wakeup then we >> never reset the system at all. >> >> Shouldn't qemu_system_wakeup() do a qemu_devices_reset() >> if there's no MachineClass::wakeup, in a similar way to >> how qemu_system_reset() does a qemu_devices_reset() >> if there's no MachineClass::reset method ? Having the >> wakeup event be "sometimes this will do a RESET_TYPE_WAKEUP >> but sometimes it won't" doesn't seem right to me... One thing one could consider would probably be to send a WARM reset to all devices. The main issue here is that other devices will default to a COLD device then, and that's precisely what the other machines that implement suspend+resume do not want. And ... > > From my understanding that I have gathered from the code (but please, > someone correct me if I am wrong), this is machine specific. Some > machine types might not support suspend+wake-up at all. The support > has to be explicitly advertised through qemu_register_wakeup_support() > (for example, aarch64 with a generic virt machine type does not > advertise support). Even if the machine type advertises > suspend+wake-up support, it might not need to do anything machine > specific. This is the case of pSeries PowerPC machine (sPAPR) that > advertises support, but does not implement MachineClass::wakeup() > method as nothing needs to change in the machine state. [1] > > So, if a restart during wake-up happens, it can be differentiated with > the wake-up reset type, and if the machine type does not need to reset > its devices during wake-up, there is no reset that needs to be > differentiated. ... if the machine does not do any resets during suspend+wakeup, this implies that there is not even a warm reset. I guess we should make that clearer in the documentation: it's up to a machine implementation whether it wants to trigger a WARM reset during suspend+wakeup. If not, not resets will be performed at all. @Peter, does that sound reasonable? -- Cheers, David / dhildenb