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[2a10:fc81:a806:d6a9::1]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-438bd54bfa5sm35332425e9.25.2025.01.24.10.57.27 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 24 Jan 2025 10:57:28 -0800 (PST) Date: Fri, 24 Jan 2025 19:57:24 +0100 From: Stefano Brivio To: Laurent Vivier Subject: Re: [PATCH] vhost-user: Implement an empty VHOST_USER_SEND_RARP command Message-ID: <20250124195724.30ef0099@elisabeth> In-Reply-To: References: <20250124142137.2296704-1-lvivier@redhat.com> <20250124171016.322d665b@elisabeth> <5af65c6f-3bab-4852-84ac-ca8f23123b2e@redhat.com> <20250124194016.4c26375c@elisabeth> Organization: Red Hat X-Mailer: Claws Mail 4.2.0 (GTK 3.24.41; x86_64-pc-linux-gnu) MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: 8uyxmZCVNiUhkMzJx115CY9hOVWrgjOKZjHQ_AJzx18_1737745051 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Message-ID-Hash: ITCML2GNQOQOJQOSJUZHCJ6VG3BGE2OM X-Message-ID-Hash: ITCML2GNQOQOJQOSJUZHCJ6VG3BGE2OM X-MailFrom: sbrivio@redhat.com X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; emergency; loop; banned-address; member-moderation; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header CC: passt-dev@passt.top X-Mailman-Version: 3.3.8 Precedence: list List-Id: Development discussion and patches for passt Archived-At: Archived-At: List-Archive: List-Archive: List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: On Fri, 24 Jan 2025 19:50:57 +0100 Laurent Vivier wrote: > On 24/01/2025 19:40, Stefano Brivio wrote: > > On Fri, 24 Jan 2025 19:35:33 +0100 > > Laurent Vivier wrote: > > > >> On 24/01/2025 17:10, Stefano Brivio wrote: > >>> On Fri, 24 Jan 2025 15:21:37 +0100 > >>> Laurent Vivier wrote: > >>> > >>>> Passt cannot manage and doesn't need to manage the broadcast of a fake RARP, > >>>> but QEMU will report an error message if Passt doesn't implement it. > >>>> > >>>> Implement an empty SEND_RARP command to silence QEMU error message. > >>>> > >>>> Signed-off-by: Laurent Vivier > >>>> --- > >>>> vhost_user.c | 28 +++++++++++++++++++++++++++- > >>>> 1 file changed, 27 insertions(+), 1 deletion(-) > >>>> > >>>> diff --git a/vhost_user.c b/vhost_user.c > >>>> index f12dec5ddc58..e6633ae75ce8 100644 > >>>> --- a/vhost_user.c > >>>> +++ b/vhost_user.c > >>>> @@ -914,7 +914,8 @@ static bool vu_get_protocol_features_exec(struct vu_dev *vdev, > >>>> { > >>>> uint64_t features = 1ULL << VHOST_USER_PROTOCOL_F_REPLY_ACK | > >>>> 1ULL << VHOST_USER_PROTOCOL_F_LOG_SHMFD | > >>>> - 1ULL << VHOST_USER_PROTOCOL_F_DEVICE_STATE; > >>>> + 1ULL << VHOST_USER_PROTOCOL_F_DEVICE_STATE | > >>>> + 1ULL << VHOST_USER_PROTOCOL_F_RARP; > >>>> > >>>> (void)vdev; > >>>> vmsg_set_reply_u64(msg, features); > >>>> @@ -981,6 +982,30 @@ static bool vu_set_vring_enable_exec(struct vu_dev *vdev, > >>>> return false; > >>>> } > >>>> > >>>> +/** > >>>> + * vu_set_send_rarp_exec() - Broadcast a fake RARP to notify the migration > >>>> + * is terminated > >>> > >>> Fine, so we need to add this. > >>> > >>> But can we at least make it clear for our future benefit? That is, > >>> there's no such thing as "fake RARP". The only thing that's actually > >>> fake here is this callback. For others, see thread at: > >>> > >>> https://lore.kernel.org/qemu-devel/20250121100029.1106973-1-lvivier@redhat.com/ > >>> > >>> What about "Do nothing to silence QEMU bogus error message"? Claiming > >>> we are broadcasting a RARP message and not doing it is... confusing. > >> > >> I think it's interesting to have this comment as it comes from the vhost-user > >> specification as it describes the aim of the command, and we can add something like "but > >> as passt don't need to update any ARP table we do nothing only to silence QEMU bogus error > >> message". > > > > Eh, if we're already making it verbose, maybe we can go with something > > like: > > > > vhost-user specification says: "Broadcast ...", but passt ... > > As you prefer... > > If you want you can update the patch when you commit it. Given it's already two edits it would save me some time if you could write/format it properly... -- Stefano