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Mon, 25 Oct 2021 09:30:31 +0000 (UTC) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id DBF681377E; Mon, 25 Oct 2021 09:30:30 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id l0O2MjZ5dmHLTAAAMHmgww (envelope-from ); Mon, 25 Oct 2021 09:30:30 +0000 X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" X-Inumbo-ID: 2d62b5d0-1457-4fb0-b499-53ec4f4bc807 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1635154231; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=KRGww6yZbI/Yt5jVmhMhFsKU1wRB0IaHQ8wTV+diPmc=; b=BUpWf7a6s/iFTUKqBZ0IABlQlxTbqRFhhvFbzSJW9eK5MeTIMPQv04R3Vs/9eSP8RQwZo6 0P9Ys4O0nSz/xZc+CveKTXhCpBJGoRjxVS87pIhwU/fhwNbC2kdxUKw7Nix2ZsaE252nlg 14bqeEgsyrlUQYpvTSd3WP5jEe2p84Q= To: Andrew Cooper , xen-devel@lists.xenproject.org, linux-input@vger.kernel.org, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-fbdev@vger.kernel.org Cc: Dmitry Torokhov , Boris Ostrovsky , Stefano Stabellini References: <20211022064800.14978-1-jgross@suse.com> <20211022064800.14978-2-jgross@suse.com> From: Juergen Gross Subject: Re: [PATCH 1/5] xen: add "not_essential" flag to struct xenbus_driver Message-ID: <06bf785a-c661-ce18-6e48-7077c5944890@suse.com> Date: Mon, 25 Oct 2021 11:30:30 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.12.0 MIME-Version: 1.0 In-Reply-To: Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="osso5FxvKknFWuti2qByayI8n0rKWIOdo" This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --osso5FxvKknFWuti2qByayI8n0rKWIOdo Content-Type: multipart/mixed; boundary="UqKrfN4EOpH1zBdeQbsH4TMElHBbnARpK"; protected-headers="v1" From: Juergen Gross To: Andrew Cooper , xen-devel@lists.xenproject.org, linux-input@vger.kernel.org, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-fbdev@vger.kernel.org Cc: Dmitry Torokhov , Boris Ostrovsky , Stefano Stabellini Message-ID: <06bf785a-c661-ce18-6e48-7077c5944890@suse.com> Subject: Re: [PATCH 1/5] xen: add "not_essential" flag to struct xenbus_driver References: <20211022064800.14978-1-jgross@suse.com> <20211022064800.14978-2-jgross@suse.com> In-Reply-To: --UqKrfN4EOpH1zBdeQbsH4TMElHBbnARpK Content-Type: multipart/mixed; boundary="------------C02A3EE7C04771EB3B004689" Content-Language: en-US This is a multi-part message in MIME format. --------------C02A3EE7C04771EB3B004689 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: quoted-printable On 22.10.21 11:28, Andrew Cooper wrote: > On 22/10/2021 07:47, Juergen Gross wrote: >> When booting the xenbus driver will wait for PV devices to have >> connected to their backends before continuing. The timeout is differen= t >> between essential and non-essential devices. >> >> Non-essential devices are identified by their nodenames directly in th= e >> xenbus driver, which requires to update this list in case a new device= >> type being non-essential is added (this was missed for several types >> in the past). >> >> In order to avoid this problem, add a "not_essential" flag to struct >> xenbus_driver which can be set to "true" by the respective frontend. >> >> Set this flag for the frontends currently regarded to be not essential= >> (vkbs and vfb) and use it for testing in the xenbus driver. >> >> Signed-off-by: Juergen Gross >=20 > Wouldn't it be better to annotate essential?=C2=A0 That way, when new m= isc > drivers come along, they don't by default block boot. It isn't as if new drivers would "block boot". Normally the short timeout for all drivers of 30 seconds is more than enough for all of them. I'm a little bit hesitant to have a kind of "white listing" essential drivers, as there might be different views which drivers should have that flag. Doing this the other way round is easier: in case of disagreement such a patch just wouldn't go in, not breaking anything in that case. Additionally there might be out-of-tree PV drivers, which could be hit by not being flagged to be essential. With the not_essential flag the situation wouldn't change for such a driver. 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