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 lists1p.gnu.org (lists1p.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 4F74BF9D0EB for ; Tue, 14 Apr 2026 17:57:46 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists1p.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1wCi0s-0000W2-GS; Tue, 14 Apr 2026 13:57:26 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists1p.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1wCi0q-0000VZ-SO for qemu-devel@nongnu.org; Tue, 14 Apr 2026 13:57:24 -0400 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 1wCi0p-0007ts-0K for qemu-devel@nongnu.org; Tue, 14 Apr 2026 13:57:24 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1776189440; 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: in-reply-to:in-reply-to:references:references; bh=+vzaEKabxdv0/3CjORshcJXEpntjnx8/hX1P+eHVG7A=; b=Fkp/pHsO+qjtZpMJgCvXBWyAzyevCbpZ8KMmqaTaomrrzlO8a4GjgHekdkB4n8Bf4MH8U9 GxRepRxgXQ5FhE01RVJ7SL9v7TfSoEysGQ5R6fP7Tf3Xh9Q1Nlf6xH5rNiWaiaw5aP1UZR wee1s9wazsdyuJt3bVUSe2q0IWfagvE= Received: from mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-114-dPsxRGMFM_CbTN7NoCmzKA-1; Tue, 14 Apr 2026 13:57:17 -0400 X-MC-Unique: dPsxRGMFM_CbTN7NoCmzKA-1 X-Mimecast-MFC-AGG-ID: dPsxRGMFM_CbTN7NoCmzKA_1776189435 Received: from mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.17]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 7BAE5180034E; Tue, 14 Apr 2026 17:57:14 +0000 (UTC) Received: from localhost (unknown [10.44.50.237]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 3E72D195608E; Tue, 14 Apr 2026 17:57:12 +0000 (UTC) Date: Tue, 14 Apr 2026 13:57:10 -0400 From: Stefan Hajnoczi To: mr-083 Cc: qemu-devel@nongnu.org, qemu-block@nongnu.org, its@irrelevant.dk, kbusch@kernel.org, mr-083 , kwolf@redhat.com Subject: Re: [PATCH 2/2] block/monitor: add drive_insert HMP command Message-ID: <20260414175710.GA136064@fedora> References: <20260409060155.94704-1-matthieu@min.io> <20260409060155.94704-3-matthieu@min.io> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="CPETiYvycK+BqAR0" Content-Disposition: inline In-Reply-To: <20260409060155.94704-3-matthieu@min.io> X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 Received-SPF: pass client-ip=170.10.133.124; envelope-from=stefanha@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -25 X-Spam_score: -2.6 X-Spam_bar: -- X-Spam_report: (-2.6 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.54, 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=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_PASS=-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: qemu development 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 --CPETiYvycK+BqAR0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Thu, Apr 09, 2026 at 08:01:54AM +0200, mr-083 wrote: > Add a drive_insert HMP command that reconnects a host block device file > to an existing guest device whose backing store was previously removed > with drive_del. >=20 > After drive_del, the BlockBackend remains attached to the guest device > but has no BlockDriverState (shown as "[not inserted]" in info block). > drive_insert opens the specified file, finds the device's BlockBackend > by iterating all backends and matching the attached device ID, then > calls blk_insert_bs() to reconnect the backing store. >=20 > This complements drive_del for non-removable devices (such as NVMe > namespaces) where blockdev-change-medium cannot be used. Combined with > PCIe AER Surprise Down error injection to trigger a controller reset, > this enables complete NVMe disk hot-swap simulation where the guest > sees the same device names throughout. >=20 > Example usage: > drive_del drv0 # remove backing store > drive_insert ns0 disk.qcow2 # reconnect backing > pcie_aer_inject_error rp0 SDN # trigger controller reset This approach does not delete the `--device nvme-ns` but instead replaces the BlockBackend's root node so that the existing NVMe Namespace changes the underlying storage. Questions about this approach: 1. NVMe AEN is not involved at all? 2. Does the guest have access to the new storage as soon as drive_insert completes and the PCIe AER is just to kick the guest driver (e.g. getting it to update the size of the guest Linux block device)? Stefan --CPETiYvycK+BqAR0 Content-Type: application/pgp-signature; name=signature.asc -----BEGIN PGP SIGNATURE----- iQEzBAEBCgAdFiEEhpWov9P5fNqsNXdanKSrs4Grc8gFAmnef/YACgkQnKSrs4Gr c8gWXwgAyj+zrgRhWWvZUZZYK4vU81UPE6HSv0G7aDS8tJVhNRDdCPEyyp9iaiq6 MEs0jPgzBRv0cv+NhvyGsL9N83Se8zTsHOM4ul5Cr3ErpWxIkxcfroed2HPgiwsC 0+2dJBEmtwCyS+/geJOu9W33RmUSroD7w3M3A9vQ3uLmOmF6cObRumv+K7+OfBzd cprnRZMrJaPaZLCJ0AfKNqaq4gAHrFwU2SAPkc/W4XT8nWEoqBZG/0ZvAxxJDSFo HXC0dgxlzSSfp1LB5jtw5In2RaSgOjkYxFh8kRcW8MA0jf3DMgEsdXaNheuZKBgq VVddJVVKphjP566OJr98BMx0QfxyaA== =dmz4 -----END PGP SIGNATURE----- --CPETiYvycK+BqAR0--