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From: Fiona Ebner <f.ebner@proxmox.com>
To: "Fabian Grünbichler" <f.gruenbichler@proxmox.com>,
	"Proxmox VE development discussion" <pve-devel@lists.proxmox.com>
Subject: Re: [pve-devel] [PATCH qemu-server 15/22] vm start/commandline: activate volumes before config_to_command()
Date: Mon, 16 Jun 2025 14:57:12 +0200	[thread overview]
Message-ID: <f415f46b-e6ed-40fe-a22c-bf3d67c6f5a4@proxmox.com> (raw)
In-Reply-To: <1780360255.3460.1750077980300@webmail.proxmox.com>

Am 16.06.25 um 14:46 schrieb Fabian Grünbichler:
>> Fiona Ebner <f.ebner@proxmox.com> hat am 16.06.2025 13:51 CEST geschrieben:
>> Am 16.06.25 um 13:31 schrieb DERUMIER, Alexandre via pve-devel:
>>>>> With '-blockdev', it is necessary to activate the volumes to generate
>>>>> the command line, because it can be necessary to check whether the
>>>>> volume is a block device or a regular file.
>>>
>>> I was thinking about that, but do we have storage with activate_volume
>>> need to be done for a regular file ?
>>>
>>> for lvm plugin for example, we could return always driver=>host_device.
>>>
>>> activate_volume is always done in specific plugin, so the plugin should
>>> be able to tell if it's a block or file storage
>>>
>>> only custom path passthrough in vm configuration need to be checked if
>>> it's a file or device, but we don't have activate_volume anyway
>>
>> Good point! It is needed for the default implementation of
>> qemu_blockdev_options() in Plugin.pm. We could go ahead and have all
>> plugins use their own implementation of qemu_blockdev_options(), that
>> would avoid doing any actual IO there. That sounds good to me.
>>
>> The downside is that it would break third-party plugins that would
>> otherwise work fine with the default implementation. But actually, it's
>> only those that need to do something in activate_volume() to make the
>> volume accessible. Maybe requiring those to provide their own
>> qemu_blockdev_options() implementation is an acceptable level of
>> breakage, not entirely sure. We could even try and just guess in the
>> default implementation if we cannot access the volume, maybe based on
>> the presence of 'path'.
>>
>> @Fabian does that sound acceptable to you?
> 
> not sure I follow completely, to avoid misunderstandings:
> 
> variant A:
> 
> move activate_volume up front, no breakage, but more churn and higher 
> chance of leaving activated volumes around in case starting fails

It's not "no breakage". Plugins that are not happy with the default
implementation of qemu_blockdev_options() would still fail.

> variant B:
> 
> move decision which driver to use to plugin via qemu_blockdev_options

Yes.

> how would the default/fallback look like here? without activation, we
> can't rely on path since that doesn't currently require being activated,
> so we can't use it to distinguish block devices from files prior to
> activation..

As written above, we could still try to probe the file like we currently
do. If that works, great, we don't lose anything compared to variant A.
If that fails, we look at whether path is set. If yes, then assume it's
a file-based storage and use the 'file' driver. Otherwise, use the
'host_device' driver.


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  reply	other threads:[~2025-06-16 12:57 UTC|newest]

Thread overview: 62+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-06-12 14:02 [pve-devel] [PATCH-SERIES qemu-server 00/22] preparation for switch to blockdev Fiona Ebner
2025-06-12 14:02 ` [pve-devel] [PATCH qemu-server 01/22] drive: code cleanup: drop unused $vmid parameter from get_path_and_format() Fiona Ebner
2025-06-12 14:02 ` [pve-devel] [PATCH qemu-server 02/22] cfg2cmd: require at least QEMU binary version 6.0 Fiona Ebner
2025-06-13  9:18   ` Fabian Grünbichler
2025-06-16  8:47     ` Fiona Ebner
2025-06-12 14:02 ` [pve-devel] [PATCH qemu-server 03/22] drive: parse: use hash argument for optional parameters Fiona Ebner
2025-06-12 14:02 ` [pve-devel] [PATCH qemu-server 04/22] drive: parse drive: support parsing with additional properties Fiona Ebner
2025-06-12 14:02 ` [pve-devel] [PATCH qemu-server 05/22] restore: parse drive " Fiona Ebner
2025-06-13  9:30   ` Fabian Grünbichler
2025-06-16  8:51     ` Fiona Ebner
2025-06-12 14:02 ` [pve-devel] [PATCH qemu-server 06/22] drive: remove geometry options gone since QEMU 3.1 Fiona Ebner
2025-06-12 14:02 ` [pve-devel] [PATCH qemu-server 07/22] clone disk: io uring check: fix call to determine cache direct Fiona Ebner
2025-06-12 14:02 ` [pve-devel] [PATCH qemu-server 08/22] drive: move storage_allows_io_uring_default() and drive_uses_cache_direct() helpers to drive module Fiona Ebner
2025-06-12 14:02 ` [pve-devel] [PATCH qemu-server 09/22] drive: introduce aio_cmdline_option() helper Fiona Ebner
2025-06-12 14:02 ` [pve-devel] [PATCH qemu-server 10/22] drive: introduce detect_zeroes_cmdline_option() helper Fiona Ebner
2025-06-12 14:02 ` [pve-devel] [PATCH qemu-server 11/22] introduce StateFile module for state file related helpers Fiona Ebner
2025-06-12 14:02 ` [pve-devel] [PATCH qemu-server 12/22] vm start: move state file handling to dedicated module Fiona Ebner
2025-06-13 10:00   ` Fabian Grünbichler
2025-06-16 10:34     ` Fiona Ebner
2025-06-16 10:54       ` Fabian Grünbichler
2025-06-16 10:57         ` Fiona Ebner
2025-06-12 14:02 ` [pve-devel] [PATCH qemu-server 13/22] vm start: move config_to_command() call further down Fiona Ebner
2025-06-13 10:05   ` Fabian Grünbichler
2025-06-16 10:54     ` Fiona Ebner
2025-06-12 14:02 ` [pve-devel] [PATCH qemu-server 14/22] vm start/commandline: also clean up pci reservation when config_to_command() fails Fiona Ebner
2025-06-12 14:02 ` [pve-devel] [PATCH qemu-server 15/22] vm start/commandline: activate volumes before config_to_command() Fiona Ebner
2025-06-13 10:16   ` Fabian Grünbichler
2025-06-17  7:46     ` Fiona Ebner
2025-06-13 10:25   ` Fabian Grünbichler
2025-06-16 11:31   ` DERUMIER, Alexandre via pve-devel
2025-06-16 11:51     ` Fiona Ebner
2025-06-16 12:46       ` Fabian Grünbichler
2025-06-16 12:57         ` Fiona Ebner [this message]
2025-06-16 13:15           ` Fabian Grünbichler
2025-06-16 13:27             ` Fiona Ebner
     [not found]   ` <409e12ad0b53d1b51c30717e6b9df3d370112df4.camel@groupe-cyllene.com>
2025-06-17  6:04     ` DERUMIER, Alexandre via pve-devel
2025-06-17  7:35       ` Fiona Ebner
2025-06-12 14:02 ` [pve-devel] [PATCH qemu-server 16/22] print drive device: explicitly set write-cache starting with machine version 10.0 Fiona Ebner
2025-06-13 10:28   ` Fabian Grünbichler
2025-06-17  7:47     ` Fiona Ebner
2025-06-12 14:02 ` [pve-devel] [PATCH qemu-server 17/22] print drive device: set {r, w}error front-end properties " Fiona Ebner
2025-06-12 14:02 ` [pve-devel] [PATCH qemu-server 18/22] print drive device: don't reference any drive for 'none' " Fiona Ebner
2025-06-13 11:14   ` Fabian Grünbichler
2025-06-17  7:54     ` Fiona Ebner
2025-06-12 14:02 ` [pve-devel] [PATCH qemu-server 19/22] drive: create a throttle group for each drive " Fiona Ebner
2025-06-13 11:23   ` Fabian Grünbichler
2025-06-17  7:58     ` Fiona Ebner
2025-06-12 14:02 ` [pve-devel] [PATCH qemu-server 20/22] blockdev: add helpers to generate blockdev commandline Fiona Ebner
2025-06-13 11:35   ` Fabian Grünbichler
2025-06-17  9:37     ` Fiona Ebner
2025-06-17  9:58       ` Fabian Grünbichler
2025-06-16 11:07   ` DERUMIER, Alexandre via pve-devel
2025-06-17 10:02     ` Fiona Ebner
2025-06-12 14:02 ` [pve-devel] [RFC qemu-server 21/22] blockdev: add support for NBD paths Fiona Ebner
2025-06-16 10:46   ` DERUMIER, Alexandre via pve-devel
2025-06-17 10:11     ` Fiona Ebner
2025-06-12 14:02 ` [pve-devel] [RFC qemu-server 22/22] command line: switch to blockdev starting with machine version 10.0 Fiona Ebner
2025-06-16 10:40   ` DERUMIER, Alexandre via pve-devel
2025-06-18 11:39     ` Fiona Ebner
2025-06-18 12:04       ` DERUMIER, Alexandre via pve-devel
2025-06-16  6:22 ` [pve-devel] [PATCH-SERIES qemu-server 00/22] preparation for switch to blockdev DERUMIER, Alexandre via pve-devel
2025-06-16  8:44   ` Fiona Ebner

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