Re: [PATCH] libvirt: update default extra storage drive

[Luis Chamberlain <mcgrof@kernel.org>]

On Tue, May 06, 2025 at 11:18:28AM +0200, Daniel Gomez wrote:
> From: Daniel Gomez <da.gomez@samsung.com>
> 
> kdevops expects NVMe to be selected as stated in the config.

In which config?

> However,
> virtio is the default. Change the default to match the expectation in
> the default case.

So, the history here was that through experience on a lot of testing
(specially the stable folks) they experienced *tons* of NVMe timeouts
as flaky failure tests. Part of this was root caused to the slow
performant qemu NVMe driver since it lacked using qemu IO threads, which
allows the device to perform I/O in its own thread rather than in the
main QEMU thread. Virtio already has support IO threads, so as soon as we
switched to virtio that fixed the issues.

Yes, it would be good to make NVMe the default backend storage driver
but if default qemu release on distros don't yet have IO thread support
then it makes no sense to switch over, sadly.

Klaus, what's the state of affairs for this?

 Luis

> Signed-off-by: Daniel Gomez <da.gomez@samsung.com>
> ---
>  kconfigs/Kconfig.libvirt | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kconfigs/Kconfig.libvirt b/kconfigs/Kconfig.libvirt
> index 8654eb9b1a0607222ffb6749ed5b4b5f68c912f6..424a515d2fb1ad4edeacec14e4fe49e110b88b7b 100644
> --- a/kconfigs/Kconfig.libvirt
> +++ b/kconfigs/Kconfig.libvirt
> @@ -526,7 +526,7 @@ config LIBVIRT_HOST_PASSTHROUGH
>  
>  choice
>  	prompt "Libvirt extra storage driver to use"
> -	default LIBVIRT_EXTRA_STORAGE_DRIVE_VIRTIO
> +	default LIBVIRT_EXTRA_STORAGE_DRIVE_NVME
>  
>  config LIBVIRT_EXTRA_STORAGE_DRIVE_NVME
>  	bool "NVMe"

While