On Thu, Feb 09, 2023 at 01:54:42PM +0000, Daniel P. Berrangé wrote:
On Thu, Feb 09, 2023 at 01:45:33PM +0000, Richard W.M. Jones wrote:
> This machine type is more modern than the older 'pc' type and as most
> qemu development is now focused there we expect it will perform and
> behave better. In almost all respects this change should make no
> difference.
The key differences with q35 that have caused problems for
apps in the past
- CDROMs must use 'sata' bus not 'ide'
- PCI topology is completely different, so if you're
trying to associate between the host side view of
the config and the guest side view, your logic may
need adapting
- Hotplug of devices is limited to 1 device unless you
pre-create a bunch of pcie-root-port devices
If you're already using 'virt' machine for aarch64 successfully
though, you should have already known about the last 2 points,
if they did indeed affect libguestfs.
The first point could conceivably affect the way to detect
devices, depending on what approach is used, but could equally
be a non issue.
I presume the libguestfs test suite would have complained if
there was any genuine problem with the change, since it is
pretty comphrensive.
I ran the full test suite and there were no complaints. In particular
we do now do some complicated mapping between PCI and our internal
device names[1] and at least the test of that didn't complain.
I suspect we could see problems in guestfs-tools, especially things
like virt-customize which are running things inside the appliance.
For RHEL I have scheduled this change for early in the 9.3 cycle so
there is plenty of time to test it.
Rich.
[1]
https://github.com/libguestfs/libguestfs/blob/master/daemon/device-name-t...
>
> Fixes:
https://bugzilla.redhat.com/show_bug.cgi?id=2168578
> ---
> lib/guestfs-internal.h | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/lib/guestfs-internal.h b/lib/guestfs-internal.h
> index 07a2b9f617..4e9a103d78 100644
> --- a/lib/guestfs-internal.h
> +++ b/lib/guestfs-internal.h
> @@ -128,6 +128,9 @@ cleanup_mutex_unlock (pthread_mutex_t **ptr)
> #define MAX_WINDOWS_EXPLORER_SIZE (4 * 1000 * 1000)
>
> /* Machine types. */
> +#if defined(__x86_64__)
> +#define MACHINE_TYPE "q35"
> +#endif
> #ifdef __arm__
> #define MACHINE_TYPE "virt"
> #endif
> --
> 2.39.0
>
> _______________________________________________
> Libguestfs mailing list
> Libguestfs(a)redhat.com
>
https://listman.redhat.com/mailman/listinfo/libguestfs
>
With regards,
Daniel
--
|:
https://berrange.com -o-
https://www.flickr.com/photos/dberrange :|
|:
https://libvirt.org -o-
https://fstop138.berrange.com :|
|:
https://entangle-photo.org -o-
https://www.instagram.com/dberrange :|
--
Richard Jones, Virtualization Group, Red Hat
http://people.redhat.com/~rjones
Read my programming and virtualization blog:
http://rwmj.wordpress.com
virt-top is 'top' for virtual machines. Tiny program with many
powerful monitoring features, net stats, disk stats, logging, etc.
http://people.redhat.com/~rjones/virt-top