Re: [Libguestfs] [PATCH v2v 0/5] convert: Find out if Windows guest is expecting BIOS localtime or UTC
On Mon, Sep 25, 2023 at 5:19 PM Daniel P. Berrangé wrote: > On Mon, Sep 25, 2023 at 04:26:59PM +0200, Alice Frosi wrote: > > Hi Rich, > > > > On Mon, Sep 25, 2023 at 4:10 PM Richard W.M. Jones > > wrote: > > > > > [Alice: See patch 2] > > > > > > > I'm not 100% sure about the source of this work. However, we had in > > KubeVirt people interested in using localtime with Windows [1]. Yes, I > see > > that you pointed to that PR in patch 2. The problem with that PR is the > > migration. What happens if we migrate the VM to a host that is in another > > timezone? Is it going to break the application running inside the VM? > > I would generally expect all hosts to be configured in the same timezone, > for any given single cloud deployment. > > If you really are concerned about this problem though, libvirt lets you > set this explicitly eg > > > > I don't think we support this option in KubeVirt yet. It might be useful to extend it. However, I'm not sure if it is the user's responsibility to choose the TZ or if it should be decided by KubeVirt and not exposed to the API. Generally, I don't think we can always assume that all the node in the cluster are in the same time zone. This could be signaled with some labels and allow the VM to be scheduled only on the node with that label. > 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 :| > > ___ Libguestfs mailing list Libguestfs@redhat.com https://listman.redhat.com/mailman/listinfo/libguestfs
Re: [Libguestfs] [PATCH v2v 0/5] convert: Find out if Windows guest is expecting BIOS localtime or UTC
On Mon, Sep 25, 2023 at 05:49:18PM +0200, Laszlo Ersek wrote: > On 9/25/23 17:48, Laszlo Ersek wrote: > > On 9/25/23 16:04, Richard W.M. Jones wrote: > >> [Alice: See patch 2] > >> > >> [This patch is a bit rough, it could do with better commit messages > >> and some tests. Please test it to see if it solves the Windows > >> conversion issue described in the thread below.] > >> > >> We currently do not set any field in guest output. Most > >> Windows guests expect the BIOS to be set to localtime, whereas almost > >> all Linux guests would expect it to be set to UTC. It is also > >> possible to configure a Windows guest to expect BIOS set to UTC. > >> > >> The default is usually BIOS set to UTC, so for many Windows guests > >> this would be wrong. This specifically may cause problems when > >> scheduling qemu-ga installation, see the thread here: > >> > >> https://listman.redhat.com/archives/libguestfs/2023-September/thread.html#32556 > >> > >> but could cause other general issues with time in the guest. > >> > >> One way to implement this would be to copy the source hypervisor > >> information across; however I'm not confident this information is read > >> correctly. A better way is to read out what the guest is expecting > >> from the Windows registry. (For Linux we just assume BIOS is always > >> UTC, since that's the default for almost any Linux guest which hasn't > >> been dual-booted with Windows, which for VMs would be incredibly > >> rare.) > > > > I think the word "BIOS" is incorrectly used all over the series; I'd > > rather say "RTC" / "real time clock". > > ... meaning patch subject lines, commit message bodies, and code. OK :-) Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com libguestfs lets you edit virtual machines. Supports shell scripting, bindings from many languages. http://libguestfs.org ___ Libguestfs mailing list Libguestfs@redhat.com https://listman.redhat.com/mailman/listinfo/libguestfs
Re: [Libguestfs] [PATCH v2v 0/5] convert: Find out if Windows guest is expecting BIOS localtime or UTC
On 9/25/23 17:48, Laszlo Ersek wrote: > On 9/25/23 16:04, Richard W.M. Jones wrote: >> [Alice: See patch 2] >> >> [This patch is a bit rough, it could do with better commit messages >> and some tests. Please test it to see if it solves the Windows >> conversion issue described in the thread below.] >> >> We currently do not set any field in guest output. Most >> Windows guests expect the BIOS to be set to localtime, whereas almost >> all Linux guests would expect it to be set to UTC. It is also >> possible to configure a Windows guest to expect BIOS set to UTC. >> >> The default is usually BIOS set to UTC, so for many Windows guests >> this would be wrong. This specifically may cause problems when >> scheduling qemu-ga installation, see the thread here: >> >> https://listman.redhat.com/archives/libguestfs/2023-September/thread.html#32556 >> >> but could cause other general issues with time in the guest. >> >> One way to implement this would be to copy the source hypervisor >> information across; however I'm not confident this information is read >> correctly. A better way is to read out what the guest is expecting >> from the Windows registry. (For Linux we just assume BIOS is always >> UTC, since that's the default for almost any Linux guest which hasn't >> been dual-booted with Windows, which for VMs would be incredibly >> rare.) > > I think the word "BIOS" is incorrectly used all over the series; I'd > rather say "RTC" / "real time clock". ... meaning patch subject lines, commit message bodies, and code. ___ Libguestfs mailing list Libguestfs@redhat.com https://listman.redhat.com/mailman/listinfo/libguestfs
Re: [Libguestfs] [PATCH v2v 0/5] convert: Find out if Windows guest is expecting BIOS localtime or UTC
On 9/25/23 16:04, Richard W.M. Jones wrote: > [Alice: See patch 2] > > [This patch is a bit rough, it could do with better commit messages > and some tests. Please test it to see if it solves the Windows > conversion issue described in the thread below.] > > We currently do not set any field in guest output. Most > Windows guests expect the BIOS to be set to localtime, whereas almost > all Linux guests would expect it to be set to UTC. It is also > possible to configure a Windows guest to expect BIOS set to UTC. > > The default is usually BIOS set to UTC, so for many Windows guests > this would be wrong. This specifically may cause problems when > scheduling qemu-ga installation, see the thread here: > > https://listman.redhat.com/archives/libguestfs/2023-September/thread.html#32556 > > but could cause other general issues with time in the guest. > > One way to implement this would be to copy the source hypervisor > information across; however I'm not confident this information is read > correctly. A better way is to read out what the guest is expecting > from the Windows registry. (For Linux we just assume BIOS is always > UTC, since that's the default for almost any Linux guest which hasn't > been dual-booted with Windows, which for VMs would be incredibly > rare.) I think the word "BIOS" is incorrectly used all over the series; I'd rather say "RTC" / "real time clock". Laszlo ___ Libguestfs mailing list Libguestfs@redhat.com https://listman.redhat.com/mailman/listinfo/libguestfs
Re: [Libguestfs] [PATCH v2v 0/5] convert: Find out if Windows guest is expecting BIOS localtime or UTC
On Mon, Sep 25, 2023 at 04:26:59PM +0200, Alice Frosi wrote: > Hi Rich, > > On Mon, Sep 25, 2023 at 4:10 PM Richard W.M. Jones > wrote: > > > [Alice: See patch 2] > > > > I'm not 100% sure about the source of this work. However, we had in > KubeVirt people interested in using localtime with Windows [1]. Yes, I see > that you pointed to that PR in patch 2. The problem with that PR is the > migration. What happens if we migrate the VM to a host that is in another > timezone? Is it going to break the application running inside the VM? I would generally expect all hosts to be configured in the same timezone, for any given single cloud deployment. If you really are concerned about this problem though, libvirt lets you set this explicitly eg 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 :| ___ Libguestfs mailing list Libguestfs@redhat.com https://listman.redhat.com/mailman/listinfo/libguestfs
Re: [Libguestfs] [PATCH v2v 0/5] convert: Find out if Windows guest is expecting BIOS localtime or UTC
Hi Rich, On Mon, Sep 25, 2023 at 4:10 PM Richard W.M. Jones wrote: > [Alice: See patch 2] > I'm not 100% sure about the source of this work. However, we had in KubeVirt people interested in using localtime with Windows [1]. Yes, I see that you pointed to that PR in patch 2. The problem with that PR is the migration. What happens if we migrate the VM to a host that is in another timezone? Is it going to break the application running inside the VM? IMO, that was the major blocker of that PR. I initially suggested that we either avoid migration as a first step or try to migrate only on nodes at the same timezone, Do you know if anyone has experience on this particular problem? [1] https://github.com/kubevirt/kubevirt/pull/9587 Many thanks, Alice ___ Libguestfs mailing list Libguestfs@redhat.com https://listman.redhat.com/mailman/listinfo/libguestfs
Re: [Libguestfs] [PATCH v2v 0/5] convert: Find out if Windows guest is expecting BIOS localtime or UTC
On Mon, Sep 25, 2023 at 04:26:59PM +0200, Alice Frosi wrote: > Hi Rich, > > On Mon, Sep 25, 2023 at 4:10 PM Richard W.M. Jones wrote: > > [Alice: See patch 2] > > > I'm not 100% sure about the source of this work. However, we had in > KubeVirt people interested in using localtime with Windows [1]. Yes, > I see that you pointed to that PR in patch 2. The problem with that > PR is the migration. What happens if we migrate the VM to a host > that is in another timezone? Is it going to break the application > running inside the VM? Does every Windows VM running in Kubevirt have its registry adjusted so it expects the BIOS to be set to UTC? (ie: https://wiki.archlinux.org/title/System_time#UTC_in_Microsoft_Windows). This is a non-standard setting, but I can't understand how Windows VMs would have correct clocks if this were not the case. BTW you could find out by running: $ virt-win-reg window.img 'HKLM\SYSTEM' on some Kubevirt Windows VMs, and looking for: [\ControlSet001\Control\TimeZoneInformation] in the output. See if there is a key called "RealTimeIsUniversal" and what it is set to. If it is the case that this is always set for existing Kubevirt guests, then virt-v2v would have to be changed so it also sets this registry entry when the output is Kubevirt. I agree that migration across timezones is highly problematic for the BIOS = localtime situation. I don't see any solution for that except disallowing it. > IMO, that was the major blocker of that PR. I initially suggested that we > either avoid migration as a first step or try to migrate only on nodes at the > same timezone, > Do you know if anyone has experience on this particular problem? I guess RHV must have encountered this before, but I don't know any specifics. Thanks, Rich. > [1] https://github.com/kubevirt/kubevirt/pull/9587 > > Many thanks, > Alice -- 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 ___ Libguestfs mailing list Libguestfs@redhat.com https://listman.redhat.com/mailman/listinfo/libguestfs
[Libguestfs] [PATCH v2v 0/5] convert: Find out if Windows guest is expecting BIOS localtime or UTC
[Alice: See patch 2] [This patch is a bit rough, it could do with better commit messages and some tests. Please test it to see if it solves the Windows conversion issue described in the thread below.] We currently do not set any field in guest output. Most Windows guests expect the BIOS to be set to localtime, whereas almost all Linux guests would expect it to be set to UTC. It is also possible to configure a Windows guest to expect BIOS set to UTC. The default is usually BIOS set to UTC, so for many Windows guests this would be wrong. This specifically may cause problems when scheduling qemu-ga installation, see the thread here: https://listman.redhat.com/archives/libguestfs/2023-September/thread.html#32556 but could cause other general issues with time in the guest. One way to implement this would be to copy the source hypervisor information across; however I'm not confident this information is read correctly. A better way is to read out what the guest is expecting from the Windows registry. (For Linux we just assume BIOS is always UTC, since that's the default for almost any Linux guest which hasn't been dual-booted with Windows, which for VMs would be incredibly rare.) Rich. ___ Libguestfs mailing list Libguestfs@redhat.com https://listman.redhat.com/mailman/listinfo/libguestfs
