Re: [Xen-users] Apply venom patch without rebooting guests

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

On Wed, 2015-06-03 at 07:01 +0530, Linux Hack wrote:
> Hi,
> 
> 
> I plan to apply venom patch using below method on dom0's which will
> avoid downtime for guests.
> 
> 
> * Migrate all the VM's to another dom0 where I have space
> * Apply venom patch on source dom0 and reboot the Dom0
> * once its up will migrate back the vm's to old dom0 itself. 
> 
> 
> But my concern is if i am doing by the above plan will newly applied
> xen related patch will be applied for the drivers whatever loaded on
> guests? 

XSA-133 / CVE-2015-3456 (I don't think using the marketing name is
useful, see also [0]) was a qemu issue, so even just a local host
migration (after having updated the qemu binary) should be sufficient
since the DM is restarted on the other end of a migration.

Of course migrating away and rebooting the dom0 would make 100% sure you
hadn't accidentally missed a VM. (I suppose looking at /prod/*/exe could
help too, since you'd see the old binary)

> Also is there way to get hypervisior details from guest vm?

Depends on the guest, Linux puts some stuff in /sys/.../hypervisor IIRC,
and there is some stuff in dmesg on boot. Note that the qemu version
isn't one of the things you'll see there.

Ian.

[0] http://backronym.fail/



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