Re: [Xen-devel] Radical proposal: ship not-fully-tidied shim as 4.10.1

[Hans van Kranenburg <hans@xxxxxxxxxxx>]

On 01/09/2018 07:22 PM, Rich Persaud wrote:
>>> On Jan 9, 2018, at 12:56, Stefano Stabellini <sstabellini@xxxxxxxxxx> wrote:
>>>
>>> On Tue, 9 Jan 2018, Doug Goldstein wrote:
>>> On 1/9/18 11:33 AM, Jan Beulich wrote:
>>>>>>> On 09.01.18 at 18:23, <anthony@xxxxxxxxxxxxx> wrote:
>>>>> On Tue, Jan 9, 2018 at 8:52 AM, Stefano Stabellini
>>>>> <sstabellini@xxxxxxxxxx> wrote:
>>>>>>>> On Tue, 9 Jan 2018, George Dunlap wrote:
>>>>>>>> On Mon, Jan 8, 2018 at 9:01 PM, Rich Persaud <persaur@xxxxxxxxx> wrote:
>>>>>>>> On a similarly pragmatic note: would a variation of Anthony's vixen 
>>>>>>>> patch
>>>>> series be suitable for pre-PVH Xen 4.6 - 4.9?  These versions are 
>>>>> currently 
>>>>> documented as security-supported (Oct 2018 - July 2020).
>>>>>>>
>>>>>>> Hmm, Ian's mail seems to be focusing on the idea of checking in a
>>>>>>> non-polished series to 4.10, rather than exctly what the content of
>>>>>>> that series would be.
>>>>>>>
>>>>>>> In the IRL conversation that preceeded this mail, the new short-term
>>>>>>> target we discussed was:
>>>>>>> 1. A 4.10-based shim that could boot either under HVM or PVH
>>>>>>> 2. A script that would take an existing PV config, and spit out a) a
>>>>>>> bootable ISO with the shim & whatever was needed, and b) a new config
>>>>>>> that would boot the same VM, but in HVM mode with the shim
>>>>>>>
>>>>>>> The script + a 4.10 shim binary *should* allow most PV guests to boot
>>>>>>> without any changes whatsoever for most older versions of Xen.
>>>>>>>
>>>>>>> There are a number of people for whom this won't work; I think we also
>>>>>>> need to provide a way to transparently change PV guests into PVshim
>>>>>>> guests.  But that will necessarily involve significant toolstack
>>>>>>> functionality, at which point you might as well backport PVH as well.
>>>>>>
>>>>>> Yes, there will be a number of people that won't be covered by this fix,
>>>>>> including those that can't use HVM/PVH mode because VT-x isn't available
>>>>>> at all in their environment. That is the only reason to run PV today.
>>>>>> Providing a way to transparently change PV guests into PVshim guests
>>>>>> won't cover any of these cases. A more complete workaround to SP3 is
>>>>>> along the lines of https://marc.info/?l=xen-devel&m=151509740625690.
>>>>>>
>>>>>> That said, I realize that we are only trying to do the best we can in a
>>>>>> very difficult situation, with very little time in our hands. I agree
>>>>>> with Ian that we should commit something unpolished and only partially
>>>>>> reviewed soon, even though it doesn't cover a good chunk of the userbase
>>>>>> for one reason or another. Even if migration doesn't work, it will still
>>>>>> help all that don't require it. It is only a partial fix by nature
>>>>>> anyway.
>>>>>
>>>>> Can people be a bit more explicit about what they think should be done 
>>>>> here?
>>>>>
>>>>> I'm happy to redirect effort to PVH shim if that's what the solution
>>>>> is going to be.
>>>>>
>>>>> I obviously prefer the HVM approach as it works on a broad range of Xen 
>>>>> versions
>>>>> without modification but I'm keen to get something done quickly and
>>>>> don't want to
>>>>> waste effort.
>>>>
>>>> From what I've read today, I have no reason to believe the PVH
>>>> shim won't work in HVM mode. How would the HVM-only approach
>>>> be better in that case?
>>>>
>>>> Jan
>>>
>>> I feel like I should state the obvious here. Its tested over a large
>>> data set.
>>
>> Right: if we are going to commit something unpolished and unreviewed,
>> let it be at least very well tested by the submitter. Honest question:
>> how much more dev&test we need on PVShim before we get it to similar
>> levels of confidence?
> 

> Since the primary audience for security fixes are production
> deployments of Xen where customer assets are at risk, is there an
> estimate for the percentage/size of Xen deployments where PVH (not
> only Xen 4.10) has already been deployed for production customers?
> That could give other customers more confidence in deploying PVH in
> production.
+1

I have been hearing mostly-very-positive stories around, except for the
missing pvgrub2 support. :)

But as a sysadmin who's also strongly considering to jump to 4.10 and
PVH I'd definitely like to hear more stories.

Hans

Hans

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