Re: [Xen-devel] PVH backports to 4.9 and 4.8

[George Dunlap <george.dunlap@xxxxxxxxxx>]

On 01/11/2018 10:58 AM, Roger Pau Monné wrote:
> On Tue, Jan 09, 2018 at 05:08:15PM +0000, George Dunlap wrote:
>> Part of our solution to XSA-254 SP3 (aka "Meltdown") is to backport
>> the PVH mode from 4.10 to 4.9 and 4.8.  This will first allow people
>> able to run PVH kernels to switch their PV guests directly to PVH
>> guests; and second, eventually enable the backport of patches which
>> will enable transparent changing of PV guests into PVH guests.
>>
>> All of the hypervisor support seems to have existed already in 4.8, so
>> the only backports involve toolstack patches.
> 
> Thanks for looking into this.
> 
> My general opinion given those are toolstack only patches is that if
> it works it's fine.
> 
>> I've put up two trees for a first-cut backport of the PVH
>> functionality, to 4.9 and 4.8 here:
>>
>> git://xenbits.xen.org/people/gdunlap/xen.git
>>
>> Branches out/pvh-backport/4.8/v1 and out/pvh-backport/4.9/v1
>>
>> Below are the patches backported from 4.10 to 4.9 (23 patches total):
>>
>> Roger Pau Monne      libxl: add is_default checkers for string and timer_mode
>> types
>> Roger Pau Monne      libxl: introduce a way to mark fields as deprecated in
>> the idl
> 
> This or one of the related patches is going to add fields in
> domain_build_info, which will break the ABI. Is this expected/OK?

Oh right -- this needs to be ported to add the fields at the end.

Going back to the 4.10 series, it looks like there are also some "shim
host" patches having to do with enabling CPUID faulting in the guest.
Do we need to backport those to 4.9 and 4.8 as well?  ISTR they may rely
on some hypervisor infrastructure which would then also need to be
backported.

But PVH shim guests seemed to boot fine under 4.9 / 4.8 without those
patches, so I'm not sure how critical they are.

 -George

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