Re: [PATCH] x86: Convert shadow-paging to Kconfig

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 19/01/16 09:46, Ian Campbell wrote:
> On Mon, 2016-01-18 at 18:40 +0000, Andrew Cooper wrote:
>> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
> Does this have any impact on migration of either PV or HVM guests?

Not in the slightest.

> What about nested virt?

Nested virt is completely broken with respect to migration.

At no point has anyone considered wiring architectural nesting state
into the migration stream.  Currently, the VM resumes on the far side
with all of its nested setup missing.

>
> Are things which are defined in xen/arch/*/Rules.mk in this way
> overrideable from the old top-level .config or does one need to dive deeper
> to modify them?

Absolutely everything anywhere in the build system is/was configurable
from the top .config

> If it's not configurable from top-level .config today then
> I think it either needs a "depends EXPERT" or for the changelog to make a
> convincing argument why this should be made user selectable.

This patch matches the bigmem patch which has already been accepted (c/s
165f36d).  These two options should match, whatever the outcome of this
discussion is.

> Lastly, Tim is maintainer of the shadow code and should have been CC-d,
> also George as maintainer of the mm stuff might have an interest. Both CC-s 
> added.

Oops yes, although this is an entirely mechanical alteration to an
option which already existed.

~Andrew