Re: [Xen-devel] [PATCH RFC 00/10] x86 passthrough code cleanup

[Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>]

On Fri, Feb 23, 2018 at 10:39:20PM -0600, Doug Goldstein wrote:
> On 2/22/18 11:12 PM, Tian, Kevin wrote:
> >> From: Wei Liu
> >> Sent: Thursday, February 22, 2018 5:47 AM
> >>
> >> Hi all
> >>
> >> At some point I would like to make CONFIG_HVM and CONFIG_PV work.
> >> The
> >> passthrough code is one of the road blocks for that work.
> > 
> > Can you elaborate the motivation of this change? why does someone
> > want to disable HVM or PV logic completely from hypervisor?
> 
> I can say I recall advocating for this at Xen Summit in Cambridge. I
> believe I talked about it in Toronto as well. There are a number of
> users of Xen that would certainly want to ship without all the code
> associated with PV compiled in. Given the nature of design "compromises"
> in many parts of x86 systems there is certainly a non-zero sum of people
> that would likely utilize the ability to remove code that doesn't need
> to be there. I think every individual on this list who has been involved
> in the security has been in a room of @intel.com folks has seen features
> vs security win out many times.
> 
> I don't think its a hard stretch of the imagination to see people
> disabling PV in data centers running newer workloads on PVH and HVM
> only.

Yes, definitely disabling PV will be useful. Right after being able to
use PCI passthrough with PVH.

> I can see the real question being why HVM? That I would say lies
> with the direction of discretionary access controls in Xen vs mandatory
> access controls. To solve for the lack of functionality we've grown
> things like "dmops" and I could certainly see a product like Qubes
> running only PVH domains in the future.
> 
> Since I picked on Qubes I've CC'd Marek.

So, is it going to be an option to have CONFIG_HVM=n and CONFIG_PVH=y at
the same time? While currently we do support Windows, so need
CONFIG_HVM=y, but I can see in some future/alternative version we could
have even that disabled. For example right now we do have
CONFIG_SHADOW_PAGING disabled.

-- 
Best Regards,
Marek Marczykowski-Górecki
Invisible Things Lab
A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?

Attachment: signature.asc
Description: PGP signature

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxxx
https://lists.xenproject.org/mailman/listinfo/xen-devel