Re: xsave=0 workaround needed on 3.2 kernels with Xen 4.1 or Xen-unstable.

[Matt Wilson <msw@amazon.com>]

On Tue, May 08, 2012 at 09:39:57AM -0700, Konrad Rzeszutek Wilk wrote:
> On Mon, May 07, 2012 at 05:41:28PM -0700, AP wrote:
> > On Mon, May 7, 2012 at 5:08 PM, Konrad Rzeszutek Wilk <
> > konrad.wilk@oracle.com> wrote:
> > 
> > This is in the Ubuntu 11.10 kernel:
> > http://kernel.ubuntu.com/git?p=ubuntu/ubuntu-oneiric.git;a=blob;f=arch/x86/xen/enlighten.c;h=ce01f6d63507fd44288989ca0ba81a0f5bf04e3f;hb=HEAD#l812
> > 
> > After some digging around, it looks like this is an Ubuntu 11.10 only patch:
> > http://kernel.ubuntu.com/git?p=ubuntu/ubuntu-oneiric.git;a=commitdiff;h=3f3fba59aa5773836d94799d10b692f9b7ea16a0;hp=5e498fdb19f5b27699f063eb10040612b824160b
> 
> Which seems to say that Amazon's HV is advertising the OXSAVE bit?
> 
> Lets ping them and see if they have some recomendations.

Hi,

The kernel requirements for EC2 are documented in our User Guide here:
http://docs.amazonwebservices.com/AWSEC2/latest/UserGuide/UserProvidedkernels.html#PVGRUB_compatible_kernels

Specifically, there's a callout regarding XSAVE: 
  "Kernels that disable the pv-ops XSAVE hypercall are known to work
   on all instance types, whereas those that enable this hypercall
   will fail to launch in some cases. Similarly, non-pv-ops kernels
   that do not adhere to the Xen 3.0.2 interface might fail to launch
   in some cases."

Apologies for the miswording of the note, it should say something like
"kernels that disable the XSAVE capability" instead.

Cheers,

Matt