Re: [Xen-devel] [PATCH] xen: fix initialization of wallclock time for PVHVM on migration

[konrad wilk <konrad.wilk@xxxxxxxxxx>]

On 6/11/2013 8:17 AM, Roger Pau Monnà wrote:
> On 11/06/13 13:59, Jan Beulich wrote:
> > > > > On 11.06.13 at 12:46, Roger Pau Monne <roger.pau@xxxxxxxxxx> wrote:
> > > The initial values of the wallclock time in the shared info page are
> > > set for PVHVM guests when the hypercall page is initialized, since the
> > > hypercall page is not reinitialized on resume, the hypervisor
> > > wallclock time is not properly set on resume.
> > >
> > > Fix it by forcing an update of the wallclock values when the shared
> > > info page is mapped.
> > NACK - this is a guest side bug. After migration, a guest _has_ to
> > re-init the hypercall page, as it may have got migrated between
> > a VMX and an SVM machine, and the hypercall instructions are
> > different between them.
> AFAICS Linux doesn't seem to re-init the hypercall page, see
> xen_arch_hvm_post_suspend at arch/x86/xen/suspend.c, but maybe I'm
> missing something.
You are right. It does not re-init. It is the first time I heard that it 
has to re-init too.
In the past some steps were taken towards re-initing the shared page - 
that (on PVHVM) flat out died during migration (32-bit). Never figured 
out why and Olaf didn't have the time to dig in this.
(git commit 9d02b43dee0d7fb18dfb13a00915550b1a3daa9f).




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