Re: [Xen-devel] [PATCH 05/34] xen: is_hvm_domain should evaluate to 0 when !CONFIG_HVM

[Julien Grall <julien.grall@xxxxxxx>]

On 08/21/2018 07:49 PM, Wei Liu wrote:
> On Tue, Aug 21, 2018 at 07:33:56PM +0100, Julien Grall wrote:
> > Hi Wei,
> >
> > On 08/21/2018 05:31 PM, Wei Liu wrote:
> > > On Mon, Aug 20, 2018 at 05:51:28AM -0600, Jan Beulich wrote:
> > > > > > > On 17.08.18 at 17:12, <wei.liu2@xxxxxxxxxx> wrote:
> > > > > Since it is defined in common header file, introduce CONFIG_HVM to
> > > > > Arm to avoid breakage.
> > > > >
> > > > > Signed-off-by: Wei Liu <wei.liu2@xxxxxxxxxx>
> > > > > ---
> > > > >    xen/arch/arm/Kconfig    | 3 +++
> > > > >    xen/include/xen/sched.h | 6 ++++++
> > > > >    2 files changed, 9 insertions(+)
> > > > > ,
> > > > > diff --git a/xen/arch/arm/Kconfig b/xen/arch/arm/Kconfig
> > > > > index 586bc62..c0e969e 100644
> > > > > --- a/xen/arch/arm/Kconfig
> > > > > +++ b/xen/arch/arm/Kconfig
> > > > > @@ -52,6 +52,9 @@ config HAS_ITS
> > > > >            prompt "GICv3 ITS MSI controller support" if EXPERT = "y"
> > > > >            depends on GICV3 && !NEW_VGIC
> > > > > +config HVM
> > > > > +        def_bool y
> > > > I'm not convinced this is a good idea, but I'll let the ARM maintainers
> > > > judge.
> > > Andrew discovered that hvm flag is not set by toolstack so ARM guests
> > > are PV guests to Xen. I think the addition here can be omitted.
> > >
> > > However I would still like to hear from ARM maintainers what guest type
> > > should be set for ARM, because sooner or later I will need to change PV
> > > code as well.
> > >
> > > Grepping for is_{hvm,pv}_* in arch/arm yields no result, but then there
> > > is common code that we need to take care of.
> > Using PV was more a convenience at the time because was not there. The plan
> > is to switch to PVH (see RFC [1]).
> >
> > I will try to find some times this week to rework the patch based on the
> > comments.
> >
> > Cheers,
> >
> > [1] https://lists.xen.org/archives/html/xen-devel/2018-06/msg01537.html
> Yes, switching to PVH in toolstack is ideal.
>
> The problem we discuss here is in the hypervisor. Hypervisor only has
> HVM and PV. What type should ARM guests be? I think with the move to use
> PVH in toolstack, the type in hypervisor should be HVM (as oppose to PV
> now)?
Arm guest are much closer to HVM than PV. So the hypervisor should use 
HVM here.
Cheers,

--
Julien Grall

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