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

From: Wei Liu <wei.liu2@citrix.com>
To: Stefano Stabellini <sstabellini@kernel.org>
Cc: Wei Liu <wei.liu2@citrix.com>,
	George Dunlap <George.Dunlap@eu.citrix.com>,
	Andrew Cooper <andrew.cooper3@citrix.com>,
	Ian Jackson <Ian.Jackson@eu.citrix.com>, Tim Deegan <tim@xen.org>,
	Julien Grall <julien.grall@arm.com>,
	Jan Beulich <JBeulich@suse.com>,
	xen-devel <xen-devel@lists.xenproject.org>
Subject: Re: [PATCH 05/34] xen: is_hvm_domain should evaluate to 0 when !CONFIG_HVM
Date: Tue, 21 Aug 2018 21:08:00 +0100	[thread overview]
Message-ID: <20180821200800.guv2jbbxtwpfbza4@citrix.com> (raw)
In-Reply-To: <alpine.DEB.2.10.1808211159190.16354@sstabellini-ThinkPad-X260>

On Tue, Aug 21, 2018 at 11:59:26AM -0700, Stefano Stabellini wrote:
> On Tue, 21 Aug 2018, Julien Grall wrote:
> > 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@citrix.com> wrote:
> > > > > > > Since it is defined in common header file, introduce CONFIG_HVM to
> > > > > > > Arm to avoid breakage.
> > > > > > > 
> > > > > > > Signed-off-by: Wei Liu <wei.liu2@citrix.com>
> > > > > > > ---
> > > > > > >    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.
>  
> +1

OK. In that case, what do you guys think about introducing CONFIG_HVM to
ARM?

Wei.

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