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    SubjectRe: [PATCH 13/24] xen/arm: get privilege status
    On Wed, 1 Aug 2012, Konrad Rzeszutek Wilk wrote:
    > On Fri, Jul 27, 2012 at 03:33:50PM +0100, Ian Campbell wrote:
    > > On Fri, 2012-07-27 at 15:25 +0100, Stefano Stabellini wrote:
    > > > On Fri, 27 Jul 2012, Ian Campbell wrote:
    > > > > On Thu, 2012-07-26 at 16:33 +0100, Stefano Stabellini wrote:
    > > > > > Use Xen features to figure out if we are privileged.
    > > > > >
    > > > > > XENFEAT_dom0 was introduced by 23735 in xen-unstable.hg.
    > > > > >
    > > > > > Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
    > > > > > ---
    > > > > > arch/arm/xen/enlighten.c | 7 +++++++
    > > > > > include/xen/interface/features.h | 3 +++
    > > > > > 2 files changed, 10 insertions(+), 0 deletions(-)
    > > > > >
    > > > > > diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c
    > > > > > index dc68074..2e013cf 100644
    > > > > > --- a/arch/arm/xen/enlighten.c
    > > > > > +++ b/arch/arm/xen/enlighten.c
    > > > > > @@ -2,6 +2,7 @@
    > > > > > #include <xen/interface/xen.h>
    > > > > > #include <xen/interface/memory.h>
    > > > > > #include <xen/platform_pci.h>
    > > > > > +#include <xen/features.h>
    > > > > > #include <asm/xen/hypervisor.h>
    > > > > > #include <asm/xen/hypercall.h>
    > > > > > #include <linux/module.h>
    > > > > > @@ -58,6 +59,12 @@ int __init xen_guest_init(void)
    > > > > > }
    > > > > > xen_domain_type = XEN_HVM_DOMAIN;
    > > > > >
    > > > > > + xen_setup_features();
    > > > > > + if (xen_feature(XENFEAT_dom0))
    > > > > > + xen_start_info->flags |= SIF_INITDOMAIN|SIF_PRIVILEGED;
    > > > > > + else
    > > > > > + xen_start_info->flags &= ~(SIF_INITDOMAIN|SIF_PRIVILEGED);
    > > > >
    > > > > What happens here on platforms prior to hypervisor changeset 23735?
    > > >
    > > > It wouldn't work.
    > > > Considering that we are certainly not going to backport ARM support to
    > > > Xen 4.1, and that both ARM and XENFEAT_dom0 will be present in Xen 4.2,
    > > > do we really need to support the Xen unstable changesets between ARM was
    > > > introduced and XENFEAT_dom0 appeared?
    >
    > So should it just panic and say "AAAAAAH"?

    I could panic if I find out that XENFEAT_dom0 is unimplemented but
    actually I only get to know if it is available...


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