Re: [Xen-devel] [PATCH v3 17/17] libxl/arm: Initialize domain param HVM_PARAM_CALLBACK_IRQ

[Julien Grall <julien.grall@xxxxxxx>]

Hi Wei,

On 07/07/16 17:15, Wei Liu wrote:
> On Tue, Jul 05, 2016 at 11:12:47AM +0800, Shannon Zhao wrote:
> > From: Shannon Zhao <shannon.zhao@xxxxxxxxxx>
> >
> > The guest kernel will get the event channel interrupt information via
> > domain param HVM_PARAM_CALLBACK_IRQ. Initialize it here.
> >
> > Signed-off-by: Shannon Zhao <shannon.zhao@xxxxxxxxxx>
> > ---
> >   tools/libxl/libxl_arm.c | 11 +++++++++++
> >   1 file changed, 11 insertions(+)
> >
> > diff --git a/tools/libxl/libxl_arm.c b/tools/libxl/libxl_arm.c
> > index bc38318..acacba0 100644
> > --- a/tools/libxl/libxl_arm.c
> > +++ b/tools/libxl/libxl_arm.c
> > @@ -900,8 +900,19 @@ int libxl__arch_domain_init_hw_description(libxl__gc *gc,
> >                                              struct xc_dom_image *dom)
> >   {
> >       int rc;
> > +    uint64_t val;
> >
> >       assert(info->type == LIBXL_DOMAIN_TYPE_PV);
> > +
> > +    /* Set the value of domain param HVM_PARAM_CALLBACK_IRQ. */
> > +    val = (uint64_t)HVM_PARAM_CALLBACK_TYPE_PPI << 56;
> > +    val |= (2 << 8); /* Active-low level-sensitive  */
> Please avoid using magic numbers here -- 56, 2 and 8.
The magic numbers are described in public/hvm/params.h however there is 
no defines associated to them.
The public header would need to be updated if we don't want the value 
hardcoded in libxl.
> Another question to Julien and Stefano: is it normal for ARM guest to
> use hvm callback vector?
Yes. The HVM callback vector is used by ACPI guest to find the PPI 
(per-cpu interrupt) which will be used to notify event.
This is how DOM0 is using ACPI on ARM (see [1]), I don't think we should 
differ here.
BTW, I have noticed that the design doc is only available on the ML.
Shannon, would it be possible to send a patch to add it in docs/misc/arm?

[2] https://lists.xen.org/archives/html/xen-devel/2015-11/msg00488.html

Regards,

--
Julien Grall

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