Re: [Xen-devel] [PATCH 09/28] ARM: GICv3 ITS: map device and LPIs to the ITS on physdev_op hypercall

[Julien Grall <julien.grall@xxxxxxx>]

On 31/01/17 10:29, Jaggi, Manish wrote:
> > From: Xen-devel <xen-devel-bounces@xxxxxxxxxxxxx> on behalf of Andre Przywara 
> > <andre.przywara@xxxxxxx>
> > Sent: Tuesday, January 31, 2017 12:01 AM
> > To: Stefano Stabellini; Julien Grall
> > Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx; Vijay Kilari
> > Subject: [Xen-devel] [PATCH 09/28] ARM: GICv3 ITS: map device and LPIs to the 
> > ITS on physdev_op hypercall
> [snip]
> >  int do_physdev_op(int cmd, XEN_GUEST_HANDLE_PARAM(void) arg)
> >  {
> > +    struct physdev_manage_pci manage;
> > +    u32 devid;
> > +    int ret;
> > +
> > +    switch (cmd)
> > +    {
> You might alos need to  PHYSDEVOP_pci_device_add hypercall also.
>
> > +        case PHYSDEVOP_manage_pci_add:
> > +        case PHYSDEVOP_manage_pci_remove:
> > +            if ( copy_from_guest(&manage, arg, 1) != 0 )
> > +                return -EFAULT;
> > +
> > +            devid = manage.bus << 8 | manage.devfn;
> > +            /* Allocate an ITS device table with space for 32 MSIs */
> > +            ret = gicv3_its_map_guest_device(hardware_domain, devid, devid, 5,
> > +                                             cmd == PHYSDEVOP_manage_pci_add);
> Based on 4.9 kernel, is the deivce ID plain sBDF or it is returnedfrom 
> of_msi_map_rid /  iort_msi_map_rid ?
> I believe there needs to be set this as requirement on the calle of hypercall.
The requirement of the hypercall is already defined and cannot be 
changed. So if it does not provide the correct information, then we need 
to find another way to get the DeviceID.
In case of ACPI, we should be able to get those informations from the 
IORT as the segment number is defined in the firmware tables. But for 
Device Tree, we would need DOM0 and Xen to agree on the segment number.
However, I am not sure whether we are going to need those hypercalls 
when Xen will gain support of PCI. There are some discussion to let Xen 
scanning the PCI devices, and therefore the hypercalls will be used.
Today, the hypercall is called by Linux on ARM, but it might not be the 
case in the future. If we decide to implement it today, it means that we 
will not be able to remove it from Linux from compatibility reasons.
So I would be more in favor of having a per-platform list of devices to 
support for the time being. So we can get GICv3 ITS working with Device 
Tree until Xen gain support of PCI. Stefano, Andre, any opinions?
Cheers,

--
Julien Grall

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