Re: [Xen-devel] Xen's Linux kernel config options V2

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Fri, 6 Feb 2015, Luis R. Rodriguez wrote:
> On Fri, Feb 6, 2015 at 4:07 AM, Stefano Stabellini
> <stefano.stabellini@xxxxxxxxxxxxx> wrote:
> > On Thu, 5 Feb 2015, Luis R. Rodriguez wrote:
> >> On Wed, Feb 4, 2015 at 6:57 AM, Stefano Stabellini
> >> <stefano.stabellini@xxxxxxxxxxxxx> wrote:
> >> > On Wed, 4 Feb 2015, David Vrabel wrote:
> >> >> On 16/12/14 16:21, Juergen Gross wrote:
> >> >> > Hi,
> >> >> >
> >> >> > This is a design proposal for a rework of the config options on the
> >> >> > Linux kernel which are related to Xen.
> >> >> >
> >> >> > The need to do so arose from the fact that it is currently not
> >> >> > possible to build the Xen frontend drivers for a non-pvops kernel,
> >> >> > e.g. to run them in a HVM-domain. There are more drawbacks in the
> >> >> > current config options to which I'll come later.
> >> >> >
> >> >> > Option                          Selects                 Depends
> >> >> > ----------------------------------------------------------------------
> >> >> > XEN
> >> >> >   XEN_PV(x86)                   XEN_HAVE_PVMMU
> >> >> >                                 PARAVIRT
> >> >> >                                 PARAVIRT_CLOCK
> >> >> >   XEN_PVH(x86)                  XEN_PVHVM
> >> >> >                                 PARAVIRT
> >> >> >                                 PARAVIRT_CLOCK
> >> >> >   XEN_PVHVM                     PARAVIRT
> >> >> >                                 PARAVIRT_CLOCK
> >> >
> >> > PARAVIRT_CLOCK and PARAVIRT are x86 specific.
> >> > Given that there is no CONFIG_PV or CONFIG_PVH or even CONFIG_PVHVM on
> >> > arm and arm64 as there is just one type of guest, I would rather just
> >> > have CONFIG_XEN there.
> >>
> >> Interesting, right now we have as part of the recommended change for
> >> XEN_BACKEND:
> >>
> >> Option                          Selects                 Depends
> >> ----------------------------------------------------------------------
> >> XEN
> >>   XEN_BACKEND                   SWIOTLB_XEN(arm,arm64)  XEN_PV(x86) ||
> >>                                                         XEN_PVH(x86) ||
> >>                                                         XEN_PVHVM
> >>
> >> How would we ensure to enable XEN_BACKEND for arm then?
> >
> > I thought that you wanted to turn XEN_BACKEND into a user selectable
> > option.  On arm and arm64 this option wouldn't depend on anything
> > (except CONFIG_XEN).
> 
> OK sure, that maps to this dependency list then:
> 
> ARM || ARM64 || ( X86 && (XEN_PV || XEN_PVH || XEN_PVHVM )

And CONFIG_XEN, right?


> >> >> >   XEN_BACKEND                   SWIOTLB_XEN(arm,arm64)  XEN_PV(x86) ||
> >> >> >                                                         XEN_PVH(x86) 
> >> >> > ||
> >> >> >                                                         XEN_PVHVM
> >> >> >     XEN_BLKDEV_BACKEND
> >> >> >     XEN_PCIDEV_BACKEND(x86)
> >> >> >     XEN_SCSI_BACKEND
> >> >> >     XEN_NETDEV_BACKEND
> >> >> >   PCI_XEN(x86)                  SWIOTLB_XEN
> >> >> >   XEN_DOM0                      XEN_BACKEND             XEN_PV(x86) ||
> >> >> >                                 PCI_XEN(x86)            XEN_PVH(x86)
> >> >> >     XEN_ACPI_HOTPLUG_MEMORY                             XEN_STUB
> >> >> >     XEN_ACPI_HOTPLUG_CPU                                XEN_STUB
> >> >> >     XEN_MCE_LOG(x86)
> >> >> >   XEN_MAX_DOMAIN_MEMORY(x86)
> >> >> >   XEN_SAVE_RESTORE(x86)
> >> >> >   XEN_DEBUG_FS
> >> >> >   XEN_WDT
> >> >> >   XEN_BALLOON
> >> >> >     XEN_SELFBALLOONING                                  XEN_TMEM
> >> >> >     XEN_BALLOON_MEMORY_HOTPLUG
> >> >> >     XEN_SCRUB_PAGES
> >> >> >   XENFS                         XEN_PRIVCMD
> >> >> >     XEN_COMPAT_XENFS
> >> >> >   XEN_SYS_HYPERVISOR
> >> >> >   XEN_DEV_EVTCHN
> >> >> >   XEN_GNTDEV
> >> >> >   XEN_GRANT_DEV_ALLOC
> >> >> >   SWIOTLB_XEN
> >> >> >   XEN_TMEM
> >> >
> >> > not available on arm and arm64
> >>
> >> Can you clarify if you meant only XEN_TMEM or all the above here?
> >
> > Only TMEM, sorry for being terse
> 
> That was listed as one of the example Kconfig entries which are
> currently not available on other architectures despite not being
> architecture specific, the other one being XEN_DEBUG_FS. So to be
> clear -- do we not want XEN_TMEM for arm in the future ?

Sure, but it is on nobody's roadmap at the moment.


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