Re: [Xen-devel] Xen's Linux kernel config options v3

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Sat, 7 Feb 2015, Luis R. Rodriguez wrote:
> This is a third respin for a design proposal for a rework on the config 
> options
> on the Linux kernel related to Xen. The frist two proposals came from Juergen,
> I'm taking on the work now as some other work I am doing is related to this.
> This third iteration addresses the feedback given on Juergen's last v2
> proposal. Let me know if there are any questions or any further feedback 
> before
> we start addressing the changes.
> 
> Reasons to consider a cleanup / reorganizing of the kconfig options:
> 
> - Everything depends on Xen but that's obviously not right. For instance
>   we want to be able to build Xen frontend drivers for HVM domains without
>   the need for choosing a pvops kernel: currently the frontend drivers need
>   Xen configured which depends on PARAVIRT.
> - XEN should not depend on PAE, we can have HVM guests without PAE.
> - Some features are available for x86 only, in spite of these not being
>   architecture specific, e.g. XEN_DEBUG_FS
> - Be able to build a Dom0 using XEN_PVH(x86) without having to configure
>   XEN_HAVE_PVMMU(x86).
> 
> Current Xen related config options are as follows:
> 
> Legend:
> 
> - The first column are the Xen config options. Indentation in this
>   column reflects the dependency between those options (e.g.
>   XEN_SCSI_BACKEND depends on XEN_BACKEND, which in turn depends on
>   XEN_DOM0, which depends on XEN).
> - The second column shows the options which are selected automatically
>   if the corresponding option in the first column is configured.
> - The last column shows additional dependencies which can't be shown via
>   the indentation level of the first column.
> - Some options or dependencies are architecture specific, they are
>   listed with the architecture requirements in parens (e.g. XEN_TMEM(x86)
>   which is available for x86 only).
> - Non-Xen options are mentioned only if they seem to be really relevant,
>   like e.g. PARAVIRT or BROKEN.
> - All listed options are user selectable, options which are not user 
> selectable but
>   automatic are prefixed with a '*' on the left hand side to make emphasis
> 
> Option                          Selects                 Depends
> ---------------------------------------------------------------------
> XEN                             PARAVIRT_CLOCK(x86)     PARAVIRT(x86)
>                                 XEN_HAVE_PVMMU(x86)
>                                 SWIOTLB_XEN(arm,arm64)
>   PCI_XEN(x86)                  SWIOTLB_XEN
>   XEN_DOM0                                              PCI_XEN(x86)
>     XEN_BACKEND
>       XEN_BLKDEV_BACKEND
>       XEN_PCIDEV_BACKEND(x86)
>       XEN_SCSI_BACKEND
>       XEN_NETDEV_BACKEND
>     XEN_ACPI_HOTPLUG_MEMORY                             XEN_STUB
>     XEN_ACPI_HOTPLUG_CPU                                XEN_STUB
>     XEN_MCE_LOG(x86)
>   XEN_ACPI_PROCESSOR(x86)                             ACPI_PROCESSOR
>                                                       CPU_FREQ
>   XEN_PVHVM(x86)
>     XEN_PVH(x86)
>   XEN_MAX_DOMAIN_MEMORY(x86)
>   XEN_SAVE_RESTORE(x86)
>   XEN_DEBUG_FS(x86)
>   XEN_FBDEV_FRONTEND            XEN_XENBUS_FRONTEND
>                                 INPUT_XEN_KBDDEV_FRONTEND
>   XEN_BLKDEV_FRONTEND           XEN_XENBUS_FRONTEND
>   HVC_XEN
>     HVC_XEN_FRONTEND            XEN_XENBUS_FRONTEND
>   TCG_XEN                       XEN_XENBUS_FRONTEND
>   XEN_PCIDEV_FRONTEND           PCI_XEN
>                                 XEN_XENBUS_FRONTEND
>   XEN_SCSI_FRONTEND             XEN_XENBUS_FRONTEND
>   INPUT_XEN_KBDDEV_FRONTEND     XEN_XENBUS_FRONTEND
>   XEN_WDT
>   XEN_BALLOON
>     XEN_SELFBALLOONING                                  XEN_TMEM
>     XEN_BALLOON_MEMORY_HOTPLUG
>     XEN_SCRUB_PAGES
>   XEN_DEV_EVTCHN
>   XENFS                         XEN_PRIVCMD
>     XEN_COMPAT_XENFS
>   XEN_SYS_HYPERVISOR
>   XEN_XENBUS_FRONTEND
>   XEN_GNTDEV
>   XEN_GRANT_DEV_ALLOC
>   SWIOTLB_XEN
>   XEN_TMEM(x86)
>   XEN_PRIVCMD
>   XEN_STUB(x86_64)                                      BROKEN
>   XEN_ACPI_PROCESSOR(x86)
>   XEN_HAVE_PVMMU
>   XEN_EFI(x64)
>   XEN_NETDEV_FRONTEND           XEN_XENBUS_FRONTEND

It looks good


> After some feedback for the first draft I'd suggest the following:
> 
> Option                          Selects                 Depends
> ----------------------------------------------------------------------
> XEN
>   XEN_PV(x86)                   XEN_HAVE_PVMMU(x86)
>                                 PARAVIRT
>                                 PARAVIRT_CLOCK
>   XEN_PVH(x86)                  XEN_PVHVM
>                                 PARAVIRT
>                                 PARAVIRT_CLOCK
>   XEN_PVHVM(x86)                PARAVIRT
>                                 PARAVIRT_CLOCK
>   XEN_BACKEND                   SWIOTLB_XEN(arm,arm64)  XEN_PV(x86) ||
>                                                         XEN_PVH(x86) ||
>                                                         XEN_PVHVM(x86)
>                               XEN_TMEM(x86)
>                               XEN_PRIVCMD
>     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_ACPI_PROCESSOR(x86)                           ACPI_PROCESSOR
>                                                       CPU_FREQ
>     XEN_SAVE_RESTORE(x86)
>     XEN_DEBUG_FS
>     XEN_WDT
>   XEN_MAX_DOMAIN_MEMORY(x86)                          XEN_HAVE_PVMMU(x86)
>   XEN_BALLOON
>     XEN_SELFBALLOONING                                  XEN_TMEM(x86)
>     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_STUB(x86_64)                                      BROKEN
>   XEN_ACPI_PROCESSOR(x86)
>  *XEN_HAVE_PVMMU(x86)                                 XEN_PV(x86)
>   XEN_EFI(x64)
>   XEN_XENBUS_FRONTEND
> XEN_FRONTEND                    XEN
>                                 XEN_XENBUS_FRONTEND
>   XEN_FBDEV_FRONTEND            INPUT_XEN_KBDDEV_FRONTEND
>   XEN_BLKDEV_FRONTEND
>   HVC_XEN_FRONTEND              HVC_XEN
>   TCG_XEN
>   XEN_PCIDEV_FRONTEND(x86)      PCI_XEN(x86)
>   XEN_SCSI_FRONTEND
>   INPUT_XEN_KBDDEV_FRONTEND
>   XEN_NETDEV_FRONTEND
>   XEN_PLATFORM_PCI(x86)

this one too


> Changes since v2:
> 
>  * Add XEN_ACPI_PROCESSOR (Konrad)
>  * XEN_MAX_DOMAIN_MEMORY(x86) depends on XEN_HAVE_PVMMU(x86) now (Juergen).
>    Juergen will later replace this once he adds > 500 GiB pv-domains
>  * Clarifications on some lose options, we seem to want to keep these
>    user selectable to be able to allow userspace options which do not depend
>    on xen backend / frontends: ballooning, xenfs, sysfs, event dev, gntdev 
> (Jan)
>  * Tons of clarifications on x86 specific options (Stefano), this includes
>    XEN_PVHVM(x86)
> 
>   Luis
> 

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