Re: [PATCH v3 00/21] x86/xen: untangle PV and PVHVM guest support code

[Boris Ostrovsky]

On 03/15/2017 05:42 AM, Juergen Gross wrote:
> On 14/03/17 18:35, Vitaly Kuznetsov wrote:
>> Changes since v2:
>> - Rebase to 4.11.0-rc1+
>> - XEN_HAVE_PVMMU moved to config XEN_PV [Juergen Gross]
>> - .pin_vcpu kept for x86_hyper_xen_hvm to support PVH Dom0 in future
>>    [Juergen Gross]
>> - 'extern' qualifiers dropped from newly introduced function prototypes
>>   in headers [Juergen Gross]
>> - A couple of #includes added to address build issues with different
>>   configs [kbuild test robot].
>> - Juergen reviewed-bys added (hope they stand with the above mentioned
>>   changes).
> They do.
>
> In case nobody objects I'll take this series for 4.12.

I haven't tried different combinations but the default set (all yes)
passed my tests.

In the light of 5-level page tables patches the most interesting, I
think, would be !CONFIG_XEN_PV.

-boris


>
>
> Juergen
>
>> The series can also be pulled from https://github.com/vittyvk/linux.git
>>  (xen_pv_hvm_split_v3 branch).
>>
>> Some patches are known to produce checkpatch.pl WARNINGS and a couple of
>> ERRORs, I fixed a few (mostly in _hvm* code I split) and I refrained from
>> fixing the rest to make it easier to review. I think that we may leave PV
>> code as it is as sooner or later it will go away.
>>
>> Original description:
>>
>> I have a long-standing idea to separate PV and PVHVM code in kernel and 
>> introduce Kconfig options to make it possible to enable the required
>> parts only breaking the current 'all or nothing' approach.
>>
>> Motivation:
>> - Xen related x86 code in kernel is rather big and it is unclear which
>>   parts of it are required for PV, for HVM or for both. With PVH coming
>>   into picture is becomes even more tangled. It makes it hard to
>>   understand/audit the code.
>>
>> - In some case we may want to avoid bloating kernel by supporting Xen
>>   guests we don't need. In particular, 90% of the code in arch/x86/xen/ is
>>   required to support PV guests and one may require PVHVM support only.
>>
>> - PV guests are supposed to go away one day and such code separation would
>>   help us to get ready.
>>
>> This series adds XEN_PV Kconfig option and makes it possible to build PV-only
>> and PVHVM-only kernels. It also makes it possible to disable Dom0 support.
>>
>> Some patches are rather big but this is mostly just moving code around, no
>> functional changes intended. I smoke tested it with PV-only and PVHVM-only
>> builds, booted and did save/restore test. I also tried the newly introduced
>> PVHv2 guest, it even worked!
>>
>> Vitaly Kuznetsov (21):
>>   x86/xen: separate PV and HVM hypervisors
>>   x86/xen: globalize have_vcpu_info_placement
>>   x86/xen: add CONFIG_XEN_PV to Kconfig
>>   x86/xen: split off enlighten_pvh.c
>>   x86/xen: split off enlighten_hvm.c
>>   x86/xen: split off enlighten_pv.c
>>   x86/xen: split xen_smp_intr_init()/xen_smp_intr_free()
>>   x86/xen: split xen_smp_prepare_boot_cpu()
>>   x86/xen: split xen_cpu_die()
>>   x86/xen: split off smp_hvm.c
>>   x86/xen: split off smp_pv.c
>>   x86/xen: split off mmu_hvm.c
>>   x86/xen: split off mmu_pv.c
>>   x86/xen: split suspend.c for PV and PVHVM guests
>>   x86/xen: put setup.c, pmu.c and apic.c under CONFIG_XEN_PV
>>   x86/xen: define startup_xen for XEN PV only
>>   x86/xen: create stubs for HVM-only builds in page.h
>>   xen/balloon: decorate PV-only parts with #ifdef CONFIG_XEN_PV
>>   xen: create xen_create/destroy_contiguous_region() stubs for PVHVM
>>     only builds
>>   x86/xen: enable PVHVM-only builds
>>   x86/xen: rename some PV-only functions in smp_pv.c
>>
>>  arch/x86/include/asm/hypervisor.h |    3 +-
>>  arch/x86/include/asm/xen/page.h   |   25 +
>>  arch/x86/kernel/cpu/hypervisor.c  |    7 +-
>>  arch/x86/kernel/process_64.c      |    2 +-
>>  arch/x86/xen/Kconfig              |   33 +-
>>  arch/x86/xen/Makefile             |   16 +-
>>  arch/x86/xen/enlighten.c          | 1925 +------------------------
>>  arch/x86/xen/enlighten_hvm.c      |  213 +++
>>  arch/x86/xen/enlighten_pv.c       | 1522 ++++++++++++++++++++
>>  arch/x86/xen/enlighten_pvh.c      |  115 ++
>>  arch/x86/xen/mmu.c                | 2776 +------------------------------------
>>  arch/x86/xen/mmu_hvm.c            |   79 ++
>>  arch/x86/xen/mmu_pv.c             | 2635 +++++++++++++++++++++++++++++++++++
>>  arch/x86/xen/pmu.h                |    5 +
>>  arch/x86/xen/smp.c                |  517 +------
>>  arch/x86/xen/smp.h                |   16 +
>>  arch/x86/xen/smp_hvm.c            |   58 +
>>  arch/x86/xen/smp_pv.c             |  500 +++++++
>>  arch/x86/xen/suspend.c            |   54 -
>>  arch/x86/xen/suspend_hvm.c        |   22 +
>>  arch/x86/xen/suspend_pv.c         |   46 +
>>  arch/x86/xen/xen-head.S           |    4 +
>>  arch/x86/xen/xen-ops.h            |   23 +
>>  drivers/xen/balloon.c             |   30 +-
>>  include/xen/xen-ops.h             |   14 +
>>  25 files changed, 5461 insertions(+), 5179 deletions(-)
>>  create mode 100644 arch/x86/xen/enlighten_hvm.c
>>  create mode 100644 arch/x86/xen/enlighten_pv.c
>>  create mode 100644 arch/x86/xen/enlighten_pvh.c
>>  create mode 100644 arch/x86/xen/mmu_hvm.c
>>  create mode 100644 arch/x86/xen/mmu_pv.c
>>  create mode 100644 arch/x86/xen/smp_hvm.c
>>  create mode 100644 arch/x86/xen/smp_pv.c
>>  create mode 100644 arch/x86/xen/suspend_hvm.c
>>  create mode 100644 arch/x86/xen/suspend_pv.c
>>