Re: [RFC/PATCH v2 00/22] KVM/s390: Hugetlbfs enablement

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FWIW, this patch set has survived some testing on my side (with storage
keys, with VSIE, with both), so I would say that after a respin with some 
patch sqashing we give it some more days for the last reviews and then apply
the whole thing via a topic branch via Martins s390 tree. I will merge
this branch as well to solve the potential conflicts with 
Davids patch ( s390x/mm: cleanup gmap_pte_op_walk() ) which is still
pending in my tree

Christian





On 12/13/2017 01:53 PM, Janosch Frank wrote:
> Since the z10 s390 does support 1M pages, but whereas hugetlbfs
> support was added quite fast, KVM always used standard 4k pages for
> guest backings.
> 
> This patchset adds full support for 1M huge page backings for s390
> KVM guests. I.e. we also support VSIE (nested vms) for these guests
> and are therefore able to run all combinations of backings for all
> layers of guests.
> 
> When running a VSIE guest in a huge page backed guest, we need to
> split some huge pages to be able to set granular protection. This way
> we avoid a prot/unprot cycle if prefixes and VSIE pages containing
> level 3 gmap DAT tables share the same segment, as the prefix has to
> be accessible at all times and the VSIE page has to be write
> protected.
> 
> TODO:
> * Cleanups & Documentation
> * Refactoring to get rid of a lot of indents
> * Find a way to reduce or beautify bit checks on table entries
> * Storage key support for split pages (will be a separate bugfix)
> * Regression testing
> * Testing large setups
> * Testing multi level VSIE
> 
> V2:
> 	* Incorporated changes from David's cleanup
> 	* Now flushing with IDTE_NODAT for protection transfers.
> 	* Added RRBE huge page handling for g2 -> g3 skey emulation
> 	* Added documentation for capability
> 	* Renamed GMAP_ENTRY_* constants
> 	* Added SEGMENT hardware bits constants
> 	* Improved some patch descriptions
> 	* General small improvements
> 	* Introduced pte_from_pmd function
> 
> Accomplished testing:
> l2: KVM guest
> l3: nested KVM guest
> 
> * 1m l2 guests
> * VSIE (l3) 4k and 1m guests on 1m l2
> * 1m l2 -> l2 migration with 4k/1m l3 guests
> * l3 -> l2 migration
> * postcopy works every second try, seems to be QEMU or my setup
> 
> 
> The initial prototype was started by Dominik Dingel. I had the
> pleasure of adding the VSIE part, the protection transfers and the
> optimizations. A huge thanks to Christian and Martin who review(ed)
> and helped debugging/designing.
> 
> Dominik Dingel (2):
>   s390/mm: hugetlb pages within a gmap can not be freed
>   s390/mm: clear huge page storage keys on enable_skey
> 
> Janosch Frank (20):
>   s390/mm: make gmap_protect_range more modular
>   s390/mm: Abstract gmap notify bit setting
>   s390/mm: add gmap PMD invalidation notification
>   s390/mm: Add gmap pmd invalidation and clearing
>   s390/mm: Introduce gmap_pmdp_xchg
>   RFC: s390/mm: Transfer guest pmd protection to host
>   s390/mm: Add huge page dirty sync support
>   s390/mm: Add huge pmd storage key handling
>   s390/mm: Remove superfluous parameter
>   s390/mm: Add gmap_protect_large read protection support
>   s390/mm: Make gmap_read_table EDAT1 compatible
>   s390/mm: Make protect_rmap EDAT1 compatible
>   s390/mm: GMAP read table extensions
>   s390/mm: Add shadow segment code
>   s390/mm: Add VSIE reverse fake case
>   s390/mm: Remove gmap_pte_op_walk
>   s390/mm: Split huge pages if granular protection is needed
>   s390/mm: Enable gmap huge pmd support
>   KVM: s390: Add KVM HPAGE capability
>   RFC: s390/mm: Add gmap lock classes
> 
>  Documentation/virtual/kvm/api.txt |   10 +
>  arch/s390/include/asm/gmap.h      |   39 +-
>  arch/s390/include/asm/pgtable.h   |   18 +-
>  arch/s390/kvm/gaccess.c           |   64 +-
>  arch/s390/kvm/kvm-s390.c          |   19 +-
>  arch/s390/mm/fault.c              |   10 +-
>  arch/s390/mm/gmap.c               | 1275 +++++++++++++++++++++++++++++++++----
>  arch/s390/mm/pageattr.c           |    6 +-
>  arch/s390/mm/pgtable.c            |  176 ++++-
>  include/uapi/linux/kvm.h          |    1 +
>  10 files changed, 1445 insertions(+), 173 deletions(-)
> 

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