KVM: x86/MMU: Factor rmap operations out of mmu.c

[PATCH 0/7] KVM: x86/MMU: Factor rmap operations out of mmu.c

Posted by Ben Gardon 2 years, 9 months ago

Move the basic operations for manipulating an rmap out of mmu.c, into
their own files.

This is the first step in a series of series to split the Shadow MMU out of
mmu.c. Splitting the shadow MMU out results in about a 50% reduction in line
count of mmu.c, from ~7K to ~3.5K. The rmap operations only represent about
10% of the Shadow MMU but are split out first becase the are relatively
self-contained.

This split may also help facilitate the addition of kUnit tests for rmap
manipulation, especially the fiddly bit flag which diferentiates a direct
pointer from a pte_list_desc.

This effort is complimentary to David Matlack's proposal to refactor
the TDP MMU into an arch-neutral implementation because it further
clarifies the distinction between the Shadow MMU and TDP MMU within x86.

This series contains no functional changes. It's just a direct movement
of code from one file to another.

Whether this rmap code should stay in its own file or get merged with
the rest of the shadow MMU code as it is factored out is open for
debate.

Ben Gardon (7):
  KVM: x86/MMU: Move pte_list operations to rmap.c
  KVM: x86/MMU: Move rmap_iterator to rmap.h
  KVM: x86/MMU: Move gfn_to_rmap() to rmap.c
  KVM: x86/MMU: Move rmap_can_add() and rmap_remove() to rmap.c
  KVM: x86/MMU: Move the rmap walk iterator out of mmu.c
  KVM: x86/MMU: Move rmap zap operations to rmap.c
  KVM: x86/MMU: Move rmap_add() to rmap.c

 arch/x86/kvm/Makefile           |   2 +-
 arch/x86/kvm/debugfs.c          |   1 +
 arch/x86/kvm/mmu/mmu.c          | 438 +-------------------------------
 arch/x86/kvm/mmu/mmu_internal.h |   9 +-
 arch/x86/kvm/mmu/rmap.c         | 368 +++++++++++++++++++++++++++
 arch/x86/kvm/mmu/rmap.h         | 106 ++++++++
 6 files changed, 492 insertions(+), 432 deletions(-)
 create mode 100644 arch/x86/kvm/mmu/rmap.c
 create mode 100644 arch/x86/kvm/mmu/rmap.h

-- 
2.39.0.rc0.267.gcb52ba06e7-goog

Re: [PATCH 0/7] KVM: x86/MMU: Factor rmap operations out of mmu.c

Posted by David Matlack 2 years, 9 months ago

On Tue, Dec 06, 2022 at 05:35:54PM +0000, Ben Gardon wrote:
> Move the basic operations for manipulating an rmap out of mmu.c, into
> their own files.

memslot_rmap_alloc() and memslot_rmap_free() from x86.c look like good
candidates to move to rmap.c as well as they are pure setup/teardown.

> 
> This is the first step in a series of series to split the Shadow MMU out of
> mmu.c. Splitting the shadow MMU out results in about a 50% reduction in line
> count of mmu.c, from ~7K to ~3.5K. The rmap operations only represent about
> 10% of the Shadow MMU but are split out first becase the are relatively
> self-contained.
> 
> This split may also help facilitate the addition of kUnit tests for rmap
> manipulation, especially the fiddly bit flag which diferentiates a direct
> pointer from a pte_list_desc.
> 
> This effort is complimentary to David Matlack's proposal to refactor
> the TDP MMU into an arch-neutral implementation because it further
> clarifies the distinction between the Shadow MMU and TDP MMU within x86.
> 
> This series contains no functional changes. It's just a direct movement
> of code from one file to another.
> 
> Whether this rmap code should stay in its own file or get merged with
> the rest of the shadow MMU code as it is factored out is open for
> debate.
> 
> Ben Gardon (7):
>   KVM: x86/MMU: Move pte_list operations to rmap.c
>   KVM: x86/MMU: Move rmap_iterator to rmap.h
>   KVM: x86/MMU: Move gfn_to_rmap() to rmap.c
>   KVM: x86/MMU: Move rmap_can_add() and rmap_remove() to rmap.c
>   KVM: x86/MMU: Move the rmap walk iterator out of mmu.c
>   KVM: x86/MMU: Move rmap zap operations to rmap.c
>   KVM: x86/MMU: Move rmap_add() to rmap.c
> 
>  arch/x86/kvm/Makefile           |   2 +-
>  arch/x86/kvm/debugfs.c          |   1 +
>  arch/x86/kvm/mmu/mmu.c          | 438 +-------------------------------
>  arch/x86/kvm/mmu/mmu_internal.h |   9 +-
>  arch/x86/kvm/mmu/rmap.c         | 368 +++++++++++++++++++++++++++
>  arch/x86/kvm/mmu/rmap.h         | 106 ++++++++
>  6 files changed, 492 insertions(+), 432 deletions(-)
>  create mode 100644 arch/x86/kvm/mmu/rmap.c
>  create mode 100644 arch/x86/kvm/mmu/rmap.h
> 
> -- 
> 2.39.0.rc0.267.gcb52ba06e7-goog
>