Re: [PATCH v2 for-4.19 00/13] xen/bitops: Untangle ffs()/fls() infrastructure

["Oleksii K." <oleksii.kurochko@xxxxxxxxx>]

I think we can consider to have this patch series in Xen 4.19 release:
 Release-acked-by: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx> 

~ Oleksii
On Fri, 2024-05-24 at 21:03 +0100, Andrew Cooper wrote:
> bitops.h is a mess.  It has grown organtically over many years, and
> forces
> unreasonable repsonsibilities out into the per-arch stubs.
> 
> Start cleaning it up with ffs() and friends.  Across the board, this
> adds:
> 
>  * Functioning bitops without arch-specific asm
>  * An option for arches to provide more optimal code generation
>  * Compile-time constant folding
>  * Testing at both compile time and during init that the basic
> operations
>    behave according to spec.
> 
> and the only reason this series isn't a net reduction in code alone
> is the
> because of the new unit testing.
> 
> This form is superior in many ways, including getting RISC-V support
> for free.
> 
> v2:
>  * Many changes.  See patches for details
>  * Include the fls() side of the infrastructure too.
> 
> Testing:
>  
> https://gitlab.com/xen-project/people/andyhhp/xen/-/pipelines/1304664544
>   https://cirrus-ci.com/github/andyhhp/xen/
> 
> Series-wide net bloat-o-meter:
> 
>   x86:   up/down: 51/-247 (-196)
>   ARM64: up/down: 40/-400 (-360)
> 
> and PPC64 reproduced in full, just to demonstrate how absurd it was
> to have
> generic_f?s() as static inlines...
> 
>   add/remove: 1/0 grow/shrink: 1/11 up/down: 228/-4832 (-4604)
>   Function                                     old     new   delta
>   init_constructors                              -     220    +220
>   start_xen                                     92     100      +8
>   alloc_heap_pages                            1980    1744    -236
>   xenheap_max_mfn                              360     120    -240
>   free_heap_pages                              784     536    -248
>   find_next_zero_bit                           564     276    -288
>   find_next_bit                                548     260    -288
>   find_first_zero_bit                          444     148    -296
>   find_first_bit                               444     132    -312
>   xmem_pool_free                              1776    1440    -336
>   __do_softirq                                 604     252    -352
>   init_heap_pages                             2328    1416    -912
>   xmem_pool_alloc                             2920    1596   -1324
> 
> 
> Andrew Cooper (12):
>   ppc/boot: Run constructors on boot
>   xen/bitops: Cleanup ahead of rearrangements
>   ARM/bitops: Change find_first_set_bit() to be a define
>   xen/page_alloc: Coerce min(flsl(), foo) expressions to being
> unsigned
>   xen/bitops: Implement generic_f?sl() in lib/
>   xen/bitops: Implement ffs() in common logic
>   x86/bitops: Improve arch_ffs() in the general case
>   xen/bitops: Implement ffsl() in common logic
>   xen/bitops: Replace find_first_set_bit() with ffsl() - 1
>   xen/bitops: Delete find_first_set_bit()
>   xen/bitops: Clean up ffs64()/fls64() definitions
>   xen/bitops: Rearrange the top of xen/bitops.h
> 
> Oleksii Kurochko (1):
>   xen/bitops: Implement fls()/flsl() in common logic
> 
>  xen/arch/arm/include/asm/arm32/bitops.h      |   2 -
>  xen/arch/arm/include/asm/arm64/bitops.h      |  12 --
>  xen/arch/arm/include/asm/bitops.h            |  35 +---
>  xen/arch/ppc/include/asm/bitops.h            |  17 +-
>  xen/arch/ppc/setup.c                         |   2 +
>  xen/arch/x86/guest/xen/xen.c                 |   4 +-
>  xen/arch/x86/hvm/dom0_build.c                |   2 +-
>  xen/arch/x86/hvm/hpet.c                      |   8 +-
>  xen/arch/x86/include/asm/bitops.h            | 114 +++++++------
>  xen/arch/x86/include/asm/pt-contig-markers.h |   2 +-
>  xen/arch/x86/mm.c                            |   2 +-
>  xen/arch/x86/mm/p2m-pod.c                    |   4 +-
>  xen/common/Makefile                          |   1 +
>  xen/common/bitops.c                          |  89 +++++++++++
>  xen/common/page_alloc.c                      |   6 +-
>  xen/common/softirq.c                         |   2 +-
>  xen/drivers/passthrough/amd/iommu_map.c      |   2 +-
>  xen/drivers/passthrough/iommu.c              |   4 +-
>  xen/drivers/passthrough/x86/iommu.c          |   4 +-
>  xen/include/xen/bitops.h                     | 159 ++++++++---------
> --
>  xen/include/xen/boot-check.h                 |  60 +++++++
>  xen/include/xen/compiler.h                   |   3 +-
>  xen/lib/Makefile                             |   2 +
>  xen/lib/generic-ffsl.c                       |  65 ++++++++
>  xen/lib/generic-flsl.c                       |  68 ++++++++
>  25 files changed, 444 insertions(+), 225 deletions(-)
>  create mode 100644 xen/common/bitops.c
>  create mode 100644 xen/include/xen/boot-check.h
>  create mode 100644 xen/lib/generic-ffsl.c
>  create mode 100644 xen/lib/generic-flsl.c
>