[v11,0/4] riscv: Create and document PR_RISCV_SET_ICACHE_FLUSH_CTX prctl

Message

Charlie Jenkins Feb. 12, 2024, 11:36 p.m. UTC

Improve the performance of icache flushing by creating a new prctl flag
PR_RISCV_SET_ICACHE_FLUSH_CTX. The interface is left generic to allow
for future expansions such as with the proposed J extension [1].

Documentation is also provided to explain the use case.

Patch sent to add PR_RISCV_SET_ICACHE_FLUSH_CTX to man-pages [2].

[1] https://github.com/riscv/riscv-j-extension
[2] https://lore.kernel.org/linux-man/[e-mail]

Signed-off-by: Charlie Jenkins <[e-mail]>
---
Changes in v11:
- Add back PR_RISCV_CTX_SW_FENCEI_OFF (Samuel)
- Fix under nosmp (Samuel)
- Change set_prev_cpu (Samuel)
- Fixup example testcase in docs
- Change wording of documentation slightly (Alejandor Colomar)
- Link to v10: https://lore.kernel.org/r/[e-mail]

Changes in v10:
- Fix fence.i condition to properly only flush on migration (Alex)
- Fix documentation wording (Alex)
- Link to v9: https://lore.kernel.org/r/[e-mail]

Changes in v9:
- Remove prev_cpu from mm (Alex)
- Link to v8: https://lore.kernel.org/r/[e-mail]

Changes in v8:
- Only flush icache if migrated to different cpu (Alex)
- Move flushing to switch_to to catch per-thread flushing properly
- Link to v7: https://lore.kernel.org/r/[e-mail]

Changes in v7:
- Change "per_thread" parameter to "scope" and provide constants for the
  parameter.
- Link to v6: https://lore.kernel.org/r/[e-mail]

Changes in v6:
- Fixup documentation formatting
- Link to v5: https://lore.kernel.org/r/[e-mail]

Changes in v5:
- Minor documentation changes (Randy)
- Link to v4: https://lore.kernel.org/r/[e-mail]

Changes in v4:
- Add OFF flag to disallow fence.i in userspace (Atish)
- Fix documentation issues (Atish)
- Link to v3: https://lore.kernel.org/r/[e-mail]

Changes in v3:
- Check if value force_icache_flush set on thread, rather than in mm
  twice (Clément)
- Link to v2: https://lore.kernel.org/r/[e-mail]

Changes in v2:
- Fix kernel-doc comment (Conor)
- Link to v1: https://lore.kernel.org/r/[e-mail]

---
Charlie Jenkins (4):
      riscv: Remove unnecessary irqflags processor.h include
      riscv: Include riscv_set_icache_flush_ctx prctl
      documentation: Document PR_RISCV_SET_ICACHE_FLUSH_CTX prctl
      cpumask: Add assign cpu

 Documentation/arch/riscv/cmodx.rst |  98 ++++++++++++++++++++++++++++++++++
 Documentation/arch/riscv/index.rst |   1 +
 arch/riscv/include/asm/irqflags.h  |   1 -
 arch/riscv/include/asm/mmu.h       |   2 +
 arch/riscv/include/asm/processor.h |  12 +++++
 arch/riscv/include/asm/switch_to.h |  23 ++++++++
 arch/riscv/mm/cacheflush.c         | 105 +++++++++++++++++++++++++++++++++++++
 arch/riscv/mm/context.c            |  18 +++++--
 include/linux/cpumask.h            |  16 ++++++
 include/uapi/linux/prctl.h         |   6 +++
 kernel/sys.c                       |   6 +++
 11 files changed, 282 insertions(+), 6 deletions(-)
---
base-commit: 6613476e225e090cc9aad49be7fa504e290dd33d
change-id: 20231117-fencei-f9f60d784fa0

Comments

Charlie Jenkins March 5, 2024, 11:22 p.m. UTC | #1

On Mon, Feb 12, 2024 at 03:36:25PM -0800, Charlie Jenkins wrote:
> Improve the performance of icache flushing by creating a new prctl flag
> PR_RISCV_SET_ICACHE_FLUSH_CTX. The interface is left generic to allow
> for future expansions such as with the proposed J extension [1].
> 
> Documentation is also provided to explain the use case.
> 
> Patch sent to add PR_RISCV_SET_ICACHE_FLUSH_CTX to man-pages [2].
> 
> [1] https://github.com/riscv/riscv-j-extension
> [2] https://lore.kernel.org/linux-man/[e-mail]
> 
> Signed-off-by: Charlie Jenkins <[e-mail]>
> ---
> Changes in v11:
> - Add back PR_RISCV_CTX_SW_FENCEI_OFF (Samuel)
> - Fix under nosmp (Samuel)
> - Change set_prev_cpu (Samuel)
> - Fixup example testcase in docs
> - Change wording of documentation slightly (Alejandor Colomar)
> - Link to v10: https://lore.kernel.org/r/[e-mail]
> 
> Changes in v10:
> - Fix fence.i condition to properly only flush on migration (Alex)
> - Fix documentation wording (Alex)
> - Link to v9: https://lore.kernel.org/r/[e-mail]
> 
> Changes in v9:
> - Remove prev_cpu from mm (Alex)
> - Link to v8: https://lore.kernel.org/r/[e-mail]
> 
> Changes in v8:
> - Only flush icache if migrated to different cpu (Alex)
> - Move flushing to switch_to to catch per-thread flushing properly
> - Link to v7: https://lore.kernel.org/r/[e-mail]
> 
> Changes in v7:
> - Change "per_thread" parameter to "scope" and provide constants for the
>   parameter.
> - Link to v6: https://lore.kernel.org/r/[e-mail]
> 
> Changes in v6:
> - Fixup documentation formatting
> - Link to v5: https://lore.kernel.org/r/[e-mail]
> 
> Changes in v5:
> - Minor documentation changes (Randy)
> - Link to v4: https://lore.kernel.org/r/[e-mail]
> 
> Changes in v4:
> - Add OFF flag to disallow fence.i in userspace (Atish)
> - Fix documentation issues (Atish)
> - Link to v3: https://lore.kernel.org/r/[e-mail]
> 
> Changes in v3:
> - Check if value force_icache_flush set on thread, rather than in mm
>   twice (Clément)
> - Link to v2: https://lore.kernel.org/r/[e-mail]
> 
> Changes in v2:
> - Fix kernel-doc comment (Conor)
> - Link to v1: https://lore.kernel.org/r/[e-mail]
> 
> ---
> Charlie Jenkins (4):
>       riscv: Remove unnecessary irqflags processor.h include
>       riscv: Include riscv_set_icache_flush_ctx prctl
>       documentation: Document PR_RISCV_SET_ICACHE_FLUSH_CTX prctl
>       cpumask: Add assign cpu
> 
>  Documentation/arch/riscv/cmodx.rst |  98 ++++++++++++++++++++++++++++++++++
>  Documentation/arch/riscv/index.rst |   1 +
>  arch/riscv/include/asm/irqflags.h  |   1 -
>  arch/riscv/include/asm/mmu.h       |   2 +
>  arch/riscv/include/asm/processor.h |  12 +++++
>  arch/riscv/include/asm/switch_to.h |  23 ++++++++
>  arch/riscv/mm/cacheflush.c         | 105 +++++++++++++++++++++++++++++++++++++
>  arch/riscv/mm/context.c            |  18 +++++--
>  include/linux/cpumask.h            |  16 ++++++
>  include/uapi/linux/prctl.h         |   6 +++
>  kernel/sys.c                       |   6 +++
>  11 files changed, 282 insertions(+), 6 deletions(-)
> ---
> base-commit: 6613476e225e090cc9aad49be7fa504e290dd33d
> change-id: 20231117-fencei-f9f60d784fa0
> -- 
> - Charlie
> 

Copy Samuel Holland on this patch.

- Charlie