Re: [PATCH v3 0/9] drm/i915: Replace kmap_atomic() with kmap_local_page()

Zhao Liu
2023-12-14T13:07:34Z

Hi maintainers,

Just kindly ping.
May I ask if this refresh version could be merged into the next tree of
the i915?

Thanks,
Zhao

On Sun, Dec 03, 2023 at 09:29:38PM +0800, Zhao Liu wrote:
> Date: Sun, 3 Dec 2023 21:29:38 +0800
> From: Zhao Liu <zhao1.liu@linux.intel.com>
> Subject: [PATCH v3 0/9] drm/i915: Replace kmap_atomic() with
> kmap_local_page()
> X-Mailer: git-send-email 2.34.1
>
> From: Zhao Liu <zhao1.liu@intel.com>
>
> Hi all,
>
> I refreshed this v3 by rebasing v2 [1] on the commit 968f35f4ab1c
> ("Merge tag 'v6.7-rc3-smb3-client-fixes' of git://git.samba.org/sfrench/
> cifs-2.6").
>
> Based on the current code, I rechecked the substitutions in v2 and they
> still stand and are valid, so no code change in v3.
>
> Thanks for all the review! And sorry v2 was missed, I'll pay more
> attention to this v3.
>
>
> Purpose of This Patchset
> ========================
>
> The purpose of this pacthset is to replace all uses of kmap_atomic() in
> i915 with kmap_local_page() because the use of kmap_atomic() is being
> deprecated in favor of kmap_local_page()[2]. And 92b64bd (mm/highmem:
> add notes about conversions from kmap{,_atomic}()) has declared the
> deprecation of kmap_atomic().
>
>
> Motivation for Deprecating kmap_atomic() and Using kmap_local_page()
> ====================================================================
>
> The main difference between atomic and local mappings is that local
> mappings doesn't disable page faults or preemption (the preemption is
> disabled for !PREEMPT_RT case, otherwise it only disables migration).
>
> With kmap_local_page(), we can avoid the often unwanted side effect of
> unnecessary page faults and preemption disables.
>
>
> Patch summary
> =============
>
> Patch 1, 4-6 and 8-9 replace kmap_atomic()/kunmap_atomic() with
> kmap_local_page()/kunmap_local() directly. With these local
> mappings, the page faults and preemption are allowed.
>
> Patch 2 and 7 use memcpy_from_page() and memcpy_to_page() to replace
> kmap_atomic()/kunmap_atomic(). These two variants of memcpy()
> are based on the local mapping, so page faults and preemption
> are also allowed in these two interfaces.
>
> Patch 3 replaces kmap_atomic()/kunmap_atomic() with kmap_local_page()/
> kunmap_local() and also disable page fault since the for special
> handling (pls see the commit message).
>
>
> Reference
> =========
>
> [1]: https://lore.kernel.org/all/20230329073220.3982460-1-zhao1.liu@linux.intel.com/
> [2]: https://lore.kernel.org/all/20220813220034.806698-1-ira.weiny@intel.com
>
>
> Thanks and Best Regards,
> Zhao
>
> ---
> Changlog:
>
> Changes since v2:
> * Rebased on 968f35f4ab1c ("Merge tag 'v6.7-rc3-smb3-client-fixes' of
> git://git.samba.org/sfrench/cifs-2.6").
> * Removed changelog (of v2) in commit message.
> * Fixed typo in cover letter (Fabio).
> * Added Reviewed-by tags from Ira and Fabio.
>
> Changes since v1:
> * Dropped hot plug related description in commit message since it has
> nothing to do with kmap_local_page().
> * Emphasized the motivation for using kmap_local_page() in commit
> message.
> * Rebased patch 1 on f47e630 (drm/i915/gem: Typecheck page lookups) to
> keep the "idx" variable of type pgoff_t here.
> * Used memcpy_from_page() and memcpy_to_page() to replace
> kmap_local_page() + memcpy() in patch 2.
>
> ---
> Zhao Liu (9):
> drm/i915: Use kmap_local_page() in gem/i915_gem_object.c
> drm/i915: Use memcpy_[from/to]_page() in gem/i915_gem_pyhs.c
> drm/i915: Use kmap_local_page() in gem/i915_gem_shmem.c
> drm/i915: Use kmap_local_page() in gem/selftests/huge_pages.c
> drm/i915: Use kmap_local_page() in gem/selftests/i915_gem_coherency.c
> drm/i915: Use kmap_local_page() in gem/selftests/i915_gem_context.c
> drm/i915: Use memcpy_from_page() in gt/uc/intel_uc_fw.c
> drm/i915: Use kmap_local_page() in i915_cmd_parser.c
> drm/i915: Use kmap_local_page() in gem/i915_gem_execbuffer.c
>
> drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c | 10 +++++-----
> drivers/gpu/drm/i915/gem/i915_gem_object.c | 8 +++-----
> drivers/gpu/drm/i915/gem/i915_gem_phys.c | 10 ++--------
> drivers/gpu/drm/i915/gem/i915_gem_shmem.c | 6 ++++--
> drivers/gpu/drm/i915/gem/selftests/huge_pages.c | 6 +++---
> .../gpu/drm/i915/gem/selftests/i915_gem_coherency.c | 12 ++++--------
> .../gpu/drm/i915/gem/selftests/i915_gem_context.c | 8 ++++----
> drivers/gpu/drm/i915/gt/uc/intel_uc_fw.c | 5 +----
> drivers/gpu/drm/i915/i915_cmd_parser.c | 4 ++--
> 9 files changed, 28 insertions(+), 41 deletions(-)
>
> --
> 2.34.1
>