linux-kernel - Re: [PATCH v3 0/9] drm/i915: Replace kmap_atomic() with kmap_local

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Message-ID: <ZXsA4ojbROLXMkfz@intel.com>
Date:   Thu, 14 Dec 2023 21:19:30 +0800
From:   Zhao Liu <zhao1.liu@...ux.intel.com>
To:     Jani Nikula <jani.nikula@...ux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        Tvrtko Ursulin <tvrtko.ursulin@...ux.intel.com>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Ira Weiny <ira.weiny@...el.com>,
        "Fabio M . De Francesco" <fmdefrancesco@...il.com>,
        intel-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Cc:     Dave Hansen <dave.hansen@...el.com>,
        Zhenyu Wang <zhenyu.z.wang@...el.com>,
        Zhao Liu <zhao1.liu@...el.com>
Subject: Re: [PATCH v3 0/9] drm/i915: Replace kmap_atomic() with
 kmap_local_page()

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@...ux.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@...el.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
>