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

Tvrtko Ursulin
2023-12-14T13:45:33Z

Hi Zhao,

On 14/12/2023 13:19, Zhao Liu wrote:
> Hi maintainers,
>
> Just kindly ping.
> May I ask if this refresh version could be merged into the next tree of
> the i915?

I certainly spotted your series last week or so but then it slipped my
mind to go through it. Should be able to go through it today or tomorrow.

Regards,

Tvrtko

>
> 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
>>