From: Zhao Liu <zhao1.liu@linux.intel.com>
To: "Jani Nikula" <jani.nikula@linux.intel.com>,
"Joonas Lahtinen" <joonas.lahtinen@linux.intel.com>,
"Rodrigo Vivi" <rodrigo.vivi@intel.com>,
"Tvrtko Ursulin" <tvrtko.ursulin@linux.intel.com>,
"David Airlie" <airlied@gmail.com>,
"Daniel Vetter" <daniel@ffwll.ch>,
"Matthew Auld" <matthew.auld@intel.com>,
"Thomas Hellström" <thomas.hellstrom@linux.intel.com>,
"Nirmoy Das" <nirmoy.das@intel.com>,
"Maarten Lankhorst" <maarten.lankhorst@linux.intel.com>,
"Chris Wilson" <chris@chris-wilson.co.uk>,
"Christian König" <christian.koenig@amd.com>,
intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org,
linux-kernel@vger.kernel.org
Cc: "Fabio M . De Francesco" <fmdefrancesco@gmail.com>,
Ira Weiny <ira.weiny@intel.com>, Zhao Liu <zhao1.liu@intel.com>,
Zhenyu Wang <zhenyu.z.wang@intel.com>
Subject: [Intel-gfx] [PATCH v2 3/9] drm/i915: Use kmap_local_page() in gem/i915_gem_shmem.c
Date: Wed, 29 Mar 2023 15:32:14 +0800 [thread overview]
Message-ID: <20230329073220.3982460-4-zhao1.liu@linux.intel.com> (raw)
In-Reply-To: <20230329073220.3982460-1-zhao1.liu@linux.intel.com>
From: Zhao Liu <zhao1.liu@intel.com>
The use of kmap_atomic() is being deprecated in favor of
kmap_local_page()[1].
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 or preemption disables.
In drm/i915/gem/i915_gem_shmem.c, the function shmem_pwrite() need to
disable pagefault to eliminate the potential recursion fault[2]. But
here __copy_from_user_inatomic() doesn't need to disable preemption and
local mapping is valid for sched in/out.
So it can use kmap_local_page() / kunmap_local() with
pagefault_disable() / pagefault_enable() to replace atomic mapping.
[1]: https://lore.kernel.org/all/20220813220034.806698-1-ira.weiny@intel.com
[2]: https://patchwork.freedesktop.org/patch/295840/
v2: No code change since v1, and added description of the motivation of
using kmap_local_page().
Suggested-by: Ira Weiny <ira.weiny@intel.com>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Reviewed-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
---
Suggested by credits:
Ira: Referred to his suggestions about keeping pagefault_disable().
Fabio: Referred to his description about why kmap_local_page() should
be preferred.
---
drivers/gpu/drm/i915/gem/i915_gem_shmem.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_shmem.c b/drivers/gpu/drm/i915/gem/i915_gem_shmem.c
index 37d1efcd3ca6..ad69a79c8b31 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_shmem.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_shmem.c
@@ -475,11 +475,13 @@ shmem_pwrite(struct drm_i915_gem_object *obj,
if (err < 0)
return err;
- vaddr = kmap_atomic(page);
+ vaddr = kmap_local_page(page);
+ pagefault_disable();
unwritten = __copy_from_user_inatomic(vaddr + pg,
user_data,
len);
- kunmap_atomic(vaddr);
+ pagefault_enable();
+ kunmap_local(vaddr);
err = aops->write_end(obj->base.filp, mapping, offset, len,
len - unwritten, page, data);
--
2.34.1
next prev parent reply other threads:[~2023-03-29 7:24 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-29 7:32 [Intel-gfx] [PATCH v2 0/9] drm/i915: Replace kmap_atomic() with kmap_local_page() Zhao Liu
2023-03-29 7:32 ` [Intel-gfx] [PATCH v2 1/9] drm/i915: Use kmap_local_page() in gem/i915_gem_object.c Zhao Liu
2023-03-30 21:56 ` Ira Weiny
2023-03-29 7:32 ` [Intel-gfx] [PATCH v2 2/9] drm/i915: Use memcpy_[from/to]_page() in gem/i915_gem_pyhs.c Zhao Liu
2023-03-30 23:01 ` Ira Weiny
2023-03-29 7:32 ` Zhao Liu [this message]
2023-03-29 7:32 ` [Intel-gfx] [PATCH v2 4/9] drm/i915: Use kmap_local_page() in gem/selftests/huge_pages.c Zhao Liu
2023-03-31 3:04 ` Ira Weiny
2023-03-29 7:32 ` [Intel-gfx] [PATCH v2 5/9] drm/i915: Use kmap_local_page() in gem/selftests/i915_gem_coherency.c Zhao Liu
2023-03-31 3:07 ` Ira Weiny
2023-03-29 7:32 ` [Intel-gfx] [PATCH v2 6/9] drm/i915: Use kmap_local_page() in gem/selftests/i915_gem_context.c Zhao Liu
2023-03-31 3:33 ` Ira Weiny
2023-03-31 8:05 ` Tvrtko Ursulin
2023-03-29 7:32 ` [Intel-gfx] [PATCH v2 7/9] drm/i915: Use memcpy_from_page() in gt/uc/intel_uc_fw.c Zhao Liu
2023-03-29 7:32 ` [Intel-gfx] [PATCH v2 8/9] drm/i915: Use kmap_local_page() in i915_cmd_parser.c Zhao Liu
2023-03-31 3:36 ` Ira Weiny
2023-03-29 7:32 ` [Intel-gfx] [PATCH v2 9/9] drm/i915: Use kmap_local_page() in gem/i915_gem_execbuffer.c Zhao Liu
2023-03-31 4:18 ` Ira Weiny
2023-03-31 11:30 ` Tvrtko Ursulin
2023-03-31 15:32 ` Fabio M. De Francesco
2023-04-10 9:08 ` Zhao Liu
2023-04-12 15:45 ` Tvrtko Ursulin
2023-04-14 10:45 ` Zhao Liu
2023-04-17 11:24 ` Tvrtko Ursulin
2023-04-17 14:53 ` Rodrigo Vivi
2023-10-18 16:19 ` Zhao Liu
2023-10-19 9:02 ` Tvrtko Ursulin
2023-03-29 8:17 ` [Intel-gfx] ✗ Fi.CI.CHECKPATCH: warning for drm/i915: Replace kmap_atomic() with kmap_local_page() Patchwork
2023-03-29 8:18 ` [Intel-gfx] ✗ Fi.CI.SPARSE: " Patchwork
2023-03-29 8:37 ` [Intel-gfx] ✓ Fi.CI.BAT: success " Patchwork
2023-03-29 16:03 ` [Intel-gfx] [PATCH v2 0/9] " Fabio M. De Francesco
2023-03-30 16:00 ` Zhao Liu
2023-03-29 19:51 ` [Intel-gfx] ✓ Fi.CI.IGT: success for " Patchwork
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