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>,
Dave Hansen <dave.hansen@intel.com>
Subject: [Intel-gfx] [PATCH v2 8/9] drm/i915: Use kmap_local_page() in i915_cmd_parser.c
Date: Wed, 29 Mar 2023 15:32:19 +0800 [thread overview]
Message-ID: <20230329073220.3982460-9-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], and this patch converts the call from
kmap_atomic() to 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.
There're 2 reasons why function copy_batch() doesn't need to disable
pagefaults and preemption for mapping:
1. The flush operation is safe. In i915_cmd_parser.c, copy_batch() calls
drm_clflush_virt_range() to use CLFLUSHOPT or WBINVD to flush.
Since CLFLUSHOPT is global on x86 and WBINVD is called on each cpu
in drm_clflush_virt_range(), the flush operation is global.
2. Any context switch caused by preemption or page faults (page fault
may cause sleep) doesn't affect the validity of local mapping.
Therefore, copy_batch() is a function where the use of
kmap_local_page() in place of kmap_atomic() is correctly suited.
Convert the calls of kmap_atomic() / kunmap_atomic() to
kmap_local_page() / kunmap_local().
[1]: https://lore.kernel.org/all/20220813220034.806698-1-ira.weiny@intel.com
v2:
* Dropped hot plug related description since it has nothing to do with
kmap_local_page().
* No code change since v1, and added description of the motivation of
using kmap_local_page().
Suggested-by: Dave Hansen <dave.hansen@intel.com>
Suggested-by: Ira Weiny <ira.weiny@intel.com>
Suggested-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
---
Suggested by credits:
Dave: Referred to his explanation about cache flush.
Ira: Referred to his task document, review comments and explanation
about cache flush.
Fabio: Referred to his boiler plate commit message and his description
about why kmap_local_page() should be preferred.
---
drivers/gpu/drm/i915/i915_cmd_parser.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_cmd_parser.c b/drivers/gpu/drm/i915/i915_cmd_parser.c
index ddf49c2dbb91..2905df83e180 100644
--- a/drivers/gpu/drm/i915/i915_cmd_parser.c
+++ b/drivers/gpu/drm/i915/i915_cmd_parser.c
@@ -1211,11 +1211,11 @@ static u32 *copy_batch(struct drm_i915_gem_object *dst_obj,
for (n = offset >> PAGE_SHIFT; remain; n++) {
int len = min(remain, PAGE_SIZE - x);
- src = kmap_atomic(i915_gem_object_get_page(src_obj, n));
+ src = kmap_local_page(i915_gem_object_get_page(src_obj, n));
if (src_needs_clflush)
drm_clflush_virt_range(src + x, len);
memcpy(ptr, src + x, len);
- kunmap_atomic(src);
+ kunmap_local(src);
ptr += len;
remain -= len;
--
2.34.1
next prev parent reply other threads:[~2023-03-29 7:25 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 ` [Intel-gfx] [PATCH v2 3/9] drm/i915: Use kmap_local_page() in gem/i915_gem_shmem.c Zhao Liu
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 ` Zhao Liu [this message]
2023-03-31 3:36 ` [Intel-gfx] [PATCH v2 8/9] drm/i915: Use kmap_local_page() in i915_cmd_parser.c 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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