[PATCH v2 0/1]

[PATCH v2 0/1]

[Michael Cheng]

To align with the discussion in [1][2], this patch series drops all usage of    
wbvind_on_all_cpus within i915 by either replacing the call with certain        
drm clflush helpers, or reverting to a previous logic.                          
                                                                                 
[1]. https://lists.freedesktop.org/archives/dri-devel/2021-November/330928.html 
[2]. https://patchwork.freedesktop.org/patch/475752/?series=99991&rev=5 

v2 (Michael Cheng) : Per feedback from Thomas and Tvrtko, this series should be
split into two parts; First part is to unblock i915 from build errors and 
second part will focus on implementing range flushes on the propose reverts.


Michael Cheng (1):
  i915/gem: drop wbinvd_on_all_cpus usage

 drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c | 9 ++-------
 1 file changed, 2 insertions(+), 7 deletions(-)

-- 
2.25.1

[PATCH v2 1/1] i915/gem: drop wbinvd_on_all_cpus usage

[Michael Cheng]

Previous concern with using drm_clflush_sg was that we don't know what the
sg_table is pointing to, thus the usage of wbinvd_on_all_cpus to flush
everything at once to avoid paranoia.

To make i915 more architecture-neutral and be less paranoid, lets attempt to
use drm_clflush_sg to flush the pages for when the GPU wants to read
from main memory.

Signed-off-by: Michael Cheng <michael.cheng@intel.com>
---
 drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c | 9 ++-------
 1 file changed, 2 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c b/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c
index f5062d0c6333..b0a5baaebc43 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c
@@ -8,6 +8,7 @@
 #include <linux/highmem.h>
 #include <linux/dma-resv.h>
 #include <linux/module.h>
+#include <drm/drm_cache.h>
 
 #include <asm/smp.h>
 
@@ -250,16 +251,10 @@ static int i915_gem_object_get_pages_dmabuf(struct drm_i915_gem_object *obj)
 	 * DG1 is special here since it still snoops transactions even with
 	 * CACHE_NONE. This is not the case with other HAS_SNOOP platforms. We
 	 * might need to revisit this as we add new discrete platforms.
-	 *
-	 * XXX: Consider doing a vmap flush or something, where possible.
-	 * Currently we just do a heavy handed wbinvd_on_all_cpus() here since
-	 * the underlying sg_table might not even point to struct pages, so we
-	 * can't just call drm_clflush_sg or similar, like we do elsewhere in
-	 * the driver.
 	 */
 	if (i915_gem_object_can_bypass_llc(obj) ||
 	    (!HAS_LLC(i915) && !IS_DG1(i915)))
-		wbinvd_on_all_cpus();
+		drm_clflush_sg(pages);
 
 	sg_page_sizes = i915_sg_dma_sizes(pages->sgl);
 	__i915_gem_object_set_pages(obj, pages, sg_page_sizes);
-- 
2.25.1

[PATCH v2 1/1] i915/gem: drop wbinvd_on_all_cpus usage

[Michael Cheng]

Previous concern with using drm_clflush_sg was that we don't know what the
sg_table is pointing to, thus the usage of wbinvd_on_all_cpus to flush
everything at once to avoid paranoia.

To make i915 more architecture-neutral and be less paranoid, lets attempt to
use drm_clflush_sg to flush the pages for when the GPU wants to read
from main memory.

Signed-off-by: Michael Cheng <michael.cheng@intel.com>
---
 drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c | 9 ++-------
 1 file changed, 2 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c b/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c
index f5062d0c6333..b0a5baaebc43 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c
@@ -8,6 +8,7 @@
 #include <linux/highmem.h>
 #include <linux/dma-resv.h>
 #include <linux/module.h>
+#include <drm/drm_cache.h>
 
 #include <asm/smp.h>
 
@@ -250,16 +251,10 @@ static int i915_gem_object_get_pages_dmabuf(struct drm_i915_gem_object *obj)
 	 * DG1 is special here since it still snoops transactions even with
 	 * CACHE_NONE. This is not the case with other HAS_SNOOP platforms. We
 	 * might need to revisit this as we add new discrete platforms.
-	 *
-	 * XXX: Consider doing a vmap flush or something, where possible.
-	 * Currently we just do a heavy handed wbinvd_on_all_cpus() here since
-	 * the underlying sg_table might not even point to struct pages, so we
-	 * can't just call drm_clflush_sg or similar, like we do elsewhere in
-	 * the driver.
 	 */
 	if (i915_gem_object_can_bypass_llc(obj) ||
 	    (!HAS_LLC(i915) && !IS_DG1(i915)))
-		wbinvd_on_all_cpus();
+		drm_clflush_sg(pages);
 
 	sg_page_sizes = i915_sg_dma_sizes(pages->sgl);
 	__i915_gem_object_set_pages(obj, pages, sg_page_sizes);
-- 
2.25.1