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Message-ID: <ed68d414-ddbc-4472-9663-e6728a1f1eef@redhat.com>
Date: Wed, 2 Apr 2025 00:27:07 +0200
From: Jocelyn Falempe <jfalempe@...hat.com>
To: Ville Syrjälä <ville.syrjala@...ux.intel.com>
Cc: Jani Nikula <jani.nikula@...ux.intel.com>,
Rodrigo Vivi <rodrigo.vivi@...el.com>,
Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
Tvrtko Ursulin <tursulin@...ulin.net>, David Airlie <airlied@...il.com>,
Simona Vetter <simona@...ll.ch>, intel-gfx@...ts.freedesktop.org,
intel-xe@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 4/8] drm/i915/gem: Add i915_gem_object_panic_map()
On 01/04/2025 19:47, Ville Syrjälä wrote:
> On Tue, Apr 01, 2025 at 02:51:10PM +0200, Jocelyn Falempe wrote:
>> Prepare the work for drm_panic support. This is used to map the
>> current framebuffer, so the CPU can overwrite it with the panic
>> message.
>>
>> Signed-off-by: Jocelyn Falempe <jfalempe@...hat.com>
>> ---
>>
>> v5:
>> * Use iosys_map for intel_bo_panic_map().
>>
>> drivers/gpu/drm/i915/display/intel_bo.c | 5 ++++
>> drivers/gpu/drm/i915/display/intel_bo.h | 1 +
>> drivers/gpu/drm/i915/gem/i915_gem_object.h | 2 ++
>> drivers/gpu/drm/i915/gem/i915_gem_pages.c | 29 ++++++++++++++++++++++
>> drivers/gpu/drm/xe/display/intel_bo.c | 10 ++++++++
>> 5 files changed, 47 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/i915/display/intel_bo.c b/drivers/gpu/drm/i915/display/intel_bo.c
>> index fbd16d7b58d9..ac904e9ec7d5 100644
>> --- a/drivers/gpu/drm/i915/display/intel_bo.c
>> +++ b/drivers/gpu/drm/i915/display/intel_bo.c
>> @@ -57,3 +57,8 @@ void intel_bo_describe(struct seq_file *m, struct drm_gem_object *obj)
>> {
>> i915_debugfs_describe_obj(m, to_intel_bo(obj));
>> }
>> +
>> +void intel_bo_panic_map(struct drm_gem_object *obj, struct iosys_map *map)
>> +{
>> + i915_gem_object_panic_map(to_intel_bo(obj), map);
>> +}
>> diff --git a/drivers/gpu/drm/i915/display/intel_bo.h b/drivers/gpu/drm/i915/display/intel_bo.h
>> index ea7a2253aaa5..5b6c63d99786 100644
>> --- a/drivers/gpu/drm/i915/display/intel_bo.h
>> +++ b/drivers/gpu/drm/i915/display/intel_bo.h
>> @@ -23,5 +23,6 @@ struct intel_frontbuffer *intel_bo_set_frontbuffer(struct drm_gem_object *obj,
>> struct intel_frontbuffer *front);
>>
>> void intel_bo_describe(struct seq_file *m, struct drm_gem_object *obj);
>> +void intel_bo_panic_map(struct drm_gem_object *obj, struct iosys_map *map);
>>
>> #endif /* __INTEL_BO__ */
>> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object.h b/drivers/gpu/drm/i915/gem/i915_gem_object.h
>> index a5f34542135c..b16092707ea5 100644
>> --- a/drivers/gpu/drm/i915/gem/i915_gem_object.h
>> +++ b/drivers/gpu/drm/i915/gem/i915_gem_object.h
>> @@ -692,6 +692,8 @@ i915_gem_object_unpin_pages(struct drm_i915_gem_object *obj)
>> int __i915_gem_object_put_pages(struct drm_i915_gem_object *obj);
>> int i915_gem_object_truncate(struct drm_i915_gem_object *obj);
>>
>> +void i915_gem_object_panic_map(struct drm_i915_gem_object *obj, struct iosys_map *map);
>> +
>> /**
>> * i915_gem_object_pin_map - return a contiguous mapping of the entire object
>> * @obj: the object to map into kernel address space
>> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_pages.c b/drivers/gpu/drm/i915/gem/i915_gem_pages.c
>> index 8780aa243105..718bea6474d7 100644
>> --- a/drivers/gpu/drm/i915/gem/i915_gem_pages.c
>> +++ b/drivers/gpu/drm/i915/gem/i915_gem_pages.c
>> @@ -355,6 +355,35 @@ static void *i915_gem_object_map_pfn(struct drm_i915_gem_object *obj,
>> return vaddr ?: ERR_PTR(-ENOMEM);
>> }
>>
>> +/* Map the current framebuffer for CPU access. Called from panic handler, so no
>> + * need to pin or cleanup.
>> + */
>> +void i915_gem_object_panic_map(struct drm_i915_gem_object *obj, struct iosys_map *map)
>> +{
>> + enum i915_map_type has_type;
>> + void *ptr;
>> +
>> + ptr = page_unpack_bits(obj->mm.mapping, &has_type);
>> +
>> +
>> + if (!ptr) {
>> + if (i915_gem_object_has_struct_page(obj))
>> + ptr = i915_gem_object_map_page(obj, I915_MAP_WB);
>> + else
>> + ptr = i915_gem_object_map_pfn(obj, I915_MAP_WB);
>
> WB mapping would require clflushing to make it to the display.
> Is that being done somewhere?
Yes, it's done in intel_panic_flush() in patch 5, otherwise the panic
screen is not displayed.
>
>> +
>> + if (IS_ERR(ptr))
>> + return;
>
> What happens when the mapping fails?
In intel_get_scanout_buffer(), the iosys_map is cleared before calling
this function. Then it checks iosys_map_is_null(), and returns an error
if it is.
I can add a comment, or I can change the function type to return an int,
that would probably be cleaner.
>
>> +
>> + obj->mm.mapping = page_pack_bits(ptr, I915_MAP_WB);
>> + }
>> +
>> + if (i915_gem_object_has_iomem(obj))
>> + iosys_map_set_vaddr_iomem(map, (void __iomem *) ptr);
>> + else
>> + iosys_map_set_vaddr(map, ptr);
>> +}
>> +
>> /* get, pin, and map the pages of the object into kernel space */
>> void *i915_gem_object_pin_map(struct drm_i915_gem_object *obj,
>> enum i915_map_type type)
>> diff --git a/drivers/gpu/drm/xe/display/intel_bo.c b/drivers/gpu/drm/xe/display/intel_bo.c
>> index 27437c22bd70..c68166a64336 100644
>> --- a/drivers/gpu/drm/xe/display/intel_bo.c
>> +++ b/drivers/gpu/drm/xe/display/intel_bo.c
>> @@ -59,3 +59,13 @@ void intel_bo_describe(struct seq_file *m, struct drm_gem_object *obj)
>> {
>> /* FIXME */
>> }
>> +
>> +void intel_bo_panic_map(struct drm_gem_object *obj, struct iosys_map *map)
>> +{
>> + struct xe_bo *bo = gem_to_xe_bo(obj);
>> + int ret;
>> +
>> + ret = ttm_bo_vmap(&bo->ttm, map);
>> + if (ret)
>> + iosys_map_clear(map);
>> +}
>> --
>> 2.49.0
>
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