If the ttm bo is backed by pages, then it's possible to safely kmap
one page at a time, using kmap_try_from_panic().
Unfortunately there is no way to do the same with ioremap, so it
only supports the kmap case.
This is needed for proper drm_panic support with xe driver.
Signed-off-by: Jocelyn Falempe <jfalempe@redhat.com>
---
v8:
* Added in v8
v9:
* Fix comment in ttm_bo_kmap_try_from_panic(), this can *only* be called
from the panic handler (Christian König)
drivers/gpu/drm/ttm/ttm_bo_util.c | 27 +++++++++++++++++++++++++++
include/drm/ttm/ttm_bo.h | 1 +
2 files changed, 28 insertions(+)
diff --git a/drivers/gpu/drm/ttm/ttm_bo_util.c b/drivers/gpu/drm/ttm/ttm_bo_util.c
index 15cab9bda17f..6912e6dfda25 100644
--- a/drivers/gpu/drm/ttm/ttm_bo_util.c
+++ b/drivers/gpu/drm/ttm/ttm_bo_util.c
@@ -377,6 +377,33 @@ static int ttm_bo_kmap_ttm(struct ttm_buffer_object *bo,
return (!map->virtual) ? -ENOMEM : 0;
}
+/**
+ *
+ * ttm_bo_kmap_try_from_panic
+ *
+ * @bo: The buffer object
+ * @page: The page to map
+ *
+ * Sets up a kernel virtual mapping using kmap_local_page_try_from_panic().
+ * This should only be called from the panic handler, if you make sure the bo
+ * is the one being displayed, so is properly allocated, and protected.
+ *
+ * Returns the vaddr, that you can use to write to the bo, and that you should
+ * pass to kunmap_local() when you're done with this page, or NULL if the bo
+ * is in iomem.
+ */
+void *ttm_bo_kmap_try_from_panic(struct ttm_buffer_object *bo, unsigned long page)
+{
+ if (page + 1 > PFN_UP(bo->resource->size))
+ return NULL;
+
+ if (!bo->resource->bus.is_iomem && bo->ttm->pages && bo->ttm->pages[page])
+ return kmap_local_page_try_from_panic(bo->ttm->pages[page]);
+
+ return NULL;
+}
+EXPORT_SYMBOL(ttm_bo_kmap_try_from_panic);
+
/**
* ttm_bo_kmap
*
diff --git a/include/drm/ttm/ttm_bo.h b/include/drm/ttm/ttm_bo.h
index cf027558b6db..8c0ce3fa077f 100644
--- a/include/drm/ttm/ttm_bo.h
+++ b/include/drm/ttm/ttm_bo.h
@@ -429,6 +429,7 @@ int ttm_bo_init_validate(struct ttm_device *bdev, struct ttm_buffer_object *bo,
int ttm_bo_kmap(struct ttm_buffer_object *bo, unsigned long start_page,
unsigned long num_pages, struct ttm_bo_kmap_obj *map);
void ttm_bo_kunmap(struct ttm_bo_kmap_obj *map);
+void *ttm_bo_kmap_try_from_panic(struct ttm_buffer_object *bo, unsigned long page);
int ttm_bo_vmap(struct ttm_buffer_object *bo, struct iosys_map *map);
void ttm_bo_vunmap(struct ttm_buffer_object *bo, struct iosys_map *map);
int ttm_bo_mmap_obj(struct vm_area_struct *vma, struct ttm_buffer_object *bo);
--
2.49.0
On 6/18/25 11:31, Jocelyn Falempe wrote: > If the ttm bo is backed by pages, then it's possible to safely kmap > one page at a time, using kmap_try_from_panic(). > Unfortunately there is no way to do the same with ioremap, so it > only supports the kmap case. > This is needed for proper drm_panic support with xe driver. > > Signed-off-by: Jocelyn Falempe <jfalempe@redhat.com> Reviewed-by: Christian König <christian.koenig@amd.com> Preferred through drm-misc-next, but feel free to merge it through every branch you want if it makes thinks easier for you. Regards, Christian. > --- > > v8: > * Added in v8 > > v9: > * Fix comment in ttm_bo_kmap_try_from_panic(), this can *only* be called > from the panic handler (Christian König) > > drivers/gpu/drm/ttm/ttm_bo_util.c | 27 +++++++++++++++++++++++++++ > include/drm/ttm/ttm_bo.h | 1 + > 2 files changed, 28 insertions(+) > > diff --git a/drivers/gpu/drm/ttm/ttm_bo_util.c b/drivers/gpu/drm/ttm/ttm_bo_util.c > index 15cab9bda17f..6912e6dfda25 100644 > --- a/drivers/gpu/drm/ttm/ttm_bo_util.c > +++ b/drivers/gpu/drm/ttm/ttm_bo_util.c > @@ -377,6 +377,33 @@ static int ttm_bo_kmap_ttm(struct ttm_buffer_object *bo, > return (!map->virtual) ? -ENOMEM : 0; > } > > +/** > + * > + * ttm_bo_kmap_try_from_panic > + * > + * @bo: The buffer object > + * @page: The page to map > + * > + * Sets up a kernel virtual mapping using kmap_local_page_try_from_panic(). > + * This should only be called from the panic handler, if you make sure the bo > + * is the one being displayed, so is properly allocated, and protected. > + * > + * Returns the vaddr, that you can use to write to the bo, and that you should > + * pass to kunmap_local() when you're done with this page, or NULL if the bo > + * is in iomem. > + */ > +void *ttm_bo_kmap_try_from_panic(struct ttm_buffer_object *bo, unsigned long page) > +{ > + if (page + 1 > PFN_UP(bo->resource->size)) > + return NULL; > + > + if (!bo->resource->bus.is_iomem && bo->ttm->pages && bo->ttm->pages[page]) > + return kmap_local_page_try_from_panic(bo->ttm->pages[page]); > + > + return NULL; > +} > +EXPORT_SYMBOL(ttm_bo_kmap_try_from_panic); > + > /** > * ttm_bo_kmap > * > diff --git a/include/drm/ttm/ttm_bo.h b/include/drm/ttm/ttm_bo.h > index cf027558b6db..8c0ce3fa077f 100644 > --- a/include/drm/ttm/ttm_bo.h > +++ b/include/drm/ttm/ttm_bo.h > @@ -429,6 +429,7 @@ int ttm_bo_init_validate(struct ttm_device *bdev, struct ttm_buffer_object *bo, > int ttm_bo_kmap(struct ttm_buffer_object *bo, unsigned long start_page, > unsigned long num_pages, struct ttm_bo_kmap_obj *map); > void ttm_bo_kunmap(struct ttm_bo_kmap_obj *map); > +void *ttm_bo_kmap_try_from_panic(struct ttm_buffer_object *bo, unsigned long page); > int ttm_bo_vmap(struct ttm_buffer_object *bo, struct iosys_map *map); > void ttm_bo_vunmap(struct ttm_buffer_object *bo, struct iosys_map *map); > int ttm_bo_mmap_obj(struct vm_area_struct *vma, struct ttm_buffer_object *bo);
Hey, On 2025-06-18 15:55, Christian König wrote: > > > On 6/18/25 11:31, Jocelyn Falempe wrote: >> If the ttm bo is backed by pages, then it's possible to safely kmap >> one page at a time, using kmap_try_from_panic(). >> Unfortunately there is no way to do the same with ioremap, so it >> only supports the kmap case. >> This is needed for proper drm_panic support with xe driver. >> >> Signed-off-by: Jocelyn Falempe <jfalempe@redhat.com> > > Reviewed-by: Christian König <christian.koenig@amd.com> > > Preferred through drm-misc-next, but feel free to merge it through every branch you want if it makes thinks easier for you. > Thanks for the ack there. I had to merge this patch through drm-intel-next-queued because of a rework affecting the series. Kind regards, ~Maarten > Regards, > Christian. > >> --- >> >> v8: >> * Added in v8 >> >> v9: >> * Fix comment in ttm_bo_kmap_try_from_panic(), this can *only* be called >> from the panic handler (Christian König) >> >> drivers/gpu/drm/ttm/ttm_bo_util.c | 27 +++++++++++++++++++++++++++ >> include/drm/ttm/ttm_bo.h | 1 + >> 2 files changed, 28 insertions(+) >> >> diff --git a/drivers/gpu/drm/ttm/ttm_bo_util.c b/drivers/gpu/drm/ttm/ttm_bo_util.c >> index 15cab9bda17f..6912e6dfda25 100644 >> --- a/drivers/gpu/drm/ttm/ttm_bo_util.c >> +++ b/drivers/gpu/drm/ttm/ttm_bo_util.c >> @@ -377,6 +377,33 @@ static int ttm_bo_kmap_ttm(struct ttm_buffer_object *bo, >> return (!map->virtual) ? -ENOMEM : 0; >> } >> >> +/** >> + * >> + * ttm_bo_kmap_try_from_panic >> + * >> + * @bo: The buffer object >> + * @page: The page to map >> + * >> + * Sets up a kernel virtual mapping using kmap_local_page_try_from_panic(). >> + * This should only be called from the panic handler, if you make sure the bo >> + * is the one being displayed, so is properly allocated, and protected. >> + * >> + * Returns the vaddr, that you can use to write to the bo, and that you should >> + * pass to kunmap_local() when you're done with this page, or NULL if the bo >> + * is in iomem. >> + */ >> +void *ttm_bo_kmap_try_from_panic(struct ttm_buffer_object *bo, unsigned long page) >> +{ >> + if (page + 1 > PFN_UP(bo->resource->size)) >> + return NULL; >> + >> + if (!bo->resource->bus.is_iomem && bo->ttm->pages && bo->ttm->pages[page]) >> + return kmap_local_page_try_from_panic(bo->ttm->pages[page]); >> + >> + return NULL; >> +} >> +EXPORT_SYMBOL(ttm_bo_kmap_try_from_panic); >> + >> /** >> * ttm_bo_kmap >> * >> diff --git a/include/drm/ttm/ttm_bo.h b/include/drm/ttm/ttm_bo.h >> index cf027558b6db..8c0ce3fa077f 100644 >> --- a/include/drm/ttm/ttm_bo.h >> +++ b/include/drm/ttm/ttm_bo.h >> @@ -429,6 +429,7 @@ int ttm_bo_init_validate(struct ttm_device *bdev, struct ttm_buffer_object *bo, >> int ttm_bo_kmap(struct ttm_buffer_object *bo, unsigned long start_page, >> unsigned long num_pages, struct ttm_bo_kmap_obj *map); >> void ttm_bo_kunmap(struct ttm_bo_kmap_obj *map); >> +void *ttm_bo_kmap_try_from_panic(struct ttm_buffer_object *bo, unsigned long page); >> int ttm_bo_vmap(struct ttm_buffer_object *bo, struct iosys_map *map); >> void ttm_bo_vunmap(struct ttm_buffer_object *bo, struct iosys_map *map); >> int ttm_bo_mmap_obj(struct vm_area_struct *vma, struct ttm_buffer_object *bo); >
On 18/06/2025 15:55, Christian König wrote: > > > On 6/18/25 11:31, Jocelyn Falempe wrote: >> If the ttm bo is backed by pages, then it's possible to safely kmap >> one page at a time, using kmap_try_from_panic(). >> Unfortunately there is no way to do the same with ioremap, so it >> only supports the kmap case. >> This is needed for proper drm_panic support with xe driver. >> >> Signed-off-by: Jocelyn Falempe <jfalempe@redhat.com> > > Reviewed-by: Christian König <christian.koenig@amd.com> > > Preferred through drm-misc-next, but feel free to merge it through every branch you want if it makes thinks easier for you. Thanks, I will see if I can get the whole series through drm-intel-next, or if I can merge #1 and #5 first in drm-misc-next. Best regards, -- Jocelyn > > Regards, > Christian. > >> --- >> >> v8: >> * Added in v8 >> >> v9: >> * Fix comment in ttm_bo_kmap_try_from_panic(), this can *only* be called >> from the panic handler (Christian König) >> >> drivers/gpu/drm/ttm/ttm_bo_util.c | 27 +++++++++++++++++++++++++++ >> include/drm/ttm/ttm_bo.h | 1 + >> 2 files changed, 28 insertions(+) >> >> diff --git a/drivers/gpu/drm/ttm/ttm_bo_util.c b/drivers/gpu/drm/ttm/ttm_bo_util.c >> index 15cab9bda17f..6912e6dfda25 100644 >> --- a/drivers/gpu/drm/ttm/ttm_bo_util.c >> +++ b/drivers/gpu/drm/ttm/ttm_bo_util.c >> @@ -377,6 +377,33 @@ static int ttm_bo_kmap_ttm(struct ttm_buffer_object *bo, >> return (!map->virtual) ? -ENOMEM : 0; >> } >> >> +/** >> + * >> + * ttm_bo_kmap_try_from_panic >> + * >> + * @bo: The buffer object >> + * @page: The page to map >> + * >> + * Sets up a kernel virtual mapping using kmap_local_page_try_from_panic(). >> + * This should only be called from the panic handler, if you make sure the bo >> + * is the one being displayed, so is properly allocated, and protected. >> + * >> + * Returns the vaddr, that you can use to write to the bo, and that you should >> + * pass to kunmap_local() when you're done with this page, or NULL if the bo >> + * is in iomem. >> + */ >> +void *ttm_bo_kmap_try_from_panic(struct ttm_buffer_object *bo, unsigned long page) >> +{ >> + if (page + 1 > PFN_UP(bo->resource->size)) >> + return NULL; >> + >> + if (!bo->resource->bus.is_iomem && bo->ttm->pages && bo->ttm->pages[page]) >> + return kmap_local_page_try_from_panic(bo->ttm->pages[page]); >> + >> + return NULL; >> +} >> +EXPORT_SYMBOL(ttm_bo_kmap_try_from_panic); >> + >> /** >> * ttm_bo_kmap >> * >> diff --git a/include/drm/ttm/ttm_bo.h b/include/drm/ttm/ttm_bo.h >> index cf027558b6db..8c0ce3fa077f 100644 >> --- a/include/drm/ttm/ttm_bo.h >> +++ b/include/drm/ttm/ttm_bo.h >> @@ -429,6 +429,7 @@ int ttm_bo_init_validate(struct ttm_device *bdev, struct ttm_buffer_object *bo, >> int ttm_bo_kmap(struct ttm_buffer_object *bo, unsigned long start_page, >> unsigned long num_pages, struct ttm_bo_kmap_obj *map); >> void ttm_bo_kunmap(struct ttm_bo_kmap_obj *map); >> +void *ttm_bo_kmap_try_from_panic(struct ttm_buffer_object *bo, unsigned long page); >> int ttm_bo_vmap(struct ttm_buffer_object *bo, struct iosys_map *map); >> void ttm_bo_vunmap(struct ttm_buffer_object *bo, struct iosys_map *map); >> int ttm_bo_mmap_obj(struct vm_area_struct *vma, struct ttm_buffer_object *bo); >
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