| Message ID | 20250321112436.1739876-2-jfalempe@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | drm/panic: Add support to scanout buffer as array of pages | expand |
On Fri, Mar 21 2025 at 12:16, Jocelyn Falempe wrote: > kmap_local_page() can be unsafe to call from a panic handler, if > CONFIG_HIGHMEM is set, and the page is in the highmem zone. > So add kmap_local_page_try_from_panic() to handle this case. I think this is a reasonable solution and the highmem case can suffer from not getting the reliable panic output. > Suggested-by: Simona Vetter <simona.vetter@ffwll.ch> > Signed-off-by: Jocelyn Falempe <jfalempe@redhat.com> > --- > include/linux/highmem-internal.h | 12 ++++++++++++ > 1 file changed, 12 insertions(+) > > diff --git a/include/linux/highmem-internal.h b/include/linux/highmem-internal.h > index dd100e849f5e0..5d089b0ca56de 100644 > --- a/include/linux/highmem-internal.h > +++ b/include/linux/highmem-internal.h > @@ -73,6 +73,13 @@ static inline void *kmap_local_page(struct page *page) > return __kmap_local_page_prot(page, kmap_prot); > } > > +static inline void *kmap_local_page_try_from_panic(struct page *page) > +{ > + if (!PageHighMem(page)) > + return page_address(page); > + return NULL; A comment explaining the reason why the highmem mapping cannot work here would be appreciated. Aside of that: Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Thanks, tglx
diff --git a/include/linux/highmem-internal.h b/include/linux/highmem-internal.h index dd100e849f5e0..5d089b0ca56de 100644 --- a/include/linux/highmem-internal.h +++ b/include/linux/highmem-internal.h @@ -73,6 +73,13 @@ static inline void *kmap_local_page(struct page *page) return __kmap_local_page_prot(page, kmap_prot); } +static inline void *kmap_local_page_try_from_panic(struct page *page) +{ + if (!PageHighMem(page)) + return page_address(page); + return NULL; +} + static inline void *kmap_local_folio(struct folio *folio, size_t offset) { struct page *page = folio_page(folio, offset / PAGE_SIZE); @@ -180,6 +187,11 @@ static inline void *kmap_local_page(struct page *page) return page_address(page); } +static inline void *kmap_local_page_try_from_panic(struct page *page) +{ + return page_address(page); +} + static inline void *kmap_local_folio(struct folio *folio, size_t offset) { return page_address(&folio->page) + offset;
kmap_local_page() can be unsafe to call from a panic handler, if CONFIG_HIGHMEM is set, and the page is in the highmem zone. So add kmap_local_page_try_from_panic() to handle this case. Suggested-by: Simona Vetter <simona.vetter@ffwll.ch> Signed-off-by: Jocelyn Falempe <jfalempe@redhat.com> --- include/linux/highmem-internal.h | 12 ++++++++++++ 1 file changed, 12 insertions(+)