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.vet...@ffwll.ch>
> Signed-off-by: Jocelyn Falempe <jfale...@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 <t...@linutronix.de>
Thanks,
tglx
