On Thu, Dec 14, 2023 at 12:24:48AM +0100, Ilya Leoshkevich wrote:
> The pages for the KMSAN metadata associated with most kernel mappings
> are taken from memblock by the common code. However, vmalloc and module
> metadata needs to be defined by the architectures.
>
> Be a little bit more careful than x86: allocate exactly MODULES_LEN
> for the module shadow and origins, and then take 2/3 of vmalloc for
> the vmalloc shadow and origins. This ensures that users passing small
> vmalloc= values on the command line do not cause module metadata
> collisions.
>
> Reviewed-by: Alexander Potapenko <glider@xxxxxxxxxx>
> Signed-off-by: Ilya Leoshkevich <iii@xxxxxxxxxxxxx>
> ---
> arch/s390/boot/startup.c | 8 ++++++++
> arch/s390/include/asm/pgtable.h | 10 ++++++++++
> 2 files changed, 18 insertions(+)
>
> diff --git a/arch/s390/boot/startup.c b/arch/s390/boot/startup.c
> index 8104e0e3d188..e37e7ffda430 100644
> --- a/arch/s390/boot/startup.c
> +++ b/arch/s390/boot/startup.c
> @@ -253,9 +253,17 @@ static unsigned long setup_kernel_memory_layout(void)
> MODULES_END = round_down(__abs_lowcore, _SEGMENT_SIZE);
> MODULES_VADDR = MODULES_END - MODULES_LEN;
> VMALLOC_END = MODULES_VADDR;
> +#ifdef CONFIG_KMSAN
> + VMALLOC_END -= MODULES_LEN * 2;
> +#endif
>
> /* allow vmalloc area to occupy up to about 1/2 of the rest virtual space left */
> vmalloc_size = min(vmalloc_size, round_down(VMALLOC_END / 2, _REGION3_SIZE));
Since commit 2a65c6e1ad06 ("s390/boot: always align vmalloc area on segment boundary")
vmalloc_size is aligned on _SEGMENT_SIZE boundary.
> +#ifdef CONFIG_KMSAN
> + /* take 2/3 of vmalloc area for KMSAN shadow and origins */
> + vmalloc_size = round_down(vmalloc_size / 3, _REGION3_SIZE);
And thus, the alignment here should be _SEGMENT_SIZE as well.
> + VMALLOC_END -= vmalloc_size * 2;
> +#endif
> VMALLOC_START = VMALLOC_END - vmalloc_size;
>
> /* split remaining virtual space between 1:1 mapping & vmemmap array */
...
With the above fixup:
Acked-by: Alexander Gordeev <agordeev@xxxxxxxxxxxxx>
Thanks!
